Comparative activity of eighteen antimicrobial agents against anaerobic bacteria isolated in South Africa.

The in vitro activity of 18 antimicrobial agents was determined against 378 anaerobic bacteria isolated in Bloemfontein, South Africa, during 1996/97. Against the gram-positive isolates, MICs of penicillin and cefoxitin were >0.5 microg/ml and >16 microg/ml, respectively, for five and three strains of non-perfringens Clostridium spp. Seventeen Peptostreptococcus anaerobius strains were resistant to penicillin (MIC > or = 2 microg/ml). All gram-positive anaerobes tested except one Peptostreptococcus sp. and one Clostridium sp. were susceptible to dalfopristin-quinupristin (MICs < or = 1 microg/ml). The carbapenems exhibited excellent activity against the gram-positive isolates and were effective against most gram-negative anaerobes, with the exception of the fusobacteria. Only seven strains exhibited decreased susceptibility to trovafloxacin (MICs > 2 microg/ml). In mixed anaerobic/aerobic infections, carbapenems and the fourth-generation quinolone trovafloxacin were the agents most suitable for us as broad-spectrum monotherapy.