Topical  antiseptics , for example  dequalinium  chloride,  policresulen ,  hexetidine , or  povidone-iodine  vaginal suppositories may be applied, if the risk of ascending infections is low (outside of pregnancy and in  immunocompetent  people without histories of  upper genital tract infections ). [ 71 ]  One study found that vaginal irrigations with  hydrogen peroxide  (3%) resulted in a slight improvement, but this was much less than with the use of oral metronidazole. [ 72 ]  Intravaginal  boric acid , alone or in conjunction with other medications, may be helpful in the treatment of recurrent BV. [ 70 ] [ 73 ] [ 10 ]


TOL-463 , an  experimental  formulation of boric acid enhanced with  ethylenediaminetetraacetic acid  (EDTA), is under development as an intravaginal medication for the treatment of BV and has shown preliminary effectiveness in clinical trials. [ 74 ] [ 73 ] [ 75 ] [ 76 ]


BV is the most common infection of the vagina in women of reproductive age. [ 5 ]  The percentage of women affected at any given time varies between 5% and 70%. [ 11 ]  BV is most common in parts of Africa, and least common in Asia and Europe. [ 11 ]  In the United States, about 30% of those between the ages of 14 and 49 are affected. [ 18 ]  Rates vary considerably between ethnic groups within a country. [ 11 ]


The  Nugent Score  is a  Gram stain  scoring system for vaginal swabs to diagnose bacterial  vaginosis (BV) . The Nugent score is calculated by assessing for the presence of large  Gram-positive   rods  ( Lactobacillus  morphotypes; decrease in  Lactobacillus  scored as 0 to 4), small Gram-variable rods ( Gardnerella vaginalis  morphotypes; scored as 0 to 4), and curved Gram-variable rods ( Mobiluncus  spp. morphotypes; scored as 0 to 2). A score of 7 to 10 is consistent with bacterial vaginosis without culture. The Nugent Score is now rarely used by physicians due to the time it takes to read the slides and requires the use of a trained microscopist. [ 1 ]  Bacterial vaginosis diagnosis is done by evaluating the pH, the presences of   Lactobacillus  spp.  versus a mixed flora consisting of  Gardnerella vaginalis ,  Bacteroides  spp,  Mobiluncus  spp, and  Mycoplasma hominis .  The Amsel Criteria for bacterial vaginosis includes pH, evaluating the presence of clue cells, white discharge and an odor of amines after mixing with KOH. [ 2 ]


Prior to the development of Nugent score, assessment of bacterial vaginosis was based on culturing  G. vaginalis,  examining a  gram stain  of  vaginal discharge  and  gas chromatography . [ 3 ]


A score of 0-10 is generated from combining three other scores.  The scores are as follows: [ 3 ]


At least 10–20 high power (1000× oil immersion) fields are counted and an average determined.


Lactobacillus morphotypes — average per high powered (1000× oil immersion) field. View multiple fields.


Gardnerella  /  Bacteroides  morphotypes — average per high powered (1000× oil immersion) field. View multiple fields.


Curved Gram variable rods — average per high powered (1000× oil immersion) field. View multiple fields (note that this factor is less important — scores of only 0–2 are possible)


The scoring system was proposed by Robert P Nugent in 1991. In the study, vaginal swabs were obtained from pregnant women. [ 3 ]


Actinomyces naeslundii  is a  Gram-positive , rod-shaped  bacterium  found in the mouth of humans. The species has been implicated in  periodontal disease , as well as various  tooth cavities . [ 1 ]  In other cases,  A. naeslundii  is associated with good oral health. It is one of the first bacteria to occupy the oral cavity and colonize the  tooth 's surface. It has also been isolated from women with  bacterial vaginosis . [ 2 ]


A. naeslundii  appears  Gram-positive  and  pleomorphic  by  microscopy . It does not form spores, and is considered  anaerobic  or  microaerophilic . [ 3 ]


In 2009, the species  A. naeslundi  was split. Bacteria formerly known as " Actinomyces naeslundi  genospecies 2" were reclassified under the new species name  Actinomyces oris . Those formerly known as " Actinomyces naeslundi  genospecies WVA 963" were reclassified as  Actinomyces johnsonii . [ 3 ]


Many species of the genus  Actinomyces , including  A. naeslundii , cause a chronic disease called  actinomycosis , which is characterized by  swelling  and formation of an  abscess  which may exude  pus . This can be accompanied by  tissue fibrosis . [ 4 ]


Infections of the mouth, face, and neck are the most commonly recognized infections; however, the  thoracic region , abdomen, pelvis, and the  central nervous system  can also be involved. [ 1 ]


This  Actinomycetota -related article is a  stub . You can help Wikipedia by  expanding it .


The  Actinomycetota  (or  Actinobacteria ) are a diverse phylum of  Gram-positive bacteria  with high  GC content . [ 4 ]  They can be  terrestrial  or  aquatic . [ 5 ]  They are of great importance to land  flora  because of their contributions to  soil  systems. In soil they help to  decompose  the  organic matter  of dead organisms so the molecules can be taken up anew by  plants . While this role is also played by  fungi , Actinomycetota are much smaller and likely do not occupy the same  ecological niche . In this role the  colonies  often grow extensive  mycelia , as fungi do, and the name of an important order of the phylum,  Actinomycetales  (the actinomycetes), reflects that they were long believed to be fungi. Some soil actinomycetota (such as  Frankia ) live  symbiotically  with the plants whose  roots  pervade the soil,  fixing nitrogen  for the plants in exchange for access to some of the plant's  saccharides . Other species, such as many members of the genus  Mycobacterium , are important  pathogens .


Beyond the great interest in Actinomycetota for their soil role, much is yet to be learned about them. Although currently understood primarily as soil bacteria, they might be more abundant in fresh waters. [ 6 ]  Actinomycetota is one of the dominant bacterial phyla and contains one of the largest of bacterial genera,  Streptomyces . [ 7 ]   Streptomyces  and other actinomycetota are major contributors to biological  buffering  of soils. [ 8 ]  They are also the source of many  antibiotics . [ 9 ] [ 10 ]


The Actinomycetota genus  Bifidobacterium  is the most common bacteria in the  microbiome  of human infants. [ 11 ]  Although adults have fewer bifidobacteria, intestinal bifidobacteria help maintain the mucosal barrier and reduce  lipopolysaccharide  in the intestine. [ 12 ]


Although some of the largest and most complex bacterial cells belong to the Actinomycetota, the group of marine Actinomarinales has been described as possessing the smallest free-living  prokaryotic  cells. [ 13 ]


Some  Siberian  or  Antarctic  Actinomycetota are said to be the oldest living organism on Earth, frozen in permafrost at around half a million years ago. [ 14 ] [ 15 ]  The symptoms of life were detected by CO 2  release from permafrost samples 640 kya or younger. [ 16 ]


Most Actinomycetota of medical or economic significance are in class  Actinomycetia , and belong to the order  Actinomycetales . While many of these cause disease in humans,  Streptomyces  is notable as a source of  antibiotics . [ 10 ]


Of those Actinomycetota not in the Actinomycetales,  Gardnerella  is one of the most researched. Classification of  Gardnerella  is controversial, and  MeSH  catalogues it as both a Gram-positive and  Gram-negative  organism. [ 17 ]


Actinomycetota, especially  Streptomyces  spp., are recognized as the producers of many bioactive metabolites that are useful to humans in medicine, such as antibacterials, [ 18 ]  antifungals, [ 19 ]  antivirals, antithrombotics, immunomodifiers, antitumor drugs, and enzyme inhibitors; and in agriculture, including insecticides, herbicides, fungicides, and growth-promoting substances for plants and animals. [ 20 ]  Actinomycetota-derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines, etc. [ citation needed ]


Actinomycetota have high  guanine and cytosine content  in their  DNA . [ 21 ]  The G+C content of Actinomycetota can be as high as 70%, though some may have a low G+C content. [ 22 ]


Analysis of  glutamine synthetase  sequence has been suggested for phylogenetic analysis of the Actinomycetota. [ 23 ]


Rubrobacteria


Thermoleophilia


Coriobacteriia


Acidimicrobiia


Nitriliruptoria


Actinomycetia


Chloroflexota


"Humimicrobiia"


"Aquicultoria"


"Geothermincolia"


Nitriliruptoridae


Actinobacteridae


The currently accepted taxonomy is based on the  List of Prokaryotic names with Standing in Nomenclature  (LPSN) [ 2 ]  and  National Center for Biotechnology Information  (NCBI). [ 31 ]


Aggregatibacter actinomycetemcomitans  is a  Gram-negative , facultative anaerobe, nonmotile bacterium that is often found in association with  localized aggressive periodontitis , a severe infection of the  periodontium . It is also suspected to be involved in  chronic periodontitis . [ 1 ]   Less frequently,  A. actinomycetemcomitans  is associated with nonoral infections such as endocarditis. Its role in aggressive  periodontitis  was first discovered by  Danish -born  periodontist   Jørgen Slots , a professor of  dentistry  and  microbiology  at the  University of Southern California School of Dentistry . [ citation needed ]


'Bacterium actinomycetem comitans' was first described by Klinger (1912) as coccobacillary bacteria isolated  with  Actinomyces  from actinomycotic lesions in humans. It was reclassified as  Actinobacillus actinomycetemcomitans  by Topley & Wilson (1929) and as  Haemophilus actinomycetemcomitans  by Potts  et al.  (1985). The species has attracted attention because of its association with localized aggressive periodontitis. [ 2 ]


Recent studies have shown a phylogenetic similarity of  A. actinomycetemcomitans  and  Haemophilus aphrophilus ,  H. paraphrophilus , and  H. segnis , suggesting the new  genus   Aggregatibacter  for them. [ 2 ]


It is one of the  bacteria  that might be implicated in destructive  periodontal disease . Although it has been found more frequently in localized aggressive periodontitis, [ 3 ]  prevalence in any population is rather high. It has also been isolated from actinomycotic lesions (mixed infection with certain  Actinomyces  species, in particular  A. israelii ). It possesses certain  virulence  factors that enable it to invade tissues, such as the pore-forming toxin leukotoxin A. It has also been isolated from women with  bacterial vaginosis  and as an etiologic agent in endocarditis. [ 4 ]  The pore-forming toxin LtxA of  A. actinomycetemcomitans  may be a trigger of the autoimmune disease  rheumatoid arthritis  due to its ability to stimulate protein  citrullination , a post-translational protein modification targeted by autoantibodies in this disease. [ 5 ] [ 6 ]


In bacteria,  small RNAs  are involved in gene regulation. Jorth et al. identified 9 sRNA by Northern blotting from computer-predicted candidates in strain VT1169 and 202 sRNA by RNA seq in strain 624. [ 8 ] [ 9 ]  A systematic screen by RNA-seq and RT-PCR in HK1651 strain (a clinical isolate from an aggressive  periodontitis patient), quantified 70 sRNAs and further identified 17 differentially expressed sRNAs during growth phases. [ 10 ]  Target prediction indicated possibility of sRNA interaction with several virulence genes.  [ 10 ]  This study confirmed the presence of one of previously identified Fur regulated  sRNAs JA04  identified in strain HK1651. [ citation needed ]


Anaerococcus  is a genus of bacteria. Its type species is  Anaerococcus prevotii . [ 1 ]  These bacteria are Gram-positive and strictly anaerobic. [ 2 ] [ 3 ] [ 4 ]  The genus Anaerococcus was proposed in 2001. [ 2 ] [ 4 ]  Its genome was sequenced in August 2009. The genus Anaerococcus is one of six genera classified within the group GPAC (Gram-Positive Anaerobic Cocci). [ 5 ]  These six genera ( Peptostreptococcus ,  Peptoniphilus ,  Parvimonas ,  Finegoldia ,  Murdochiella , and Anaerococcus) are found in the human body as part of the commensal human microbiota. [ 6 ] [ 7 ] [ 5 ]


