Surgical site infections and the role of anesthesia and bacterial ion transporters

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Project Summary/ Abstract The proposed research titled “Surgical site infections and the role of anesthesia and bacterial ion transporters” is to study the impact of daily used anesthetic drugs on surgical site infections (SSIs) (exposure duration and type of anesthetics) and the effectiveness of antibiotics in vivo and examine its underlying mechanism in vitro under the hypothesis that volatile anesthetics (VAs), not intravenous anesthetic (IA) increase bacteria burden in surgical wound by increasing biofilm formation via their direct interaction with bacterial ion transporters, and also by attenuating host immune cells. SSIs are the most common surgical infections in the perioperative setting, occupying 20% of in-hospital infections, and associated with significant morbidities, mortalities and healthcare expenses. Up to 80% of SSIs are due to bacteria in biofilm form, not in planktonic form. We previously reported in gram-negative bacteria Escherichia coli that 1) commonly used VAs isoflurane and sevoflurane, not IA propofol increased biofilm formation, and 2) a group of bacterial ion transporters were involved in biofilm formation, and 3) VAs enhanced the biofilm formation via affecting ion transporters. In this proposal we plan to use gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis strains, common strains for SSIs. In Aim 1, we will determine the effect of common anesthetics on biofilm formation in vitro under hypoxia to mimic oxygen level at wounds. The role of ion transporters in biofilm formation and their direct interaction with VAs will be examined. In Aim 2, we will determine the effect of common anesthetics on host defense, including phagocytosis of planktonic or biofilm bacteria cells in vitro under hypoxia and direct binding of VA to gram-positive receptor toll-like receptor 2. In Aim 3, we will determine the impact of anesthetics on biofilm-associated SSIs and the effectiveness of antibiotics in vivo. We will study the effect of anesthetics on bacterial biofilm formation and innate immune cell functions in this model. Upon the completion of the study, we expect to learn whether or not the type of anesthetics and the duration of their exposure affect bacterial loads, biofilm formation and the effectiveness of antibiotics. All the anesthetics tested are in clinical use and we expect that our study is highly clinically-relevant and readily translatable. Following the successful completion of this study, we expect to have the foundation to examine the impact of anesthetic regimens on SSIs in patients undergoing procedures with high risk of infection. The knowledge of anesthetic direct binding to bacterial ion transporters for biofilm formation and to host defense receptor toll-like receptor 2, if learned in this proposal, will not only increase our understanding of how volatile anesthetics work but also can lead us to think of developing screening assays to rule out these interactions and develop anesthetics devoid of adverse effects.