two hypervirulent K2 ST86 strains were more virulent than those of K1 ST23 strains ([@B1]). Actually, in 1991, the first ST86 strain-CG43 causing severe bacteremia and PLA was reported in Taiwan ([@B11]). Recently, two hypervirulent K2 ST86 strains have been reported including strain hvKP1 isolated from a 24-year-old Vietnamese male in New York, which caused a unique PLA accompanied by a metastatic spread to the spleen ([@B10]), while another strain, isolated in South Korea, caused severe bacteraemic infection ([@B3]). Currently, ST86 isolated from five PLA cases throughout Taiwan, Hong Kong, and Singapore have been reported ([@B7]). Here, this is the first report of hvKP ST86 strains causing one suspected and two confirmed fatal cases in one surgery ward in China.

Discussion
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So far, compared to major ST23 of K1, not much has been studies about ST86 strains. In the present study, we have experimentally confirmed the presence of the pivotal VFs closely associated with PLA or hypermucoviscosity phenotype. In the present study, the more distinct difference of the ST86 strains than other K2 strains is the additional presence of *kfu* gene exclusively in our strains. To date, most reported ST86 strains have possessed a HV, *rmpA*, and PLA phenotype but no *kfu*. For example, two recently published studies described that all of the seven hvKP ST86 strains from France, USA, and Taiwan and 11 ST86 strains from Hong Kong, Singapore, and Taiwan, harbored no *kfu* gene ([@B12]; [@B7]). However, the two *Kp523/562* strains exhibited HV and unique K2-Aerobactin*-kfu-rmpA* positive phenotypes, yet no PLA. This may be associated with the rapid, acute onset of disease caused by hypervirulence of ST86 strains; the patients were dead before PLA occurred. Furthermore, the HV-Aerobactin-*rmpA* positive strains of *K. pneumoniae* had previously been shown to be highly lethal to mice and were more virulent than HV-Aerobactin-*rmpA* negative strains ([@B13]). It was well-known that the K1 PLA strains carried *kfu* gene inv