It is commonly found in the human  microbiome  and is associated with various infections. [ 8 ]  Most of the species in this genus can be found among microbes of the skin, human vagina, nasal cavity, oral cavity and feces, often as a pathogen found in  ovarian   abscesses ,  chronic wounds  and  vaginal discharge . [ 9 ]  Moreover, some of the species can be isolated from  foot ulcers  and  knee arthritis . [ 2 ]  It can be present in  urinary tract infections ,  chronic ulcers ,  pleural empyema ,  blood infections , and soft tissue  infections . It is involved in polymicrobial infections. [ 10 ]  Strains of Anaerococcus were found in the armpit microbiota suggesting some species in this genus could play a role in axillary odor. [ 10 ] [ 11 ]


The genus Anaerococcus are non motile bacteria who can not form spores. [ 4 ] [ 12 ] [ 2 ]  Depending on the species the arrangement can be different. The most common arrangements within this genus are pairs, tetrads, short chains and irregular formations. [ 10 ] [ 4 ]  Their cells size can differ from 0.6μm to 0.9μm. [ 10 ]  However, when they are grown using enrinched blood agar their size can go from 0.5μm to 2μm. [ 10 ]  In this genus, there are more than one major cellular fatty acids:  C18:1 ,  C16:1 ,  C18  and  C16 . [ 12 ]  Most species in this genus are indole-negative and coaguase-negative. [ 10 ]  In general, the species of Anaerococcus presents susceptibility to penicillins but are resistant to  tetracycline ,  erythromycin  and  clindamycin . [ 9 ]


The genus Anaerococcus are classified as  saccharolytic  bacteria. [ 2 ] [ 13 ]  Its species can be arranged from weakly saccharolytic (ex.  A. prevotii ,  A. lactolyticus ) to strongly saccharolytic (ex.  A. hydrogenalis ). [ 13 ]  This genus can ferment carbohydrates weakly. [ 6 ]  The major sources of energy use in the metabolism of Anaerococcus are peptones and aminoacids. [ 4 ] [ 10 ]  The three major sugars fermented within this genus are glucose, mannose, fructose and sucrose. [ 12 ] [ 4 ]  After fermenting the sugars, Anaerococcus produce weak acids as their metabolic end product. [ 13 ]  Within these metabolic end products, this genus ca produce butyric acid, lactic acid, and some propionic and succinic acid. [ 12 ]   Nonetheless, the major metabolite produced by Anaerococcus is butyrate. [ 13 ] [ 10 ] [ 2 ]


Until recently, the genus Anaerococcus have 14 known species. [ 14 ] [ 9 ]  Six of the species were initially classified in the genus Peptostreptococcus but then based on their characteristics were re-classified in the new genus Anaerococcus:  A. hydrogenalis ,  A. lactolyticus ,  A. octavius ,  A. prevotii ,  A. tetradius , and  A. vaginalis. [ 5 ] [ 2 ]  Throughout the years, the specie who has been more commonly found on the body within this genus is  A. prevotii. [ 9 ]


Contrary to most of the species in the genus,  Anaerococcus octavius  was not related to human infections. [ 9 ]  Nevertheless, recently a new case revealed  A. octavius  can cause  bacteremia . [ 9 ]  Even though it is uncommon,  Anaerococcus octavius  can be the cause for human infections. [ 9 ]  Other studies have found  A. octavius  as part of the nasal, skin and vaginal normal flora. [ 9 ] [ 4 ]  This bacteria can ferment ribose, glucose, and mannose. [ 4 ]


A. prevotii  is normally found in vaginal discharge, human plasma and some types of abscesses - such as ovarian, peritoneal sacral and/or lung abscesses. [ 9 ] [ 6 ]   Anaerococcus prevotii  is part of the normal flora in the skin, oral cavity and the gut. [ 6 ]  Studies has shown  Anaerococcus prevotii  presents resistance to  Ceftazidime ,  Clindamycin ,  Levofloxacin . [ 9 ]  Unlike the other species,  A. prevotii  can not ferment glucose. [ 15 ]


A. vaginalis  was first recovered from vaginal discharges and ovarian abscesses although this bacteria can also be found in pressure ulcers and diabetic foot. [ 4 ] [ 9 ]  Some strains from this species can be indole-positive. [ 4 ]


A. provencensis  was isolated from a cervical abscess. [ 16 ]  This species can ferment lactose, unlike  A. tetradius, A. prevotii,  and  A. octavius . [ 16 ]  The first analysis made on  Anaerococcus provencensis  showed it is susceptible to  penicillin G ,  imipenem ,  amoxillin ,  metronidazole ,  cefotetan  and  vancomycin . [ 16 ]


A. senegalensis  is one of the few species in the genus whose genome has been sequenced. [ 2 ]  The genome has a size of 1,790,835  bp . [ 2 ]  Analysis did not show presence of a plasmid. [ 2 ]  Initially,  Anaerococcus senegalensis  was found in the fecal flora of a healthy person. [ 2 ]


A.   rubiinfantis  was discovered from a stool sample taken from an infant with severe acute malnutrition in Senegal. [ 17 ]  Based on a genomic analysis,  Anaerococcus rubiinfantis  has high antibiotic susceptibility. [ 17 ]  For that reason this bacteria can be treated with common oral antibiotics. [ 17 ]   A.   rubiinfantis  have catalase activity, which is not common from an anaerobic bacteria. [ 17 ]


A. marasmi  was first found in 2016 from a stool sample on a child with  marasmus . [ 14 ]  Just like  A. rubiinfantis, Anaerococcus marasmi  is catalase positive. [ 14 ]   A. marasmi  can grow in a range of pH between 6.5 and 8. [ 14 ]  Moreover,  A. marasmi  has a high 16S rRNA sequence similarity (97.6%) with  A. prevotii   [ 14 ]


A. urinomassiliensis  was isolated from a urine sample of a male adolescent with  membranoproliferative glomerulonephritis  and  autoimmune hepatitis . [ 18 ]  It took 10 days of anaerobic incubation to observe growth from this bacteria. [ 18 ]  Anaerococcus urinomassiliensis does not have either oxidase or catalase activity. [ 18 ]


Fannyhessea vaginae  is a species of  bacteria  in the family  Atopobiaceae . It is a facultative  anaerobic ,  Gram-positive  rod-shaped or elliptical  coccobacillus  found as single elements or in pairs or short chains. [ 2 ]  It is typically isolated from 80% of women with  bacterial vaginosis  and it is implicated in treatment failures. [ 3 ] [ 4 ]  Invasive infections such as bacteremia have been reported. [ 5 ]


Bacterial vaginosis  is caused by an imbalance of the  naturally occurring bacteria in the vagina . [ 1 ] [ 2 ]   The normally predominant species of  Lactobacilli  are markedly reduced. [ 3 ]  This is the list of organisms that are found in the vagina that are associated with  bacterial vaginosis , an infectious  disease  of the  vagina  caused by excessive growth of specific  bacteria . [ 4 ] [ 5 ]  The census and relationships among the microbiota are altered in BV, resulting in a complex bacterial milieu. Some species have relatively been identified recently. [ 6 ]  Having infections with the listed pathogens increases the risk of acquiring other  sexually transmitted infections  including  HIV/AIDS . [ 7 ] [ 8 ]


Bacteroides ureolyticus  is a species in the bacterial  genus  of  Gram-negative ,  obligately anaerobic   bacteria .  Bacteroides  species are non- endospore -forming  bacilli , and may be either  motile  or non-motile, depending on the species. [ 1 ]  The DNA base composition is 40–48%  GC .


Bacteroides  are normally  mutualistic , a substantial portion of the mammalian  gastrointestinal flora , [ 2 ]  and they process complex molecules into simpler ones. [ 3 ] [ 4 ] [ 5 ]  As many as 10 10 -10 11  cells per gram of human feces have been reported. [ 6 ]  They can use  simple sugars  when available; however, the main sources of energy for  Bacteroides  species in the gut are complex host-derived and plant  glycans . [ 7 ]


Bacteroides ureolyticus  has been isolated from pregnant women with symptoms of  bacterial vaginosis . [ 8 ]


See text.


Bifidobacterium  is a  genus  of  gram-positive ,  nonmotile , often branched  anaerobic   bacteria .  They are ubiquitous inhabitants of the  gastrointestinal tract [ 2 ] [ 3 ]  though strains have been isolated from the  vagina [ 4 ]  and mouth ( B. dentium ) of mammals, including humans.  Bifidobacteria are one of the major genera of bacteria that make up the gastrointestinal tract  microbiota  in mammals. Some bifidobacteria are used as  probiotics .


Before the 1960s,  Bifidobacterium  species were collectively referred to as  Lactobacillus bifidus .


In 1899,  Henri Tissier , a French  pediatrician  at the  Pasteur Institute  in Paris, isolated a bacterium characterised by a Y-shaped morphology ("bifid") in the intestinal microbiota of breast-fed infants and named it "bifidus". [ 5 ]  In 1907,  Élie Metchnikoff , deputy director at the Pasteur Institute, propounded the theory that  lactic acid  bacteria are beneficial to human health. [ 5 ]  Metchnikoff observed that the  longevity  of Bulgarians was the result of their consumption of  fermented milk products . [ 6 ]  Metchnikoff also suggested that "oral administration of cultures of fermentative bacteria would implant the beneficial bacteria in the intestinal tract". [ 7 ]


The genus  Bifidobacterium  possesses a unique  fructose-6-phosphate phosphoketolase  pathway employed to ferment  carbohydrates . [ citation needed ]


Much metabolic research on bifidobacteria has focused on  oligosaccharide  metabolism, as these carbohydrates are available in their otherwise nutrient-limited habitats. Infant-associated bifidobacterial  phylotypes  appear to have evolved the ability to ferment  milk oligosaccharides , whereas adult-associated species use plant oligosaccharides, consistent with what they encounter in their respective environments. As breast-fed infants often harbor bifidobacteria-dominated gut consortia, numerous applications attempt to mimic the bifidogenic properties of milk oligosaccharides. These are broadly classified as plant-derived  fructooligosaccharides  or dairy-derived  galactooligosaccharides , which are differentially metabolized and distinct from milk oligosaccharide  catabolism . [ 3 ]


The sensitivity of members of the genus  Bifidobacterium  to O 2  generally limits probiotic activity to anaerobic habitats. Recent research has reported that some  Bifidobacterium  strains exhibit various types of  oxic  growth. Low concentrations of O 2  and CO 2  can have a stimulatory effect on the growth of these  Bifidobacterium  strains. Based on the growth profiles under different O 2  concentrations, the  Bifidobacterium  species were classified into four classes: O 2 -hypersensitive, O 2 -sensitive, O 2 -tolerant, and  microaerophilic . The primary factor responsible for aerobic growth inhibition is proposed to be the production of  hydrogen peroxide  (H 2 O 2 ) in the growth medium. A H 2 O 2 -forming  NADH   oxidase  was purified from O 2 -sensitive  Bifidobacterium bifidum  and was identified as a  b -type  dihydroorotate dehydrogenase . The kinetic parameters suggested that the enzyme could be involved in H 2 O 2  production in highly aerated environments. [ 8 ]


Members of the genus  Bifidobacterium  have genome sizes ranging from 1.73 ( Bifidobacterium indicum ) to 3.25 Mb ( Bifidobacterium biavatii ), corresponding to 1,352 and 2,557 predicted protein-encoding  open reading frames , respectively. [ 9 ]


Functional classification of  Bifidobacterium  genes, including the  pan-genome  of this genus, revealed that 13.7% of the identified bifidobacterial genes encode enzymes involved in  carbohydrate metabolism . [ 9 ]


