Sch 34343, in-vitro antibacterial activity and beta-lactamase stability

The in-vitro activity of Sch 34343, a derivative of Sch 29482, was assessed and compared with that of other beta-lactam antibiotics. Nearly all Enterobacteriaceae, including ampicillin-resistant strains (MIC greater than or equal to 256 mg/l) were inhibited at concentrations ranging from 0.125-8 mg/l. The geometric mean MIC values varied from 0.25 mg/l to 2.4 mg/l for Klebsiella and Serratia spp., respectively. Sch 34343 did not inhibit Pseudomonas aeruginosa. The antibacterial activity was minimally altered by changes of medium or inoculum size. The results suggest high stability against plasmid- and chromosomally-mediated beta-lactamases. However, crude extracts of four Pseudomonas strains did hydrolyse Sch 34343. In addition to the high antibacterial activity and the beta-lactamase stability, Sch 34343 markedly inhibited most plasmid- and chromosomally-mediated beta-lactamases, with the exception of PSE-1 and PSE-4.