Susceptibility of anaerobic bacteria to Sch 34343 and other -lactam antibiotics

The in-vitro activity of Sch 34343 was evaluated against 381 anaerobic clinical isolates and compared with that of imipenem, cefoxitin, latamoxef (moxalactam), cefotaxime and cefoperazone. Test isolates included strains with unknown resistance to the beta-lactam drugs, and two Bacteroides fragilis strains that could inactivate cefoxitin. Sch 34343 and imipenem demonstrated superior activity against all the anaerobic bacteria tested, with MIC90s less than or equal to 1 mg/l. Sch 34343 was generally one- to two-fold more active than imipenem. Resistance to both was demonstrated by the two Bact. fragilis strains that inactivated cefoxitin and by one strain of Fusobacterium; these three strains were also resistant to the other drugs studied. There were no other resistant strains to either Sch 34343 or imipenem. Cefotaxime and cefoperazone were the least active against the Bact. fragilis group, with resistance rates of 33 and 47%, respectively. Strains resistant to cefoxitin, latamoxef, cefotaxime and cefoperazone were found among some Clostridium spp. The Gram-positive cocci and Gram-positive bacilli were sensitive to all the drugs evaluated.