Adding  Bifidobacterium  as a probiotic to conventional treatment of  ulcerative colitis  has been shown to be associated with improved rates of remission and improved maintenance of remission. [ 10 ]  Some  Bifidobacterium  strains are considered as important probiotics and used in the food industry. Different species and/or strains of bifidobacteria may exert a range of beneficial health effects, including the regulation of intestinal microbial  homeostasis , the inhibition of pathogens and harmful bacteria that colonize and/or infect the gut mucosa, the modulation of local and systemic immune responses, the repression of procarcinogenic enzymatic activities within the microbiota, the production of vitamins, and the bioconversion of a number of dietary compounds into bioactive molecules. [ 3 ]  Bifidobacteria improve the gut mucosal barrier and lower levels of  lipopolysaccharide  in the intestine. [ 11 ]


Bifidobacteria may also improve abdominal pain in patients with  irritable bowel syndrome  (IBS) though studies to date have been inconclusive. [ 12 ]


Naturally occurring  Bifidobacterium  spp. may discourage the growth of  Gram-negative  pathogens in infants. [ 13 ]


A mother's milk contains high concentrations of lactose and lower quantities of phosphate ( pH buffer ). Therefore, when mother's milk is fermented by lactic acid bacteria (including bifidobacteria) in the infant's gastrointestinal tract, the pH may be reduced, making it more difficult for Gram-negative bacteria to grow. [ citation needed ]


The human infant gut is relatively sterile up until birth, where it takes up bacteria from its surrounding environment and its mother. [ 14 ]  The  microbiota  that makes up the infant gut differs from the adult gut. An infant reaches the adult stage of their microbiome at around three years of age, when their microbiome diversity increases, stabilizes, and the infant switches over to solid foods. Breast-fed infants are colonized earlier by  Bifidobacterium  when compared to babies that are primarily formula-fed. [ 15 ]   Bifidobacterium  is the most common bacteria in the infant gut microbiome. [ 16 ]  There is more variability in  genotypes  over time in infants, making them less stable compared to the adult  Bifidobacterium . Infants and children under three years old show low diversity in microbiome bacteria, but more diversity between individuals when compared to adults. [ 17 ]   Reduction of  Bifidobacterium  and increase in diversity of the infant gut microbiome occurs with less breast-milk intake and increase of solid food intake. Mammalian milk all contain  oligosaccharides  showing natural selection  [ clarification needed ] . Human milk oligosaccharides are not digested by enzymes and remain whole through the digestive tract before being broken down in the colon by microbiota.  Bifidobacterium  species genomes of  B. longum , B. bifidum,  B. breve  contain genes that can hydrolyze some of the human milk oligosaccharides and these are found in higher numbers in infants that are breast-fed.  Glycans  that are produced by the humans are converted into food and energy for the  B. bifidum.  showing an example of  coevolution . [ 18 ]


The genus  Bifidobacterium  comprises the following species: [ 19 ]


The  Clostridia  are a highly  polyphyletic  class of  Bacillota , including  Clostridium  and other similar genera.  They are distinguished from the  Bacilli  by lacking  aerobic respiration . They are  obligate anaerobes  and oxygen is toxic to them. Species of the class Clostridia are often but not always  Gram-positive  (see  Halanaerobium ) and have the ability to form spores. [ 1 ]  Studies show they are not a  monophyletic  group, and their relationships are not entirely certain. Currently, most are placed in a single order called Clostridiales, but this is not a natural group and is likely to be redefined in the future.


Most species of the genus  Clostridium  are  saprophytic  organisms that ferment plant polysaccharides  [ 2 ]  and are found in many places in the environment, most notably the soil. However, the genus does contain some human pathogens (outlined below).
The toxins produced by certain members of the genus  Clostridium  are among the most dangerous known. Examples are tetanus toxin (known as  tetanospasmin ) produced by  C. tetani  and  botulinum toxin  produced by  C. botulinum .  Some species have been isolated from women with  bacterial vaginosis . [ 3 ]


Notable species of this class include: [ citation needed ]


Heliobacteria  and  Christensenella  are also members of the class Clostridia.


Some of the enzymes produced by this group are used in  bioremediation .


The currently accepted taxonomy based on the  List of Prokaryotic names with Standing in Nomenclature  (LPSN) [ 4 ]  and the  National Center for Biotechnology Information  (NCBI). [ 5 ]


Dictyoglomota


" Caldicellulosiruptorales "


" Thermosediminibacteria " [incl. "Ammonificales", DSM-22653]


" Thermoanaerobacteria " [incl.  Thermanaeromonas ,  Desulfovirgula ]


" Sulfobacillia "


" Thermaerobacteria "


" Carboxydothermales "


" Thermacetogeniales "


Moorellales  {"Moorellia"}


" Calderihabitantales "


" Koleobacterales "


Zhaonellaceae


" Desulfitibacterales "


" Syntrophomonadia "


Gelria  ♦


" Symbiobacteriia " ♦


Actinomycetota


Nitrospirota


" Thermodesulfobiota "  ♦


Elusimicrobiota


" Halanaerobiia " ♦


Acidobacteriota


Chitinivibrionia


" Planctobacteria


Thermolithobacteria


" Carboxydocellales "


" Thermincolia "


" Desulfofundulaceae "


" Selenomonadia "


Limnochordia


" Desulfotomaculia "


" Desulfitobacteriia "


" Peptococcia "


" Dethiobacteria "


" Natranaerobiia "


Fusobacteria  { Fusobacteriota }


Acholeplasmatales


Erysipelotrichia


Mollicutes


Bacilliia  {Bacillota s.s.}


"Clostridiia"  s.s.  (incl. Tissierellia)


♦ Paraphyletic "Clostridiia"


" Ca.   Acetocimmeria " {UBA3575}


" Symbiobacteriia "


" Hydrogenisporia " [UBA4882]


" Proteinivoracia "


" Bacillia " (incl.  Erysipelotrichia ,  Mollicutes )


Selenomonadia


" Dehalobacteriia "


" Thermacetogeniales " {DSM-12270}


" Moorellia "


" Carboxydocellales " {GCA-003054495}


" Carboxydothermales " {Z-2901}


" Thermosediminibacteria "


" Thermoanaerobacteria "


Clostridiia  s.s.  (incl. Tissierellia)


Since they are commonly found in soils and in microbiota of humans and animals, Clostridia wounds and infections are found worldwide. Host defenses against the microbe are nearly absent, and very little innate immunity exists, if any. Clostridia can be diagnosed by recognizing the characteristics of the lesion of the infection along with Gram stains of the tissue and bacterial culture. [ 1 ]  Although the body does not have adequate defenses alone, this microbe can be controlled with the help of antibiotics, like penicillin, and tissue  debridement  for the more severe cases. [ citation needed ]


Clostridia bacteria are commonly found in the  gut microbiome . [ medical citation needed ]


Overuse of antibiotics can cause imbalance of the gut microbiome, leading to overgrowth of the species  Clostridioides difficile  causing a  serious infection  (CDI). [ 12 ]  Effects of this infection include severe diarrhea and the severity of many bowel related diseases is also increased as a result of the infection. Other  Clostridium  bacteria in the gut have been linked to brain connectivity and healthy function. [ 13 ]


Patients that have been subjected to  fecal microbiota transplants  to treat their CDI have seen improvements in their mood and  mental health . [ 12 ]  This preliminary research seems to suggest a tentative link between the presence of  Clostridia  in the gut microbiome and overall mental health, with gut microbiome transplants as an avenue of future research into novel treatments for certain psychiatric disorders. [ citation needed ]


A  douche  is a term for a device used to introduce a stream of water into the body for medical or hygienic reasons, or for the stream of water itself. Douche usually refers to vaginal irrigation, the rinsing of the  vagina , but it can also refer to the rinsing of any body cavity. A douche bag is a piece of equipment for douching—a bag for holding the fluid used in douching. To avoid transferring intestinal bacteria to the vagina, the same bag must not be used for both an  enema  and a vaginal douche.


Douching after sexual intercourse is not an effective form of  birth control . [ 1 ]  Additionally, douching is associated with a number of health problems, including  cervical cancer ,  pelvic inflammatory disease ,  endometritis , and increased risk of  sexually transmitted infections . [ 2 ]


The word's first known use is in 1766.  Douche  came into English via  French , from  Italian :  doccia  "conduit pipe" and  docciare  "pour by drops" to douche, from  doccia  water pipe, probably back-formation from  doccione  conduit, from  Latin :  duction- ,  ductio  means of conveying water, from  ducere  to lead. [ 3 ] [ failed verification ]  In French today it means  shower , as it does in many European languages.


Vaginal douches  may consist of water, water mixed with  vinegar , or even  antiseptic  chemicals. Douching has been touted as having a number of supposed but unproven benefits. In addition to promising to clean the vagina of unwanted odors, it can also be used by women who wish to avoid smearing a sexual partner's penis with menstrual blood while having  sexual intercourse during menstruation . In the past, douching was also used after intercourse as a method of  birth control , though it is not effective (see below).


Many health-care professionals state that douching is dangerous, as it interferes with both the vagina's normal self-cleaning and with the natural bacterial culture of the vagina, and it might spread or introduce infections. Douching is implicated in a wide variety of dangers, including: adverse pregnancy outcomes including  ectopic pregnancy ,  low birth weight , preterm labor,  preterm birth , and  chorioamnionitis ; serious gynecologic outcomes, including increased risk of  cervical cancer ,  pelvic inflammatory disease ,  endometritis , and increased risk for  sexually transmitted infections , including  HIV ; it also predisposes women to develop  bacterial vaginosis  (BV), [ 4 ]  which is further associated with adverse pregnancy outcomes and increased risk of sexually transmitted infections. [ 5 ]  Due to this, the  U.S. Department of Health and Human Services  strongly discourages douching, citing the risks of irritation, bacterial vaginosis, and pelvic inflammatory disease (PID). Frequent douching with water may result in an imbalance of the  pH  of the vagina, and thus may put women at risk for possible vaginal infections, especially yeast infections. [ 6 ]


In May 2003, a randomized, controlled, multi-center study was conducted with 1827 women ages 18–44 who were regular users of a douche product and who had been treated recently for a sexually transmitted bacterial infection or bacterial vaginosis. Women were randomly assigned to use either a newly designed and marketed douche product or a soft cloth towelette. There was little or no indication of a greater risk of PID among women assigned to use the douche product (versus soft cloth towelette). [ 7 ]


Antiseptics used during douching disturb the natural balance of bacteria in the vagina and can cause infections. [ 8 ]  Unclean douching equipment may introduce foreign bodies into the vagina. Douching may also wash bacteria into the  uterus  and  fallopian tubes , causing fertility problems. [ 9 ]  For these reasons, the practice of douching is now strongly discouraged except when ordered by a physician for medical reasons. [ 8 ]


Douching after intercourse is estimated to reduce the chances of conception by only about 30%. [ 10 ]  In comparison, proper male  condom  use reduces the chance of conception by as much as 98%. [ 11 ]  In some cases douching may force the  ejaculate  further into the vagina, increasing the chance of pregnancy. A review of studies by researchers at the  University of Rochester Medical Center  (N.Y.) showed that women who douched regularly and later became pregnant had higher rates of  ectopic pregnancy ,  infections , and low birth weight infants than women who only douched occasionally or who never douched. [ 8 ]


A 1995 survey quoted in the  University of Rochester  study found that 27% of U.S. women age 15 to 44 douched regularly, but that douching was more common among  African-American  women (over 50%) than among white women (21%), [ 8 ]  and frequent douching contributes to more frequent bacterial vaginosis among African-American women than the average. [ 4 ]


