Antibacterial activity of an oral penem, Sch 29482

The in-vitro activity of Sch 29482 (SCH) was determined against 500 isolates and compared with that of older β -lactams, new parenteral β -lactamase-stable agents, aminoglycosides, and combination of trimethoprirn and suiphamethoxazole. The compound inhibited 90% of Streptococcus pyogenes, Str. agalactiae and Sir. pnewnoniae at 0.2mg/l. It was as active as cephalexin, cefotaxime and ampicillin and more active than moxalactam against Gram-positive species. SCH had MIC 90 values of 3.1 mg/l against Staphylococcus aureus . It did not inhibit methicillin-resistant Staph. aureus nor Staph. epidermidis. It inhibited β -lactamase-producing Haemophilus and Neisseria gonorrhoeae . The MIC 90 for Kiebsiella was 0.8 mg/l; MIC 90 for Citrobacter was 0.4 mg/l. Most Enterobacter were inhibited by 1.6 mg/l, similar to the concentrations of the aminothiazolyl cephalosporins and moxalactam. MICs of Serratia ranged from 1.6 to 25 mg/l comparable to ceftizoxime. Morganella and Providencia resistant to carbenicillin and gentamicin were inhibited. Of the Acinetobacier , 84% were inhibited, and it was more active than other agents. It did not inhibit Pseudomonas aeruginosa . Activity was minimally altered by changes in pH, type of medium, inoculum size, but was altered by serum. MIC—MBC differences were minor. SCH showed no synergy with aminoglycosides when tested against enterococci and Pseudomonas . It was not destroyed by common plasmid and chromosomal β -lactamases and it inhibited chromosomal β -Iactamases.