In-vitro activity and beta-lactamase stability and inhibitory properties of a new penem antibiotic, Sch 34343.

Sch 34343 is a new penem antibiotic. Its in-vitro activity was determined against Gram-positive and -negative aerobic and anaerobic isolates. Sch 34343 inhibited 90% of strains of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella spp, Citrobacter spp. and Shigella spp. at less than 1 mg/1. Ninety per cent of strains of Enterobacter, Morganella and Providencia spp. were inhibited by less than 4 mg/1. Sch 34343 did not inhibit Pseudomonas spp., and it had slightly less activity against Enterobacteriaceae than did cefotaxime or latamoxef (moxalactam), but it inhibited organisms resistant to cefoxitin, cefoperazone and piperacillin. Sch 34343 inhibited methicillin-susceptible Staphylococcus aureus at less than or equal to 0.25 mg/1, and it inhibited haemolytic streptococci at less than or equal to 0.06 mg/1. Sch 34343 inhibited Bacteroides fragilis at 0.06 mg/1, including some cefoxitin-resistant isolates. Sch 34343 was not hydrolysed by plasmid- or chromosomally-mediated beta-lactamases, was an excellent inhibitor of Richmond-Sykes type Ia beta-lactamases, and also inhibited, although less effectively, the common plasmid beta-lactamases. It induced beta-lactamases, but inhibited Enterobacter and Citrobacter spp. in which it induced beta-lactamase activity.