Medical doctor  Harriet Hall  writes that not only can douching change the  pH  of the vagina and lead to infections, "There is no need ... to cleanse the vagina. It cleanses itself". [ 12 ]


Douchebag  and its variants, or simply  douche , [ 13 ] [ 14 ]  are  pejorative  terms [ 14 ]  referring to an arrogant, obnoxious, or despicable person. [ 15 ]  The slang usage of the term originated in the 1960s. [ 16 ]


Eggerthella  is a bacterial  genus  of  Actinomycetota , in the family  Coriobacteriaceae . Members of this genus are  anaerobic ,  non-sporulating , non-motile,  Gram-positive   bacilli  that grow singly, as pairs, or in short chains. They are found in the human  colon  and feces and have been implicated as a cause of  ulcerative colitis , liver and anal abscesses and systemic bacteremia. [ 2 ] [ 3 ]


The type strain for this genus,  Eggerthella lenta , was known as  Eubacterium lentum  prior to 1999. [ 4 ] [ 5 ]   The genus is named for Arnold Eggerth, who first described the organism in 1935. [ 6 ]


Eggerthella  has not been characterized well because of identification difficulties. It is an emerging pathogen that is likely to be studied and recognized more in years to come. It has a tendency to cause disease that spreads throughout the body. [ 7 ]


The currently accepted taxonomy is based on the  List of Prokaryotic names with Standing in Nomenclature  (LPSN) [ 1 ]  and  National Center for Biotechnology Information  (NCBI). [ 8 ]


E. sinensis


E. timonensis


E. guodeyinii


E. lenta


E. sinensis   Lau et al. 2006


E. lenta   (Eggerth 1935) Wade et al. 1999


E. guodeyinii   Ge et al. 2021


E. timonensis   Bilen et al. 2023


Eubacterium  is a genus of  Gram-positive bacteria  in the family  Eubacteriaceae . These bacteria are characterised by a rigid  cell wall . They may either be motile or nonmotile. If motile, they have a  flagellum . A typical flagellum consists of a basal body, filament, and hook. The long filament is the organ which helps eubacteria move. [ citation needed ] [ citation needed ]


This  Clostridiales -related article is a  stub . You can help Wikipedia by  expanding it .


Fusobacterium nucleatum  is a  Gram-negative ,  anaerobic   bacterium ,  commensal  to the human  oral cavity , that plays a role in  periodontal disease . This organism is commonly recovered from different monocultured microbial and mixed infections in humans and animals. In health and disease, it is a key component of periodontal  plaque  due to its abundance and its ability to coaggregate with other bacteria species in the oral cavity. [ 1 ] [ 2 ]


Research implicates periodontal disease caused by  F. nucleatum  with  preterm births  in humans. In many studies,  F. nucleatum  cells have been isolated from the  amniotic fluid ,  placenta , and  chorioamnionic membranes  of women  delivering prematurely . Moreover, laboratory mice intravenously inoculated with  F. nucleatum  have been found to deliver prematurely, and the pathology of the infection seems to mirror observations in humans. [ 3 ]  Together, this research provides evidence for a possible causal connection between  F. nucleatum -caused periodontal disease and at least some cases of preterm delivery.  F. nucleatum  can also be isolated from the  vaginal microbiome , especially in women with a condition known as  bacterial vaginosis . [ 4 ]  Both  F. nucleatum  vaginal colonization and bacterial vaginosis also have been linked with preterm birth and infections within the uterus. [ 5 ]  Thus, preterm birth arising by infections caused by  F. nucleatum  could also arise from invasive infection into the uterine tissue originating from the colonized vagina. [ citation needed ]


F. nucleatum  has a demonstrated association with  colorectal cancer .  Fusobacterium  species have been found at higher quantities in certain types of colon tumors than in surrounding colon tissue or the colons of healthy individuals, but whether this is an indirect correlation or a causal link is unclear. A distinguishing mechanism has been described by which  F. nucleatum  creates a pro- inflammatory  environment which is conducive to  tumor  growth through the recruitment of  tumor-infiltrating immune cells , which, unlike other bacteria linked to colorectal carcinoma, does not exacerbate other pathological processes such as  colitis ,  enteritis  and inflammatory-associated intestinal carcinogenesis. This suggests direct and specific carcinogenesis. [ 6 ]   F. nucleatum  can bind to host tissue  E-cadherins  via a FadA, an outer membrane protein. [ 7 ]  Additionally, a surface expressed  lectin  called Fap2 mediates  F. nucleatum  adherence to colorectal cancer cells that express  Gal/GalNAc  moieties on their surface. Binding via Fap2 has also been shown to up-regulate production of  cytokines  associated with higher rates of  metastasis . [ 8 ]


Type IV pili  facilitate  natural competence  in  F. nucleatum . [ 9 ]   Natural competence involves three principal stages: (1) Uptake of exogenous  DNA  and transport to the cytoplasm, (2) homologous DNA that has been taken up can integrate into the recipient cell genome by  homologous recombination , and (3) the integrated exogenous DNA can express  gene  functions. [ 9 ]


Gardnerella vaginalis  is a  species  of  Gram-variable -staining  facultative anaerobic   bacteria . The organisms are small (1.0–1.5 μm in diameter) non-spore-forming, nonmotile  coccobacilli . [ 3 ]


Once classified as  Haemophilus vaginalis  and afterwards as  Corynebacterium vaginalis ,  G. vaginalis  grows as small, circular, convex, gray colonies on  chocolate agar ; it also grows on  HBT [ 4 ]  agar. A selective medium for  G. vaginalis  is  colistin - oxolinic acid  blood agar.


G. vaginalis  is a facultatively anaerobic Gram-variable rod that is involved, together with many other bacteria, mostly anaerobic, in  bacterial vaginosis  (BV) in some women as a result of a disruption in the normal  vaginal   microflora . The resident facultative anaerobic  Lactobacillus  population in the vagina is responsible for the acidic environment. Once the  anaerobes  have supplanted the normal vaginal bacteria, prescription  antibiotics  with anaerobic coverage may have to be given to re-establish the equilibrium of the  ecosystem .  G. vaginalis   is not considered the sole cause of the bacterial vaginosis, but a signal organism of the altered microbial ecology associated with overgrowth of many bacterial species. [ 5 ]


While typically isolated in  genital  cultures, it may also be detected in other samples from  blood ,  urine , and the  pharynx . Although  G. vaginalis  is a major species present in bacterial vaginosis, it can also be isolated from women without any signs or symptoms of infection. [ 6 ]


It has a Gram-positive cell wall, [ 7 ]  but, because the cell wall is so thin, it can appear either  Gram-positive  or  Gram-negative  under the microscope. It is associated microscopically with  clue cells , which are  epithelial cells  covered in bacteria. [ citation needed ]


G. vaginalis  produces a pore-forming toxin,  vaginolysin , which affects only human cells. [ 8 ]


Protease  and  sialidase  enzyme activities frequently accompany  G. vaginalis . [ 9 ] [ 10 ] [ 11 ] [ 12 ]


A variety of diagnosis techniques are currently available for identifying  Gardnerella vaginalis  such as the OSOM BV Blue assay, FemExam cards and nucleic acid amplification tests (NAATs), resulting in the determination of ongoing BV. The OSOM BV Blue Assay is a chromogenic point-of-care test which can measure  sialidase  levels in vaginal fluids. As sialidases are produced by bacteria such as  Gardnerella  and  Bacteroides  species, similar tests are useful as diagnostic techniques. [ 13 ]  FemExam, besides detecting vaginal fluid pH and trimethylamine presence, is able to measure  proline iminopeptidase  activity of  G. vaginalis . [ 14 ]  Finally, the nucleic acid amplification tests (NAATs), such as PCR, are commonly used detection techniques due to their ability to detect as little as one organism in a sample, providing a closer look to  Gardnerella vaginalis  and BV status. [ 13 ]


Bacterial vaginosis is commonly treated with topical or oral antibiotics such as metronidazole or clindamycin, which work by targeting  G. vaginalis  and possibly other anaerobic bacteria. [ 15 ]  Additionally, a study published in the Journal of Clinical Microbiology [ full citation needed ]  described the effectiveness of clindamycin in inhibiting the growth of  G. vaginalis  in vitro; it was found that clindamycin was able to inhibit the growth of the organism at concentrations as low as 0.25 μg/mL. However, due to high recurrence rates, alternative treatment options for BV are still in development. Topical boric acid has been shown to be effective against BV, due to its ability to remove BV-specific  biofilms  and enhance eradication of  G. vaginalis  and other potential bacterial pathogens, resulting in reduced recurrence of symptomatic BV. [ 16 ]   Its mechanism of action is still not fully understood, but its effects on inhibition of bacterial enzymes, biofilm formation and the permeability of bacterial cell walls, [ citation needed ]  potentially make it a useful agent for recurrent BV for further study.


G. vaginalis  is associated with bacterial vaginosis, [ 17 ]  which may be asymptomatic, [ 18 ]  or may have symptoms including vaginal discharge, vaginal irritation, and a "fish-like" odor. In the amine  whiff test , 10%  KOH  is added to the discharge; a positive result is indicated if a fishy smell is produced.  This and other tests can be used to distinguish between vaginal symptoms related to  G. vaginalis  and those caused by other organisms, such as  Trichomonas  and  Candida albicans , which are similar and may require different treatment.   Trichomonas vaginalis  and  G. vaginalis  have similar clinical presentations and can cause a frothy gray or yellow-green vaginal discharge, pruritus, and produce a positive "whiff-test".  The two can be distinguished using a wet-mount slide, where a swab of the  vaginal epithelium  is diluted and then placed onto a slide for observation under a microscope.   Gardnerella  reveals a classic " clue cell " under the microscope, showing bacteria adhering to the surface of  squamous  epithelial cells. [ 19 ]


Gardnerella vaginalis  was described in 1953 by Sidney Leopold as a nonmotile, nonencapsulated, pleomorphic gram-negative rod from the vaginas of women who showed symptoms of cervicitis. As though it's been suggested that the organism was related to the genus Haemophilus due to its morphology and growth conditions, the relation between this organism and vaginitis was still an unknown. [ 20 ]  It was in 1955, when Gardner and Dukes described the microorganism in relation to bacterial vaginosis (BV). [ 21 ]  Multiple risk factors associated with the development of BV have been identified. However, its exact etiology remains elusive due to its complexity. [ 22 ]


See text


Megasphaera  is a genus of  Bacillota   bacteria  classified within the class  Negativicutes . [ 1 ] [ 2 ]


This classification has been reexamined. [ 3 ]  It appears that this genus is a member of the  Clostridia .


The currently accepted taxonomy is based on the  List of Prokaryotic names with Standing in Nomenclature  (LPSN) [ 1 ]  and  National Center for Biotechnology Information  (NCBI) [ 2 ]


M. micronuciformis   Marchandin et al. 2003


M. hutchinsoni   Srinivasan et al. 2021


M. lornae   Srinivasan et al. 2021


M. massiliensis   Padmanabhan et al. 2016


M. elsdenii   (Gutierrez et al. 1959) Rogosa 1971


M. indica   Lanjekar et al. 2014


M. hexanoica   Jeon et al. 2017


M. hominis   Liu et al. 2022


M. paucivorans   Juvonen and Suihko 2006


M. sueciensis   Juvonen and Suihko 2006


M. cerevisiae   Engelmann and Weiss 1986


M. vaginalis   Srinivasan et al. 2021 non Bordigoni et al. 2020


Anaeroglobus geminatus   Carlier et al. 2002


" M. butyrica "  Hitch et al. 2021


M. stantonii   Maki & Looft 2018


Megasphaera paucivorans


Megasphaera vaginalis


" Colibacter massiliensis "  Mailhe et al. 2017


Megasphaera micronuciformis


Anaeroglobus geminatus


" Megasphaera hominis "


" Caecibacter massiliensis "  Ricaboni et al. 2017  (incl.  Megasphaera hexanoica )


M. hutchinsoni


M. lornae


M. cerevisiae


M. stantonii


M. elsdenii


M. massiliensis


Unassigned species:


This  Bacillota -related article is a  stub . You can help Wikipedia by  expanding it .


