Antimicrobial susceptibilities of Peptostreptococcus anaerobius and the newly described Peptostreptococcus stomatis isolated from various human sources.

Peptostreptococcus anaerobius sensu lato, currently including two closely related species, P. anaerobius and P. stomatis, is known to be more resistant than other gram-positive anaerobic cocci. We reidentified potential Peptostreptococcus isolates and tested their susceptibilities to eight antimicrobials. Notably, P. anaerobius had constantly higher values for the MIC at which 50% of the isolates are inhibited (MIC(50)) and the MIC(90) than P. stomatis.