Effect of Hyperbaric Oxygen on Aerobic Bacteria in vitro and in vivo.

Strains of E. coli, A. aerogenes, P. aeruginosa, S. typhimurium, P. tnirabilis, D. pneumoniae, S. aureus, and Strep, pyo-genes in broth multiply in oxygen at 30 pounds per square inch absolute (p.s.i.a.). The rate of growth and the peak titer achieved were frequently inhibited in oxygen as compared with air at 15 p.s.i.a. The inhibitory effect of oxygen was most marked with S. typhimurium, D. pneumoniae and S. aureus and was minimal or absent with P. mirabilis, A. aerogenes and E. coli. In general, 24-hour cultures were more susceptible to the inhibitory activity of oxygen than were 4-hour cultures. Each of the strains of aerobic bacteria grew on the surfaces of agar plates when incubated in oxygen or air. Although equal numbers of colonies developed in oxygen and air? differences in colonial morphology were noted in some of the strains incubated in oxygen. Exposure to oxygen at 45 p.s.i.a. did not protect mice against death from infection produced by intravenous administration of D. pneumoniae, S. aureus, or S. typhimurium.