In-vitro activity of BRL-36650, a novel beta-lactamase-stable penicillin, against multiply resistant gram-negative organisms.

The in-vitro activity of BRL-36650, a novel beta-lactamase-stable penicillin was tested in comparison with that of cefotaxime, ceftazidime, aztreonam and imipenem against 559 multiply resistant Gram-negative organisms, some of which were also resistant to third generation cephalosporins. BRL-36650 and imipenem were the most active antibiotics. Against 342 Enterobacteriaceae the MICs90 were: imipenem 2 mg/l, BRL-36650 4 mg/l, aztreonam 8 mg/l and cefotaxime 32 mg/l. Against 122 Pseudomonas aeruginosa the MICs90 were: BRL-36650 4 mg/l, imipenem 8 mg/l, aztreonam and ceftazidime 64 mg/l.