Mobiluncus  is a  genus  of  Gram-positive , [ 2 ]   anaerobic , rod-shaped  bacteria . These bacteria may be stained either Gram-negative or Gram-variable. However, they are classified as Gram-positive rods due to the fact that they possess a Gram-positive cell wall, lack endotoxin and are sensitive to vancomycin, erythromycin and ampicillin, but resistant to colistin. [ 3 ]


These organisms are found in the human  vagina , particularly in association with  Gardnerella vaginalis  in cases of  bacterial vaginosis . [ 4 ] [ 5 ]


Mycoplasma  is a genus of  bacteria  that, like the other members of the class  Mollicutes , lack a  cell wall , and its  peptidoglycan , around their  cell membrane . [ 1 ]  The absence of peptidoglycan makes them naturally resistant to antibiotics such as the  beta-lactam antibiotics  that target cell wall synthesis. They can be  parasitic  or  saprotrophic . Several species are  pathogenic  in humans, including  M. pneumoniae , which is an important cause of  "walking" pneumonia  and other respiratory disorders, and  M. genitalium , which is believed to be involved in  pelvic inflammatory diseases .  Mycoplasma  species (like the other species of the class  Mollicutes ) are among the smallest organisms yet discovered, [ 2 ]  can survive without oxygen, and come in various shapes. For example,  M. genitalium  is flask-shaped (about 300 x 600  nm ), while  M. pneumoniae  is more elongated (about 100 x 1000  nm ), many  Mycoplasma  species are  coccoid . Hundreds of  Mycoplasma  species infect animals. [ 3 ]


In casual speech, the name  "mycoplasma"  (plural  mycoplasmas  or  mycoplasms ) generally refers to all members of the  class Mollicutes . In formal scientific classification, the designation  Mycoplasma  refers exclusively to the genus, a member of the  Mycoplasmataceae , the only family in the  order Mycoplasmatales  (see "scientific classification").


The term "mycoplasma", from the Greek μύκης,  mykes  (fungus) and πλάσμα,  plasma  (formed), was first used by  Albert Bernhard Frank  in 1889 to describe an altered state of plant cell cytoplasm resulting from infiltration by fungus-like microorganisms. [ 4 ] [ 5 ]   Julian Nowak  later proposed the name mycoplasma for certain filamentous microorganisms imagined to have both cellular and acellular stages in their lifecycles, which could explain how they were visible with a microscope, but passed through filters impermeable to other bacteria. [ 6 ]  Later, the name for these mycoplasmas was  pleuropneumonia-like organisms  (PPLO), broadly referring to organisms similar in  colonial morphology  and filterability to the causative agent (a  Mycoplasma  species) of  contagious bovine pleuropneumonia . [ 7 ]  At present, all these organisms are classified as Mollicutes, and the term  Mycoplasma  solely refers to the genus. [ citation needed ]


Species of  Mycoplasma , other than those listed below, have been recovered from humans, but are assumed to have been contracted from a non-human host. The following species use humans as the primary host: [ citation needed ]


Over 100 species have been included in the genus  Mycoplasma , a member of the class  Mollicutes .  They are  parasites  or  commensals  of humans, animals, and plants. The genus  Mycoplasma  uses  vertebrate  and  arthropod  hosts. [ 9 ]  Dietary nitrogen availability has been shown to alter  codon bias  and genome evolution in  Mycoplasma  and the plant parasites  Phytoplasma . [ 10 ]


Mycoplasma  species are among the smallest free-living organisms (about 0.2 - 0.3 μm in diameter). [ 11 ] [ 12 ]  They have been found in the pleural cavities of cattle suffering from pleuropneumonia. These organisms are often called MLO (mycoplasma-like organisms) or, formerly, PPLO (pleuropneumonia-like organisms). [ 7 ]


Due to the lack of a rigid cell wall,  Mycoplasma  species (like all  Mollicutes )  can contort into a broad range of shapes, from round to oblong. They are  pleomorphic  and therefore cannot be identified as rods,  cocci  or  spirochetes . [ 13 ]


Colonies show the typical "fried egg" appearance (about 0.5 mm in diameter). [ 12 ]


In 1954, using phase-contrast microscopy, continual observations of live cells have shown that  Mycoplasma  species ("mycoplasmas", formerly called pleuropneumonia-like organisms, PPLO, now classified as  Mollicutes ) and  L-form bacteria  (previously also called L-phase bacteria) do not proliferate by binary fission, but by a uni- or multi-polar  budding  mechanism. Microphotograph series of growing microcultures of different strains of PPLOs, L-form bacteria and, as a control, a Micrococcus species (dividing by binary fission) have been presented. [ 12 ]   Additionally, electron microscopic studies have been performed. [ 14 ]


Previously, [ when? ]   Mycoplasma  species (often commonly called "mycoplasmas", now classified as  Mollicutes ) were sometimes considered stable  L-form bacteria  or even viruses, but  phylogenetic analysis  has identified them as bacteria that have lost their cell walls in the course of evolution. [ 15 ]


The medical and agricultural importance of members of the genus  Mycoplasma  and related genera have led to the extensive cataloging of many of these organisms by culture,  serology , and small sub-unit  rRNA  gene and whole-genome sequencing. A recent focus in the sub-discipline of  molecular phylogenetics  has both clarified and confused certain aspects of the organization of the class  Mollicutes . [ 16 ]


Originally, [ when? ]  the  trivial name  "mycoplasmas" commonly denoted all members of the class  Mollicutes  (from Latin  mollis  "soft" and  cutis  "skin"), which lack cell walls due to their genetic inability to synthesize  peptidoglycan .


Taxonomists  once [ when? ]  classified  Mycoplasma  and relatives in the phylum  Firmicutes , consisting of low G+C  Gram-positive bacteria  such as  Clostridium ,  Lactobacillus , and  Streptococcus ; but modern polyphasic analyses situate them in the phylum  Tenericutes . [ 17 ]


Historically, [ when? ]  the description of a bacterium lacking a cell wall was sufficient to classify it to the genus  Mycoplasma  and as such it is the oldest and largest genus of the class with about half of the class' species (107 validly described), each usually limited to a specific host and with many hosts harboring more than one species, some pathogenic and some commensal. In later studies, [ when? ]  many of these species were found to be phylogenetically distributed among at least three separate orders. A limiting criterion for inclusion within the genus  Mycoplasma  was [ when? ]  that the organism has a vertebrate host. [ citation needed ]


By the 1990s, it had become readily apparent that this approach was problematic: the  type species ,  M. mycoides , along with other significant mycoplasma species like  M. capricolum , is evolutionarily more closely related to the genus  Spiroplasma  in the order  Entomoplasmatales  than to the other members of the genus  Mycoplasma . As a result, if the group was to be rearranged to match phylogeny, a number of medically important species (e.g.  M. pneumoniae ,  M. genitalium ) would have to be put in a different genus, causing widespread confusion in medical and agricultural communities. The genus was discussed multiple times by the  International Committee on Systematic Bacteriology 's (ICSB) subcommittee on Mollicutes between 1992 and 2011, to no effect. [ 18 ]


Regardless of taxonomy, by 2007 it was solidly known that Molicutes could be divided into four nontaxonomic lineages. [ 19 ] [ 20 ]


In 2018, Gupta et al. re-circumscribed the genus  Mycoplasma  around  M. mycoides . A total of 78 species were removed from  Mycoplasma , creating five new genera and a number of higher taxonomic levels. Under this new scheme, a new family  Mycoplasmoidaceae  was created to correspond to the "pneumoniae" group, with  M. pneumoniae  and related species transferred to a new genus  Mycoplasmoides . Another new family  Metamycoplasmataceae  was created to correspond to the "hominis" group. Both families belong to a new order  Mycoplasmoitales , distinct from the  Mycoplasmatales  of  Mycoplasma . [ 20 ]  The taxonomy was accepted by the ICSB with validation list 184 in 2018 and became the  correct name . Both  List of Prokaryotic names with Standing in Nomenclature  (LPSN) [ 18 ]  and  National Center for Biotechnology Information  (NCBI) now use the new nomenclature. [ 21 ]


Gupta's proposed taxonomy, as expected, moved the medically important "pneumoniae" group out of  Mycoplasma  into its own genus. As a result, a number of mycoplasmologists petitioned to the ICSB to reject the name in 2019. They argue that although Gupta's phylogenetic methods were likely solid, the proposed name changes are too sweeping to be practically adopted, citing some principles of the Code such as "name stability". [ 22 ]  Gupta and Oren wrote a rebuttal in 2020, further detailing the pre-existing taxonomic problems. [ 23 ] [ 24 ]  In 2022, the ICSP's Judicial Opinion 122 ruled in favor of the name changes proposed by Gupta, meaning they remain valid under the  Prokaryotic Code [ 25 ]  (and for the purpose of the LPSN, they remain the " correct names "). [ 24 ]  However, the older names also remain valid; their use remains acceptable under the Code. [ 25 ]


Gupta  et al.  2019 performed some uncontroversial sorting of the order Mycoplasmatales. [ 26 ]


M. putrefaciens   Tully et al. 1974


M. cottewii   Da Massa et al. 1994


M. yeatsii   Da Massa et al. 1994


M. capri   (Edward 1953) Hudson, Cottew & Adler 1967 non El Nasri 1966


M. mycoides   (Borrel et al. 1910) Freundt 1955


M. capricolum   Tully et al. 1974


M.  capricolum capripneumoniae   Leach, Erno & MacOwan 1993


M. leachii   Manso-Silván et al. 2009


M. putrefaciens


M. cottewii


M. yeatsii


M. feriruminatoris   Fischer et al. 2015 [ 33 ]


M. capri


M. mycoides


M. capricolum


M. leachii


Mycoplasma  species are often found in research laboratories as contaminants in  cell culture . Mycoplasmal cell culture contamination occurs due to contamination from individuals or contaminated cell culture  medium  ingredients. [ 34 ]   Mycoplasma  cells are physically small – less than 1  μm, so are difficult to detect with a conventional  microscope . [ citation needed ]


Mycoplasmae may induce cellular changes, including  chromosome  aberrations, changes in  metabolism  and cell growth. Severe  Mycoplasma  infections may destroy a cell line. Detection techniques include  DNA probe ,  enzyme immunoassays ,  PCR , plating on sensitive  agar  and staining with a  DNA  stain including  DAPI  or  Hoechst . [ 35 ]


An estimated 11 to 15% of U.S. laboratory cell cultures are contaminated with mycoplasma.
A  Corning  study showed that half of U.S. scientists did not test for  Mycoplasma  contamination in their cell cultures. The study also stated that, in former Czechoslovakia, 100% of cell cultures that were not routinely tested were contaminated while only 2% of those routinely tested were contaminated (study p. 6). Since the U.S. contamination rate was based on a study of companies that routinely checked for  Mycoplasma , the actual contamination rate may be higher. European contamination rates are higher and that of other countries are higher still (up to 80% of Japanese cell cultures). [ 36 ]
About 1% of published  Gene Expression Omnibus  data may have been compromised. [ 37 ] [ 38 ]  Several antibiotic-containing formulations of antimycoplasmal reagents have been developed over the years. [ 39 ]


A chemically synthesized genome of a mycoplasmal cell based entirely on synthetic DNA which can self-replicate has been referred to as  Mycoplasma laboratorium . [ 40 ]


