In vitro activity of CGP 31523A, a broad-spectrum cephalosporin, in comparison with those of other agents.

The in vitro activity of CGP 31523A, a new aminothiazolyl cephalosporin, was compared with those of cefoxitin, cefuroxime, moxalactam, piperacillin, ciprofloxacin, and other beta-lactams, when appropriate, against 533 recent clinical isolates and known resistant strains of bacteria. The MICs of CGP 31523A required to inhibit 90% (MIC90S) of the members of the family Enterobacteriaceae, Neisseria gonorrhoeae, and Streptococcus pneumoniae were less than or equal to 0.25 micrograms/ml. Of Staphylococcus aureus (excluding methicillin-resistant strains) and Haemophilus influenzae, 90% were susceptible to 0.5 micrograms/ml. Pseudomonas aeruginosa and Lancefield group D streptococci were resistant to CGP 31523A (MIC90, greater than or equal to 128 micrograms/ml). The activity against Bacteroides fragilis was modest (MIC90, 32 micrograms/ml). The susceptibility of known beta-lactamase-producing strains suggested that CGP 31523A was resistant to many beta-lactamases (but not those of Bacteroides fragilis). The serum protein binding of CGP 31523A was about 73%. The primary target site of CGP 31523A in Escherichia coli appeared to be penicillin-binding protein 3.