In vitro antibacterial activity and susceptibility of the cephalosporin Ro 13-9904 to beta-lactamases.

The in vitro activity of Ro 13-9904 was assessed against clinical isolated of common bacteria. Its activity against most enterobacteria was similar to that of cefotaxime and moxalactam, but it was even more active than these compounds against all Proteus species. It was also highly active against Haemophilus influenzae and Neisseria gonorrhoeae, including beta-lactamase producers. Like cefotaxime and moxalactam, Or 13-9904 was approximately eightfold more active than carbenicillin against most isolates of Pseudomonas aeruginosa and also active against highly carbenicillin-resistant isolates, but it was relatively inactive against moderately carbenicillin-resistant isolates. Ro 13-9904 also resembled cefotaxime and moxalactam in that it was active, though less so than cephaloridine, against staphylococci and streptococci, except for methicillin-resistant staphylococci and Streptococcus faecalis, which were resistant to it. It was less active than cefoxitin but slightly more active than ampicillin against both Bacteroides fragilis and other Bacteroides spp. Ro 13-9904 was resistant to most beta-lactamases but was attacked by enzymes from B. fragilis, isolates of indole-positive Proteus species, and also by a cefoxitin-hydrolyzing enzyme from an isolate of Enterobacter cloacae.