CGP 31523A

The in vitro activity of CGP 31523A, an aminothiazolyl cephem, was compared to that of other cephalosporins--imipenem, aztreonam, carbenicillin, and gentamicin. CGP 31523A inhibited E. coli, K. pneumoniae, P. mirabilis, C. diversus, K. oxytoca, P. stuartii, Salmonella and Shigella at less than or equal to 0.25 micrograms/ml. It was equal or 2-fold more active than cefotaxime and ceftazidime, and 4-fold more active than imipenem against these organisms. It inhibited all carbenicillin and gentamicin-resistant isolates of these species. Neisseria and Haemophilus were inhibited by less than or equal to 0.12 micrograms/ml. Some C. freundii, E. cloacae, E. aerogenes, P. vulgaris, and P. penneri had MICs greater than or equal to 16 micrograms/ml similar to cefotaxime, ceftazidime and aztreonam. Pseudomonas were resistant, MIC 128 micrograms/ml. CGP 31523A inhibited streptococci at less than or equal to 0.25 micrograms/ml with the exception of S. faecalis, and staphylococci were inhibited by 0.5 micrograms/ml but methicillin-resistant isolates were resistant. Bacteroides and some Clostridium had MICs greater than or equal to 16 micrograms/ml. CGP 31523A was less stable than cefotaxime and ceftazidime to the plasmid TEM/SHV/PSE-4 beta-lactamases. Like cefotaxime it was hydrolyzed by the P. vulgaris type Ic beta-lactamase but not by the type Ia enzymes. CGP 31523A was not an effective beta-lactamase inhibitor nor did it induce beta-lactamases. It had overall activity comparable to available extended spectrum cephalosporins.

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.