Several  Mycoplasma  species can  cause disease , including  M. pneumoniae , which is an important cause of  atypical pneumonia  (formerly known as "walking pneumonia"), and  M. genitalium , which has been associated with  pelvic inflammatory diseases . Mycoplasma infections in humans are associated with skin eruptions in 17% of cases. [ 41 ] : 293


The P1 antigen is the primary  virulence factor  of mycoplasma, specifically the Pneumoniae group. P1 is a membrane associated protein that allows adhesion to  epithelial cells . The P1 receptor is also expressed on  erythrocytes  which can lead to autoantibody  agglutination  from mycobacteria infection. [ 42 ]


Mycoplasma  and  Ureaplasma  species are not part of the normal  vaginal flora . Some Mollicutes species are spread through sexual contact. [ 43 ]  These species have a negative effect on fertility. [ 43 ]  Mollicutes species colonizing the human genital tract are: [ 43 ]


M. hominis  causes  male sterility /Genitals inflammation  in humans. [ citation needed ]


Mycoplasma  species have been isolated from women with  bacterial vaginosis . [ 3 ]   M. genitalium  is found in women with  pelvic inflammatory disease . [ 44 ]  In addition, infection is associated with increased risk of  cervicitis ,  infertility ,  preterm birth  and  spontaneous abortion . [ 45 ]   Mycoplasma genitalium  has developed resistance to some antibiotics. [ 46 ]


Low birth-weight, preterm infants are susceptible to  Mycoplasma  and  Ureaplasma  infections. [ 8 ]   Mycoplasma  species are associated with  infant respiratory distress syndrome ,  bronchopulmonary dysplasia , and  intraventricular hemorrhage  in preterm infants. [ 3 ]


Several species of  Mycoplasma  are frequently detected in different types of  cancer  cells. [ 47 ] [ 48 ] [ 49 ]  These species are:


The majority of these  Mycoplasma  species have shown a strong correlation to  malignant transformation  in mammalian cells  in vitro .


The presence of  Mycoplasma  was first reported in samples of cancer tissue in the 1960s. [ 49 ]  Since then, several studies tried to find and prove the connection between  Mycoplasma  and cancer, as well as how the bacterium might be involved in the formation of cancer. [ 48 ]  Several studies have shown that cells that are chronically infected with the bacteria go through a multistep transformation. The changes caused by chronic mycoplasmal infections occur gradually and are both  morphological  and  genetic . [ 48 ]  The first visual sign of infection is when the cells gradually shift from their normal form to sickle-shaped. They also become  hyperchromatic  due to an increase of DNA in the nucleus of the cells. In later stages, the cells lose the need for solid support to grow and proliferate, [ 56 ]  as well as the normal contact-dependent inhibition cells. [ 49 ]


Cells infected with  Mycoplasma  for an extended period of time show significant chromosomal abnormalities. These include the addition of chromosomes, the loss of entire chromosomes, partial loss of chromosomes, and  chromosomal translocation . All of these genetic abnormalities may contribute to the process of malignant transformation. Chromosomal translocation and extra chromosomes help create abnormally high activity of certain  proto-oncogenes , which caused by these genetic abnormalities and include those encoding  c-myc ,  HRAS , [ 50 ]  and  vav . [ 48 ]  The activity of proto-oncogenes is not the only cellular function that is affected; tumour suppressor genes are affected by the chromosomal changes induced by mycoplasma, as well. Partial or complete loss of chromosomes causes the loss of important genes involved in the regulation of cell proliferation. [ 49 ]  Two genes whose activities are markedly decreased during chronic infections with mycoplasma are the  Rb  and the  p53  tumour suppressor genes. [ 48 ]  Another possible mechanism of carcinogenesis is  RAC1  activation by a small GTPase-like protein fragment of Mycoplasma. [ 57 ]  A major feature that differentiates mycoplasmas from other carcinogenic pathogens is that the mycoplasmas do not cause the cellular changes by insertion of their own genetic material into the host cell. [ 50 ]  The exact mechanism by which the bacterium causes the changes is not yet known. [ citation needed ]


The malignant transformation induced by  Mycoplasma  species is also different from that caused by other pathogens in that the process is reversible. The state of reversal is, however, only possible up to a certain point during the infection. The window of time when reversibility is possible varies greatly; it depends primarily on the  Mycoplasma  involved. In the case of  M. fermentans , the transformation is reversible until around week 11 of infection and starts to become irreversible between weeks 11 and 18. [ 49 ]  If the bacteria are killed using  antibiotics [ 49 ]  (i.e.  ciprofloxacin [ 48 ]  or  Clarithromycin [ 58 ] ) before the irreversible stage, the infected cells should return to normal.


Epidemiologic, genetic, and molecular studies suggest infection and inflammation initiate certain cancers, including those of the prostate.  M. genitalium  and  M. hyorhinis  induce malignant phenotype in benign human prostate cells (BPH-1) that were not tumorigenic after 19 weeks of exposure.
 [ 53 ]


Colon cancer : In a study to understand the effects of  Mycoplasma  contamination on the quality of cultured human colon cancer cells, a positive correlation was found between the number of  M. hyorhinis  cells present in the sample and the percentage of CD133-positive cells (a glycoprotein with an unknown function). [ 59 ]


Gastric cancer : Strong evidence indicates the infection of  M. hyorhinis  contributes to the development of cancer within the stomach and increases the likelihood of malignant cancer cell development. [ 60 ]


Lung cancer : Studies on lung cancer have supported the belief that more than a coincidental positive correlation exists between the appearance of  Mycoplasma  strains in patients and the infection with tumorigenesis. [ 61 ]


Prostate cancer : p37, a protein encoded for by  M. hyorhinis , has been found to promote the invasiveness of prostate cancer cells. The protein also causes the growth, morphology, and gene expression of the cells to change, causing them to become a more aggressive phenotype. [ 62 ]


Renal cancer : Patients with renal cell carcinoma (RCC) exhibited a significantly high amount of Mycoplasma sp. compared with the healthy control group. This suggests  Mycoplasma  may play a role in the development of RCC. [ 58 ]


Mycoplasma hominis  is a species of bacteria in the genus  Mycoplasma .  M.   hominis  has the ability to penetrate the interior of human cells. [ 1 ]  Along with  ureaplasmas , mycoplasmas are the smallest free-living organisms known.


They have no cell wall and therefore do not  Gram stain . [ 2 ]


Mycoplasma hominis  is associated with  pelvic inflammatory disease [ 3 ] [ 4 ]  and  bacterial vaginosis . [ 5 ]  It is also associated with male infertility. [ 6 ]  This species causes  a sexually transmitted infection . [ 7 ]  It is susceptible to the antibiotic  clindamycin . [ 8 ]


Growth of "fried egg" colonies on glucose agar medium within 24–48 hours is a characteristic of  Mycoplasma hominis . [ citation needed ]


This pathogen may latently infect the  chorionic villi  tissues of pregnant women, thereby impacting pregnancy outcome. [ 9 ]


Mycoplasma hominis  is an opportunistic human mycoplasma species residing in the lower urogenital tract. [ 10 ]  It is a common human  urogenital  Mycoplasma species that lacks a cell wall. Due to the absence of the cell wall,  M. hominis  is innately resistant to β-lactams and to all antibiotics which target the cell wall. [ 11 ]  Additionally, it is the simplest self-replicating microorganism known. [ 12 ]   This reaps consequences such as a lack of detection by light microscopy, and complex nutritional requirements. [ 11 ]  Due to the fact that it does not have a cell wall,  Mycoplasma hominis  does not  gram stain [ 2 ]  although it is surprisingly often described as gram-negative.


The morphology is quite variable and seems to depend, in part, on the age of the culture as the smallest form observed, coming from the elementary body, is 80nm to 100nm wide in diameter. [ 13 ]  Different cell forms have been observed varying from coccoid cells to filaments and irregularly shaped structures with coccoid forms and ring- or disc-shaped cells reigning predominant. [ 14 ]  Coccal forms of the species are associated with binary fission while fragmentary filaments, and budding cells were also encountered.  This fact along with the fact that in different labs, the same strains grew at different rates, leads to the conclusion that cultural conditions have influenced the rate of division and cellular morphology in this species. [ 15 ]


The internal components of the much larger cells in the species are also variable. These cells can contain different structures such as ribosome-like granules, nuclear areas of netlike strands, dense cytoplasmic bodies and large vacuoles. These observations indicate multiple modes of reproduction for this organism. [ 13 ]


Analysis of the  M. hominis  PG21 genome sequence shows that this organism is the second smallest genome among self-replicating free living organisms. [ 10 ]  Due to their minimal genomes, M. hominis have reduced metabolic capabilities which are characterized by distinct energy-generating pathways. [ 10 ]  Three energy pathways that  M. hominis  is capable of going through is Embden-Meyerhoff-Parnas (EMP), arginine dihydrolase and Riboflavin metabolism. [ 10 ]


Mycoplasma hominis, a microorganism without a cell wall, is difficult to detect because it cannot be identified through Gram staining. [ 16 ]  Culturing it is demanding and time-consuming due to specialized requirements and while direct DNA testing is an option, it's not always highly sensitive, and not all labs possess its capabilities. [ 17 ]  This likely leads to underreporting of M. hominis infections, causing delayed diagnosis and less favorable treatment outcomes [ 18 ]  Cells of  M. hominis  prepared from batch cultures show uniform exponential growth and appear to divide through the process of binary fission with pleomorphic forms appearing upon further incubation. [ 19 ]  Similar behavior was demonstrated by another laboratory-adapted strain and by three other clinical isolates, making this seem characteristic of the species. [ 19 ]   M. hominis  grows in a variety of defined laboratory media, such as arginine broth and can also be cultivated in water. [ 20 ]  Growth in this species, as well as all species of mycoplasmas, is driven by anaerobic respiration. [ 21 ]


The primary sites of localization for M. hominis is the oropharynx and the genitourinary tract with positive pathogenicity. [ 22 ]  It is capable of infecting human beings as well as non-human primates. [ 23 ]


Mycoplasma hominis  is more than likely implicated in many different diseases, but its role is unclear for most of them. M. hominis is implicated in pelvic inflammatory disease, which may cause ectopic pregnancy. [ 23 ]  It prospers in the environment created by other gram negative bacteria implicated in bacterial vaginosis and may be a cause of preterm delivery and miscarriage. It is also implicated in postpartum fever, because it may be a cause of endometritis. M. hominis is also suspected to be the cause of neonatal infections such as conjunctivitis, respiratory distress, fever, meningitis, abscesses, and congenital pneumonia. [ 23 ]  In adults, M. hominis may be implicated in pharyngitis, septicaemia, lung infections, central nervous system infections, other respiratory tract infections, joint infection, and wound infections. M. hominis infections are usually not seen in healthy adults. [ 23 ]
Understanding how M. hominis contributes to infections in adult patients, particularly in areas outside the genital tract like the central nervous system (CNS), post-operative wound sites, the chest, and joints, has posed a challenge. [ 24 ]  Recent data shows an increase in reported post-operative CNS infections caused by Mycoplasma, likely due to the more extensive use of advanced diagnostic methods like PCR and DNA sequencing, especially when routine cultures fail to detect bacterial growth. [ 25 ]


The incubation period of  M. hominis  is unknown. [ citation needed ]


Many antibiotics kill bacteria by weakening the cell wall. However, mycoplasma bacteria lack this cellular structure causing some antibiotics, like penicillin, to be ineffective treatment options. [ 26 ]


Oral tetracyclines have historically been the drugs of choice for use against urogenital and systemic infections due to  M. hominis. [ 11 ]  In locations and patient populations where tetracycline resistance or treatment failures are common, other drugs such as fluoroquinolones should be considered guided by  in vitro  susceptibility data when possible. [ 11 ]


Recent epidemiologic studies demonstrate that 18% of  Mycoplasma hominis  are resistant to ciprofloxacin and 61% are resistant to azithromycin. Resistance to minocycline is 6%. [ 27 ]


Some infections may be treated by a single antibiotic. [ 11 ]  In other cases such as severe  M. hominis  infections occurring in immunocompromised patients, combination of drugs usually active against the mycoplasmas have been recommended. In those cases, guidelines for optimal therapy remain to be established. Current therapeutic considerations are based only upon case reports. [ 11 ]


The bacterium is often passed through sex, so to help keep this infection away, safe sex practices should be used. [ 26 ]


DNA sequence data is incomplete for  M. hominis .  M. hominis  uses an atypical type of energy metabolism, dependent upon the degradation of arginine. Other mycoplasmas lack this characteristic. Determining the genome will provide information that would facilitate the understanding of metabolic reconstitutions. [ 28 ]


Peptococcus  is a Gram-positive bacterium genus in the family  Peptococcaceae .


