title: Beta lactamase resistance of newer cephalosporins and antimicrobial effectiveness against gram-negative bacilli.
abstract: Three newer cephalosporins (cefamandole, cefoxitin and cefazaflur) were investigated, in comparison with three older agents (cephalothin, cephaloridine and cefazolin) to determine their stability to beta-lactamases of gram-negative bacilli, and to correlate this with their antibacterial activity. Nine of the 17 bacterial strains employed produced broadspectrum beta-lactamases; the remaining eight produced cephalosporinases. The cephalosporins were highly active against bacteria producing broad-spectrum beta-lactamases; they were less active against organisms producing cephalosporinases. All of the cephalosporinase-producing strains were resistant to cephalothin anc cephaloridine. With the other cephalosporins the correlation between hydrolysis by cephalosporinases and resistance of the organisms was poor. Four to eight cephalosporinase-producing strains were resistant to cefoxitin, which was completely resistant to hydrolysis by the beta-lactamases. Cefozolin, cefamandole and cefazaflur inhibited several of these strains in spite of destruction by the beta-lactamase. Several cephalosporins need to be used in antimicrobial susceptibility testing of gram-negative bacilli.
mesh_terms: D000581:Amidohydrolases / Q000096:biosynthesis*; D002435:Cefamandole / Q000494:pharmacology; D002437:Cefazolin / Q000494:pharmacology; D002440:Cefoxitin / Q000494:pharmacology; D002509:Cephaloridine / Q000494:pharmacology; D002510:Cephalosporinase / Q000096:biosynthesis*; D002511:Cephalosporins / Q000494:pharmacology*; D002512:Cephalothin / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology; D010405:Penicillinase / Q000096:biosynthesis*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology
chemical_list: D002511:Cephalosporins; D002435:Cefamandole; D002440:Cefoxitin; D000581:Amidohydrolases; D002510:Cephalosporinase; D010405:Penicillinase; D002437:Cefazolin; D002509:Cephaloridine; D002512:Cephalothin