Instruct: Classify Amazon reviews into positive or negative sentiment
Query: May encourage bacterial growth

This brush is much too stiff and abrasive for use with reusable plastic drinking straws. The bristles are abrasive enough to cut into the plastic leaving indentations for bacteria and molds to establish and grow. My guess is that the need for a brush was recognized and someone in marketing or product development sourced a good deal on an industrial grade (inappropriate) brush. Please let me know (through comments) if you find a better brush. I haven't found one yet on Amazon (or elsewhere for that matter). Thanks.