Species in the genus are part of the  human microbiome , especially in the bacteria that form the  gut flora . They are part of the flora of the mouth, upper respiratory tract and large intestine.


Mezlocillin  is an antibiotic that is effective against  Peptococcus  species.


Peptococcus niger  is the only species left in the genus. All others have been moved to  Peptostreptococcus . [ 1 ]


Peptoniphilus  is a genus of bacteria in the phylum  Bacillota  ( Bacteria ). [ 2 ]


The name  Peptoniphilus  derives from: Neo-Latin  noun  peptonum , peptone;  Neo-Latin  adjective  philus  from  Greek  adjective  philos (φίλος)  meaning friend, loving;  Neo-Latin   masculine gender  noun  Peptoniphilus , friend of peptone, referring to the use of peptone as a major energy source. [ 3 ]


Peptoniphilus are  gram positive   anaerobic   cocci  that were formerly classified in the genus  Peptostreptococcus . [ 4 ]  They are non-saccharolytic, use peptone as a major energy source and produce butyrate. [ 4 ]


This genus is part of the vaginal and gut microbiota. [ 5 ] [ 6 ]  They have been reported to as present in diabetic skin and soft tissue infections, bone and joint infections, surgical site infections, chorioamnionitis and bloodstream infections. [ 6 ]  They are typically found as part of polymicrobial infections but are difficult to recover with usual clinical cultures. They have been increasingly reported with the more widespread use of  16S   PCR  and  MALDI-TOF  for identification. [ 4 ]  They are noted to be linked with an impairment of wound-healing in patients with diabetic foot ulcers if present in abundance during the initial infection.  [ 7 ]


The genus contains 17 species (including basonyms and synonyms), namely [ 3 ]


Peptostreptococcus anaerobius
 Peptostreptococcus canis
 Peptostreptococcus porci
 Peptostreptococcus russellii
 Peptostreptococcus stomatis


Peptostreptococcus  is a  genus  of  anaerobic ,  Gram-positive , non- spore  forming  bacteria . The  cells  are small,  spherical , and can occur in short chains, in pairs or individually. They typically move using cilia. [ 2 ]   Peptostreptococcus  are slow-growing bacteria with increasing resistance to  antimicrobial  drugs. [ 3 ]   Peptostreptococcus  is a normal  inhabitant  of the healthy lower reproductive tract of women. [ 4 ] [ 5 ]


Peptostreptococcus  species are  commensal  organisms in humans, living predominantly in the mouth, skin,  gastrointestinal , vagina and  urinary tracts , and are members of the  gut microbiota . Under  immunosuppressed  or  traumatic  conditions these organisms can become  pathogenic , as well as  septicemic , harming their host.  Peptostreptococcus  can cause brain, liver, breast, and lung  abscesses , as well as generalized  necrotizing  soft tissue  infections . They participate in mixed  anaerobic infections , a term which is used to describe infections that are caused by multiple bacteria that do not require or may even be harmed by oxygen. [ 6 ]


Peptostreptococcus  species are susceptible to  beta-lactam antibiotics . [ 7 ]


They are isolated with high frequency from all specimen sources. Anaerobic gram-positive cocci such as  Peptostreptococcus  are the second most frequently recovered anaerobes and account for approximately one quarter of anaerobic isolates found. Most often anaerobic gram-positive cocci are usually recovered mixed in with other anaerobic or aerobic bacteria from various infections at different sites of the human body. This contributes to the difficulty of isolating  Peptostreptococcus  organisms. [ 8 ]


Peptostreptococcus  species that are found in clinical infections were once part of the genus formerly known as  Peptococcus .  Peptostreptococcus  is the only genus among anaerobic gram-positive cocci that is encountered in clinical infections. As such,  Peptostreptococcus  species are viewed as being clinically significant anaerobic cocci. Other similar clinically significant anaerobic cocci include  Veillonella  species (gram-negative cocci), and microaerophilic streptococci (aerotolerant). Anaerobic gram-positive cocci include various clinically significant species of the genus  Peptostreptococcus . [ 9 ]


The species of anaerobic gram-positive cocci isolated most commonly include  Peptostreptococcus magnus ,  Peptostreptococcus asaccharolyticus ,  Peptostreptococcus anaerobius ,  Peptostreptococcus prevotii , and  Peptostreptococcus micros . [ citation needed ]


Anaerobic gram-positive cocci that produce large amounts of lactic acid during the process of carbohydrate fermentation were reclassified as  Streptococcus parvulus  and  Streptococcus morbillorum  from  Peptococcus  or  Peptostreptococcus . Most of these organisms are anaerobic, but some are microaerophilic. [ citation needed ]


Due to a large amount of new research done on the human microbe and more information on bacteria, many species of bacteria have been renamed and re-classified.  Based on DNA homology and whole-cell polypeptide-pattern study findings supported by phenotypic characteristics, the DNA homology group of  microaerobic  streptococci that was formerly known as  Streptococcus anginosus  or  Streptococcus milleri  is now composed of three distinct species:  S. anginosus ,  S. constellatus , and  S. intermedius . The microaerobic species  S. morbillorum  was transferred into the genus  Gemella . A new species within the genus  Peptostreptococcus  is  Peptostreptococcus hydrogenalis ; it contains the indole-positive, saccharolytic strains of the genus. [ 10 ]


Peptostreptococcus  infections occur in/on all body sites, including the CNS, head, neck, chest, abdomen, pelvis, skin, bone, joint, and soft tissues. Adequate therapy must be taken against infections, or it could result in clinical failures.
Peptostreptoccocci are often overlooked and they are very difficult to isolate, appropriate specimen collection is required. Peptostreptococci grow slowly which makes them increasingly resistant to antimicrobrials. [ 9 ]


The most common  Peptostreptococcus  species found in infections are  P. magnus  (18% of all anaerobic gram-positive cocci and microaerophilic streptococci),  P. asaccharolyticus  (17%),  P. anaerobius  (16%),  P. prevotii  (13%),  P. micros  (4%),  P. saccharolyticus  (3%), and  P. intermedius  (2%). [ 11 ]


P. magnus  were highly recovered in bone and chest infections.  P. asaccharolyticus  and  P. anaerobius  had the highest recovery rate in obstetrical/gynecological and respiratory tract infections and wounds.  When anaerobic and facultative cocci were recovered most of the infection were polymicrobial. Most patients from whom microaerophilic streptococci were recovered in  pure culture  had abscesses (e.g., dental, intracranial, pulmonary), bacteremia, meningitis, or conjunctivitis.  P. magnus  is the most commonly isolated anaerobic cocci and is often recovered in pure culture. Other common Peptostreptococci in the different infectious sites are  P. anaerobius  which occurs in oral infections;  P. micros  in respiratory tract infections,  P. magnus ,  P. micros ,  P. asaccharolyticus ,  P. vaginalis , and  P. anaerobius  in skin and soft tissue infections;  P. magnus  and  P. micros  in deep organ abscesses;  P. magnus ,  P. micros , and  P. anaerobius  in gastrointestinal tract-associated infections;  P. magnus ,  P. micros ,  P. asaccharolyticus ,  P. vaginalis ,  P. tetradius , and  P. anaerobius  in female genitourinary infections; and  P. magnus ,  P. asaccharolyticus ,  P. vaginalis , and  P. anaerobius  in bone and joint infections and leg and foot ulcers. [ 12 ]


Many infections caused by  Peptostreptococcus  bacteria are synergistic. Bacterial synergy, the presence of which is determined by mutual induction of sepsis enhancement, increased mortality, increased abscess inducement, and enhancement of the growth of the bacterial components in mixed infections, is found between anaerobic gram-positive cocci and their aerobic and anaerobic counterparts. The ability of anaerobic gram-positive cocci and microaerophilic streptococci to produce capsular material is an important virulence mechanism, but other factors may also influence the interaction of these organisms in mixed infections. [ 13 ]


Although anaerobic cocci can be isolated from infections at all body sites, a predisposition for certain sites has been observed. In general,  Peptostreptococcus  species, particularly  P. magnus , have been recovered more often from subcutaneous and soft tissue abscesses and diabetes-related foot ulcers than from intra-abdominal infections.  Peptostreptococcus  infections occur more often in chronic infections. [ 9 ]


It is difficult to determine the exact frequency of  Peptostreptococcus  infections because of inappropriate collection methods, transportation, and specimen cultivation.  Peptostreptococcus  infections are most commonly found in patients who have had or have chronic infections. Patients who have predisposing conditions are shown to have 5% higher recovery rate of the bacteria in blood cultures. [ 14 ]


Of all anaerobic bacteria recovered at hospitals from 1973 to 1985, anaerobic gram-positive cocci accounted for 26% of it. The infected sited where these organisms were found in the greatest abundance were obstetrical and gynecological sites (35%), bones (39%) cysts (40%), and ears (53%). Occasionally found in other places such as abdomen,  lymph nodes , bile, and eyes. [ 14 ]


Frequency of infections is greater in developing countries because treatment is often slow, or it is impossible to get the adequate treatment, but mortality due to  Peptostreptococcus  infections have decreased in the last 30 years and will continue to do so due to better treatment. [ citation needed ]


All ages are susceptible to  Peptostreptococcus  infections, however children are more likely to get head and neck infections. [ citation needed ]


Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered in polymicrobial skin and soft tissue infections, such as gangrene, fasciitis, ulcers, diabetes-related foot infections, burns, human or animal bites, infected cysts, abscesses of the breast, rectum, and anus. Anaerobic gram-positive cocci and microaerophilic streptococci are generally found mixed with other aerobic and anaerobic bacteria that originate from the mucosal surface adjacent to the infected site or that have been inoculated into the infected site. [ citation needed ]


Peptostreptococcus  spp. can cause infections such as gluteal decubitus ulcers, diabetes-related foot infections, and rectal abscesses.
Anaerobic gram-positive cocci and microaerophilic streptococci are part of the normal skin microbiota, so it is hard to avoid contamination by these bacteria when obtaining specimens. [ 8 ] [ 9 ]


CNS infections can be isolated from  subdural empyema  and brain abscesses which are a result of chronic infections. Also isolated from sinuses, teeth and mastoid. 46% of 39 brain abscesses in one study showed anaerobic gram-positive cocci and microaerophilic streptococci. [ 8 ] [ 9 ]


