A study of cefoperazone alone and in combination with tobramycin against Pseudomonas aeruginosa

The minimum inhibitory concentrations (MICs) of cefoperazone for 507 clinical isolates of Pseudomonas aeruginosa were measured by plate dilution technique. On a cumulative percentage basis, 81% of isolates were inhibited by less than or equal 3.13 microgram/ml of cefoperazone. The minimum bactericidal concentration (MBC) was found to be generally twice the MIC. Synergy occurred between cefoperazone and tobramycin, judged by a lowering of the MIC in 69% of isolates, for which the MIC of cefoperazone alone was less than or equal to 6.2 microgram/ml.