Trends in antimicrobial susceptibility of the Streptococcus milleri group.

A collection of 114 clinical Streptococcus milleri group (SMG) strains at the Ryukyu University Hospital obtained in 1999 and 2000, was identified and tested for susceptibility to 12 antibiotics. The percentage of strains with intermediate susceptibility to penicillin G was relatively high (14%). Cefaclor and cefotiam, with a MIC 90 of 2 microg/ml, were less active than cefotaxime. Strains nonsusceptible to erythromycin, clindamycin, and azithromycin were found with a frequency of 8%, 5%, and 4%, respectively. Almost all of the SMG strains were susceptible to fluoroquinolones (except for 1% of the strains nonsusceptible to levofloxacin), and sitafloxacin (DU-6859a) was the most active agent among the 12 tested antibiotics.