There is a high rate of anaerobic cocci colonization which accounts for the organisms significance in these infections. Anaerboci gram-positive cocci and micraerophilic streptococci are often recovered in these infections.  They have been recovered in 15% of patients with chronic mastoiditis. When Peptostreptococci and other anaerobes predominate, aggressive treatment of acute infection can prevent chronic infection. When the risk of anaerobic infection is high, as with intra-abdominal and post-surgical infections, proper antimicrobial prophylaxis may reduce the risk
90% of the time, other organisms were mixed in with the anaerobic gram-positive cocci and microaerophilic streptococci. This includes  Streptococcus  species, and  Staphylococcus aureus . [ 8 ] [ 9 ]   Peptostreptococcus micros  has a moderate association with periodontal disease. [ citation needed ]


Peptostreptococci can cause fatal endocarditis, paravalvular abscess, and  pericarditis . The most frequent source of bacteremia due to  Peptostreptococcus  are infections of the  oropharynx , lower respiratory tract, female genital tract, abdomen, skin, and soft tissues. Recent gynecological surgery,  immunosuppression , dental procedures, infections of the female genital tract, abdominal and soft tissue along with gastrointestinal surgery are predisposing factors for bacteremia due to  peptostreptococcus . [ citation needed ]


Microaerophilic streptococci typically account for 5-10% of cases of endocarditis; however, Peptostreptococci have only rarely been isolated. [ 8 ] [ 9 ]


Anaerobic gram-positive cocci and microaerophilic streptococci are most frequently found in aspiration pneumonia, empyema, lung abscesses, and  mediastinitis . These bacteria account for 10-20% of anaerobic isolated recovered from pulmonary infections.
It is difficult to obtain appropriate culture specimens. It requires a direct lung puncture, or the use of trans-tracheal aspiration. [ 8 ] [ 9 ]


Anaerobic gram-positive cocci are part of the normal gastrointestinal microbiota. They are isolated in approximately 20% of specimens from intra-abdominal infections, such as peritonitis. Found in abscesses of the liver, spleen, and abdomen. Like in upper respiratory tract and dental infections, anaerobic gram-positive cocci are recovered mixed with other bacteria. In this case they are mixed with organisms of intestinal origin such as E coli, bacteroides fragilis group, and clostridium species. [ 8 ] [ 9 ]


Anaerobic gram-positive cocci are frequently isolated from anaerobically infected bones and joints., they accounted for 40% of anaerobic isolates of osteomyelitis caused by anaerobic bacteria and 20% of anaerobic isolates of arthritis caused by anaerobic bacteria.  P magnus and P prevotii are the predominant bone and joint isolates. Management of these infections requires prolonged courses of antimicrobials and is enhanced by removal of the foreign material. [ 8 ] [ 9 ]


Peptostreptococcus  species are part of the  microbiota of the lower reproductive tract of women . [ 4 ] [ 5 ]


Infections with anaerobic gram-positive cocci and microaerophilic streptococci are often caused by: [ citation needed ]


When  Peptostreptococci  and other anaerobes predominate, aggressive treatment of acute infection can prevent chronic infection. When the risk of anaerobic infection is high, as with intra-abdominal and post-surgical infections, proper antimicrobial prophylaxis may reduce the risk.
Therapy with antimicrobials (e.g.,  aminoglycosides ,  trimethoprim-sulfamethoxazole , older  quinolones ) often does not eradicate anaerobes. [ citation needed ]


As of 2022, there are 5 species validly published in the genus  Peptostreptococcus , with several species formerly being described, that have been moved to a more accurate genus.


"Streptococcus anaerobius"


Peptostreptococcus anaerobius  is a species of bacteria belonging to the  Peptostreptococcus   genus  of  anaerobic ,  Gram-positive , non- spore  forming  bacteria . The  cells  are small,  spherical , and can occur in short chains, in pairs or individually. [ 2 ]   Peptostreptococcus  are slow-growing bacteria sometimes resistance to  antimicrobial  drugs. [ 3 ]   P. anaerobius  is intrinsically resistant to sodium polyethanol sulfonate (SPS), a component found  in many types of blood culture media.  [ 4 ]


Peptostreptococcus anaerobius  is present as part of the  microbiota of the lower reproductive tract of women  and has been recovered from women with  pelvic inflammatory disease  and  bacterial vaginosis . [ 5 ] [ 6 ]


Porphyromonas gingivalis  belongs to the  phylum   Bacteroidota  and is a  nonmotile ,  Gram-negative , rod-shaped,  anaerobic ,  pathogenic   bacterium . It forms black colonies on  blood agar .


It is found in the oral cavity, where it is implicated in  periodontal disease , [ 1 ]  as well as in the upper  gastrointestinal tract , the  respiratory tract , and the  colon . It has been isolated from women with  bacterial vaginosis . [ 2 ]


Collagen  degradation observed in chronic periodontal disease results in part from the  collagenase  enzymes of this  species . It has been shown in an  in vitro  study that  P. gingivalis  can invade  human   gingival   fibroblasts  and can survive in the presence of  antibiotics . [ 3 ]   P. gingivalis  invades gingival  epithelial   cells  in high numbers, in which case both bacteria and epithelial cells survive for extended periods of time. High levels of specific antibodies can be detected in patients harboring  P. gingivalis .


P. gingivalis  infection has been linked to  Alzheimer's disease [ 4 ]  and  rheumatoid arthritis . It contains the enzyme  peptidyl-arginine deiminase , which is involved in  citrullination . [ 5 ]  Patients with  rheumatoid arthritis  have increased incidence of periodontal disease; [ 6 ]  antibodies against the bacterium are significantly more common in these patients. [ 7 ]


P. gingivalis  is divided into K- serotypes  based upon  capsular   antigenicity  of the various types. [ 8 ]


The genome of  P. gingivalis  was described in 2003 revealing 1,990  open reading frames  (i.e. protein-coding sequences), encoded by 2,343,479 bp, with an average G+C content of 48.3%. [ 9 ]  An estimated 463 genes are  essential . [ 10 ]


Arg-gingipain (Rgp) and lys-gingipain (Kgp) are  endopeptidase  enzymes secreted by  P. gingivalis.  These  gingipains  serve many functions for the organism, contributing to its survival and virulence. [ 11 ]


Arg-gingipains have been found to play a key role in the collection of nutrients for  P. gingivalis  survival. Rgp degrades large peptides of the host organism to provide the bacterium with an abundant nitrogen and carbon source from human serum albumin. [ 12 ]   P. gingivalis  can also degrade  transferrin  within host cells which provides the organism with an abundant iron source needed to perform multiple cellular functions. [ 13 ]


The gingipains are also responsible for a number of necessary functions related to host invasion and colonization. Rgp gingipains are necessary for adhesion and invasion as they processed precursor proteins of long fimbriae. [ 13 ]  The  P. gingivalis  genes encoding RgpA, Kgp, and hemagglutinin A (HagA) were strongly expressed after incubation with  T. denticola . The hemagglutinin adhesion domain-containing proteins act to increase adhesive capacities of  P. gingivalis  with other bacterial species. [ 14 ]  They are also associated with coordinating the integrity of the biofilm in the developing and maturation phase. [ 15 ]  Lys- gingipains (Kgp) can bind to immobilized matrix proteins  fibrinogen  and  fibronectin  and may have a role in host colonization. [ 16 ]


Gingipains also have the ability to degrade multiple signals of the host immune response. They have the ability to cleave subclass 1 and 3  IgG antibodies [ 17 ]  as well as proinflammatory  cytokines  such as IL-1β, IL-2, IL-6, TNF-α and IL-8 in regions of high  P. gingivalis  concentration, [ 18 ]  impairing host immune response function. Rgp can inhibit IL-2 accumulation in  T-cells , which enables it to evade the host adaptive immune response, by modulating T-cell communication and proliferation. [ 19 ]


Gingipains are key factors in tissue damage symptoms of  periodontitis , which results from the degradation of  matrix metalloproteins ,  collagen , and  fibronectin . [ 13 ]  Degradation of these substrates interferes with interactions between host cells and the  extracellular matrix , therefore impeding wound healing and causing destruction of periodontal tissues. [ 13 ]  Rgp is responsible for eliciting the host inflammatory response via the p38α  MAPK  transduction pathway. This response likely contributes to the inflammatory nature of periodontitis and is involved in tissue and bone destruction. [ 12 ]


Gingipains have been associated with  Alzheimer's disease  (AD). Gingipains were discovered from  TMAs  of patients exhibiting AD brain pathology. Both RgpB and Kgp were discovered from  hippocampus  and  cerebral cortex  of AD patients and were found to be associated with  tau  load, a marker for AD pathology and  ubiquitin , which accumulates in tau tangles and  amyloid beta  plaques in AD brain.  P. gingivalis  16S rRNA was also discovered in the cerebral cortex and  csf  of AD brains. Pretreatment with gingipain inhibitors protected neuron cell degradation caused by administration of gingipains in murine model. [ 4 ]


The encapsulated strain of  P. gingivalis  is much more virulent than the nonencapsulated strain in a mouse abscess model. [ 20 ]  The capsule is a capsular polysaccharide and when present down regulates  cytokine  production especially proinflammatory  cytokines  IL-1β, IL-6, IL-8, and  TNF-α , indicating host evasion responses. [ 18 ] [ 20 ]  However, other studies have found the capsular polysaccharide to elicit host immune responses like  neutrophil  migration and dose and time dependent expression of cell migration  chemokines  like MCP-1, KC, MIP-2 and RANTES in capsular polysaccharide-challenged murine peritoneal macrophages. These conditions are likely to contribute to the inflammatory lesions observed in  periodontitis . [ 21 ]


Vaccines made from capsular polysaccharide of  P. gingivalis  apparently impair oral bone loss in murine models. These vaccines have been able to elicit potent immune responses such as increased  IgM  and  IgG  responses that recognize whole  P. gingivalis  organisms. [ 22 ]


Fimbriae  are appendages involved in cellular attachment and greatly contribute to virulence and are found on many Gram-negative and some Gram-positive bacteria. [ citation needed ]


P. gingivalis  virulence is heavily associated with fimbriae as they have been characterized to be key factors in adhesion, invasion, and colonization. Fimbriae are also responsible for invasion of membrane vesicles into host cells. [ 13 ]  They were found to bind to cellular α5β1  integrins , which mediated adherence and impaired the homeostatic controls of host cells. [ 23 ]  Fimbriae were also found to be associated with modulating β2 integrin adhesive activity for uptake by  monocytes  using the  CD14 / TLR2 / PI3K  signaling complex, which may contribute to intracellular evasion tactics by  P. gingivalis . [ 24 ]   P. gingivalis  has long fimbriae, short fimbriae, and accessory components, each of which have distinct functions. [ 15 ]


Long fimbriae (FimA), also known as major fimbriae, are long, peritrichous, filamentous components. [ 25 ]  They have a role in initial attachment and organization of biofilms, as they act as adhesins that mediate invasion and colonization of host cells contributing to  P. gingivalis  virulence. [ 15 ]


Short fimbriae (Mfa1), also known as minor fimbriae, have distinct roles from long fimbriae and are characterized to be essential for cell-cell auto aggregation and recruitment for  microcolony  formation. [ 25 ]  Short fimbriae are involved in cell-cell adhesion with other dental commensals. It was found to coadhere and develop biofilm in conjunction with  Streptococcus gordonii  by interaction with SspB streptococcal surface polypeptide. [ 26 ]  This interaction may be essential in the invasion of dentinal tubules by  P. gingivalis . [ 27 ]


Fim C, D, and E accessory components associate with the main FimA protein and have a role in binding with matrix proteins and interaction with CXC-chemokine receptor 4. Loss of function experiments have confirmed that  P. gingivalis  mutants deficient for Fim C, D, or E have drastically attenuated virulence. [ 28 ]


P. gingivalis  has many ways of evading host immune responses which affects its virulence. It does this by using a combination of gingipain proteases, a capsular polysaccharide, induction of host cell proliferation, and the cleavage of chemokines responsible for neutrophil recruitment. [ 17 ] [ 29 ]