Azthreonam activity against gram-negative bacilli.

The in vitro activity of azthreonam - a monocyclic beta-lactam antibiotic - was compared with the activities of ampicillin, cephalothin, cefuroxime, cefotaxime, cefoperazone, lamoxactam, ceftazidime, and N-formimidoyl thienamycin against 249 clinical isolates of gram-negative bacilli. Azthreonam was as active or more active than all the third-generation cephalosporins against all the Enterobacteriaceae except Klebsiella. Against Klebsiella azthreonam was more active than cefoperazone but less active than the other third-generation cephalosporins. Azthreonam, ceftazidime, and piperacillin were equally active against Pseudomonas aeruginosa.