Synergism between hyperoxia and antibiotics for Pseudomonas aeruginosa.

Three strains of Pseudomonas aeruginosa were directly exposed on the surface of membrane filters to hyperoxic atmospheres. One of the three strains was found to be sensitive to oxygen. Colonies failed to appear during 18 hr of incubation in pure oxygen at 1 atm, but about 40% of the bacteria recovered to produce colonies upon reincubation in air. Similar killing was produced by 10 hr of oxygen exposure. No inhibition or killing was observed with two other strains. Streptomycin (1mug/ml) and kanamycin (5mug/ml) were more effective in killing the oxygen-sensitive strain in the presence of 60 to 70% oxygen than in air, but polymyxin B (5mug/ml) did not show a synergistic effect under such conditions.