Biological activity of BO-1236, a new antipseudomonal cephalosporin.

BO-1236, a new cephalosporin having an N-methyl-5,6-dihydroxyisoindolinium moiety on the 3-methylene of the cephem, showed potent activity against gram-negative organisms, including Pseudomonas aeruginosa. The in vitro activity of BO-1236 was superior or comparable to that of ceftazidime, cefotaxime, and cefoperazone in susceptibility tests with clinical isolates. BO-1236 was significantly more active than ceftazidime against P. aeruginosa strains susceptible or resistant to ceftazidime or gentamicin or both. MBCs were usually close to MICs, both of which were influenced by inoculum size to about the same degree as those of the other beta-lactams. BO-1236 was stable to all types of beta-lactamases except type I oxyiminocephalosporin-hydrolyzing enzyme, by which BO-1236 was slightly hydrolyzed. BO-1236 showed protective activity superior to that of ceftazidime and cefotaxime in experimental infections in mice caused by two strains of P. aeruginosa and showed activity comparable to that of ceftazidime and cefotaxime against other gram-negative bacterial infections.