Hyperoxia and the antimicrobial susceptibility of Escherichia coli and Pseudomonas aeruginosa

Abstract

We have tested the ability of hyperoxia (98% 02-2% CO2 at 2.8 atmospheres absolute [ca. 284.6 kPa]) to enhance killing of Escherichia coli (serotype 018 or ATCC 25922) by nitrofurantoin, sulfamethoxazole, trimethoprim, gentamicin, and tobramycin. We have also looked for interactions between hyperoxia and the aminoglycosides against Pseudomonas aeruginosa ATCC 27853. Hyperoxia significantly enhanced bacteriostatic activity of nitrofurantoin and trimethoprim as measured by MIC testing. The possibility exists that these effects might be due to the method required to test MICs under hyperoxic conditions rather than to the effect of hyperoxia itself. In addition, hyperoxia enhanced killing of bacteria by trimethoprim as measured by MBC testing. Hyperoxia decreased numbers of E. coli by 1.3 loglo and P. aeruginosa by 2.7 log1o in cationsupplemented Mueller-Hinton broth medium. The bacteriostatic effects of hyperoxia did not affect MICs of gentamicin or tobramycin. The lack of interaction between hyperoxia and gentamicin or tobramycin was confirmed by determining the number of viable bacteria remaining after 24 h of exposure to hyperoxia by using a pour plate method. We conclude that hyperoxia potentiates the antimicrobial activity of the reductionoxidation-cycling antibiotic tested (nitrofurantoin) and of one of the antimetabolites tested (trimethoprim). Hyperoxia does not enhance the bactericidal effects of gentamicin and tobramycin, which require oxidative metabolism for transport into bacterial cells.

Hyperoxia prolongs the aminoglycoside-induced postantibiotic effect in Pseudomonas aeruginosa

“…After the 1-h exposure, tobramycin was removed and the bacteria were incubated under normoxic conditions. The maximal killing of P. aeruginosa which occurred under normoxic conditions is in agreement with our previous work (25) (31), who found that hyperoxia enhances the growth of E. coli. Aminoglycoside uptake by bacteria has been shown to be dependent upon growth rates or quinonedependent bacterial respiration (26,27,29).…”

“…Exposure to hyperbaric oxygen for 18 to 24 h inhibited the growth of P. aeruginosa (4,19,25 (12). Hyperoxia may extend the in vivo PAE and therefore prolong the therapeutic activity of aminoglycosides in patients exposed to hyperoxia or hyperbaric oxygen.…”

“…Hyperbaric oxygen and sodium sulfisoxazole increased the survival of V. anguillarum-infected goldfish more than threefold (20). Hyperoxia enhanced the bacteriostatic activity of nitrofurantoin and both the bacteriostatic and bactericidal activities of trimethoprim against E. coli (25).…”

Effect of anterior chamber air bubble on prevention of experimental Staphylococcus epidermidis endophthalmitis

“…Air may have a bacteriostatic effect. Air components such as oxygen and carbon dioxide have bacteriostatic properties, and potentiate antibacterial effects of some antibiotics [17][18][19][20]. In addition, oxygen and nitrogen are used in the production of reactive oxygen and reactive nitrogen intermediates.…”

Effect of hyperbaric oxygen therapy on the duration of treatment of spinal tuberculosis

“…12 Despite controversy over the treatment of spinal tuberculosis, we added hyperbaric oxygen (HBO) therapy to our treatment protocol to take advantage of its proven antibactericidal effects. [15][16][17][18][19][20] Data obtained from control and study groups were compared to evaluate the effect of adjuvant HBO therapy on the duration of chemotherapy and rate of radiological improvement in spinal tuberculosis.…”