BACKGROUND: S. aureus infective endocarditis (IE) is a serious disease an in-hospital mortality of up to 40%. Improvements of effects of antibiotics and host responses could potentially benefit outcomes. Hyperbaric oxygen treatment (HBOT) represents an adjunctive therapeutic option. We evaluated the efficacy of HBOT in combination with tobramycin in S. aureus IE.

METHODS: A rat model of S. aureus IE mimicking the bacterial load in humans was used. Infected rats treated with tobramycin were randomized into two groups, 1) HBOT (b.i.d) or 2) normobaric air breathing (non-HBOT). Quantitative bacteriology, cytokine expression, valve vegetation size and clinical status were assessed 4 days post infection.

RESULTS: Adjunctive HBOT (n=13) reduced bacterial load in the aortic valves, myocardium and spleen compared to the non-HBOT group (n=17) (p=.04, p<.001, and p =.01, respectively) and improved the clinical score (p <.0003). Photoplanimetric analysis and weight of valve vegetations showed significantly reduced vegetations in the HBOT group (p <.001). Key pro-inflammatory cytokines (IL-1b, IL-6, KC and VEGF) were significantly reduced in valves from the HBOT group compared to the non-HBOT group.

CONCLUSION: HBOT augmented tobramycin efficacy as assessed by several parameters. The present findings suggest the potential use of adjunctive therapy in severe S. aureus IE.