Unpredictable response of Pseudomonas aeruginosa to synergistic antibiotic combinations in vitro.

The combined activity of ticarcillin and each of three aminoglycosides, gentamicin, tobramycin, and amikacin, was studied with 45 clinical isolates of Pseudomonas aeruginosa. All strains individually were susceptible to each of these agents. Comparison of the results revealed highly variable interaction, both from strain to strain and from one aminoglycoside to another against the same strain.