Comparative activity of ceftazidime and four other cephalosporins against gram-negative bacteria and their sensitivity to beta-lactamases.
The in vitro activity of ceftazidime compared with other beta-lactamase stable compounds was assessed against recent Gram-negative isolates. Three hundred forty-three bacterial strains were isolated from patients affected with UTI, identified by standard bacteriological methods and investigated for their production of beta-lactamases by the Nitrocefin test. MICs and MBCs (minimum inhibitory concentrations and minimum bactericidal concentration) of ceftazidime, cefamandole, cefoxitin, cefotaxime and cefuroxime were determined by a miniaturized dilution broth method against all beta-lactamase producing bacteria (129 out of 343). Sensitivity of the antibiotics to beta-lactamases isolated and semipurified by ultrasonic disruption and high-speed centrifugation was assessed by a spectrophotometric method. The in vitro antibacterial activity of each antibiotic was correlated to its sensitivity to isolated beta-lactamases. Ceftazidime showed lower MIC and MBC values and lower MBC/MIC ratios than the other compounds against all the bacteria including Pseudomonas spp. In addition, ceftazidime was not hydrolyzed significantly by any isolated beta-lactamases.
D002442:Ceftazidime / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006868:Hydrolysis; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000494:pharmacology*
D002511:Cephalosporins; D002442:Ceftazidime; D001618:beta-Lactamases