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The in vitro activity of ceftizoxime compared with other beta-lactamase stable compounds was assessed against recent urinary gram negative isolates. 343 bacterial strains were isolated from patients affected by UTI, identified by standard bacteriological methods and investigated for their production of beta-lactamases by Nitrocefin test. MICs and MBCs of ceftizoxime, ceftriaxone, cefamandole, cefoxitin and cefotaxime were determined by a miniaturized dilution broth method against all beta-lactamase producing bacteria (129 out of 343). Sensitivity of antibiotics to beta-lactamases isolated and semi-purified by ultrasonic disruption and high speed centrifugation was assessed by a spectrophotometric method. In vitro antibacterial activity of each antibiotics was correlated to their sensitivity to isolated beta-lactamases. Ceftizoxime showed lower MIC and MBC values and lower MBC/MIC ratio than the other compounds against all the bacteria including Pseudomonas. Ceftizoxime was not hydrolized by any isolated beta-lactamase.

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.