Duerden, “Antibiotic susceptibilities of Gram-positive anaerobic cocci: results of a sentinel study in England and Wales

Objective: A sentinel study was carried out to determine the antimicrobial susceptibilities of Gram-positive anaerobic cocci (GPAC) freshly isolated from clinical material in diagnostic laboratories in England and Wales. Methods: A total of 113 GPAC isolates consisting predominantly of current or former members of the genus Peptostreptococcus was obtained from 17 sentinel laboratories in England and one in Wales. Minimum inhibitory concentrations (MICs) of 10 antimicrobial agents were determined by the Etest method. The agents tested were: penicillin, tetracycline, erythromycin, cefoxitin, clindamycin, chloramphenicol, imi-penem, co-amoxiclav, piperacillin/tazobactam and metronidazole. MIC50 and MIC90 values for each drug-species combination were calculated whenever suitable numbers of each species were obtained. Results: Excellent spectra of activity (0 % resistance) against GPAC were seen for metronidazole, piperacillin/ tazobactam, cefoxitin, imipenem and chloramphenicol. Low degrees of resistance to co-amoxiclav (3.5%), clindamycin (7.1%), penicillin (7.1%) and significant degrees of resistance to tetracycline (41.6%) and erythromycin (27.4%) were detected. Some examples of putative macrolide-lincosamide linked resistance were noted in seven (6.2%) isolates of GPAC. Conclusion: This study is one of the largest susceptibility studies specifically on GPAC carried out to dat