In-vitro antibiotic susceptibility and molecular analysis of anaerobic bacteria isolated in Cape Town, South Africa.

One hundred and twenty-three anaerobic isolates from Cape Town, South Africa, were tested in vitro against cefoxitin, chloramphenicol, metronidazole, co-amoxiclav, benzylpenicillin and clindamycin. Forty-five Gram-positive organisms were tested against RP59500 (a streptogramin). Resistance in the Gram-positive isolates was as follows: of the Clostridium perfringens isolates, 4% were resistant to benzylpenicillin and 4% to clindamycin; of the Peptostreptococcus anaerobius isolates, 10% were resistant to benzylpenicillin, 10% to cefoxitin and 10% to metronidazole; of the isolates of Peptostreptococcus spp., 12% were resistant to benzylpenicillin, 6% to metronidazole, 6% to chloramphenicol and 12% to RP59500. Of the Gram-negative organisms, those in the Bacteroides fragilis group were resistant to benzylpenicillin (83%), cefoxitin (5%), clindamycin (5%) and co-amoxiclav (2%). One clindamycin-resistant B. fragilis isolate carried a plasmid homologous to the ermF erythromycin resistance determinant.