[Application of a millipore membrane transfer method to the study of the activity of 4 beta-lactams on Pseudomonas aeruginosa].

In vitro activities of four cephalosporins, i.e. cefoperazone, cefsulodin, ceftazidime and CM 40874, on 31 ticarcillin-susceptible or resistant Pseudomonas aeruginosa strains were compared. Minimal inhibitory and bactericidal concentrations were determined by the conventional broth technique and by a filter membrane transfer method on agar. MICs determined by both methods were comparable for each strain. Some discrepancies were found for minimal bactericidal concentrations. Among the cephalosporins studied on ticarcillin-susceptible Pseudomonas aeruginosa strains, the most active was ceftazidime, followed by cefsulodin, CM 40874 and cefoperazone. Resistance of Pseudomonas aeruginosa to ticarcillin was associated with an overall increase in resistance to the four cephalosporins studied. These cephalosporins can be classified according to bacteriostatic and bactericidal effect in the following decreasing order: ceftazidime, CM 40874, cefsulodin and cefoperazone.