Enhanced growth of Staphylococcus aureus after nitric oxide supplementation during simulated extracorporeal circulation.

BACKGROUND: Several factors contribute to postoperative bacterial infections in cardiac surgery. Long operation times and the use of extracorporeal circulation increase the risk of infection. Nitric oxide has been shown to possess a broad spectrum antimicrobial effect. METHODS: In this study, we investigated the effect of nitric oxide on S. AUREUS growth in whole blood during simulated extracorporeal circulation. RESULTS: S. AUREUS growth increased 6.2-fold after 180 min SECC in the presence of nitric oxide. Leukocyte counts remained unchanged without any differences between the groups. We observed a steady increase in markers of oxidative stress and activity of the innate immune system. Myeloperoxidase levels increased 8-fold, and C3a and terminal complement complex by 2-fold after 180 min. CONCLUSION: S. AUREUS growth is not due to the effect of nitric oxide on the innate immune system but from its effect on the bacteria itself. It has been shown that nitric oxide stimulates the expression of inducible lactate dehydrogenase, specific to S. AUREUS, which improves its resistance to oxidative stress, and may give S. AUREUS a survival advantage resulting in increased growth.