In Vitro Sensitivity of Isolates of Pseudomonas Aeruginosa to Carbenicillin, Gentamicin, Tobramycin, and Some other Antibiotics

In vitro sensitivity of 152 clinical isolates of Pseudomonas aeruginosa to 8 antibiotics was determined by an agar dilution method. Almost all strains were sensitive to tobramycin, gentamicin, and colistin in concentrations attainable in serum during therapy. Tobramycin was 8 times as effective as gentamicin on a weight basis. Gentamicin in turn was 4 to 8 times as effective as streptomycin. 11.2% of the strains were resistant to 512 μg/ml carbenicillin, a remarkably high figure, since carbenicillin had been used only to a negligible extent in the environment from which the strains were collected.