R. M. Boudreau1, G. E. Martin1, C. Couch1, A. E. Mahdy1, M. J. Edwards1, E. Gulbins1,2, A. P. Seitz1, P. L. Jernigan1 1University Of Cincinnati,Department Of Surgery,Cincinnati, OH, USA 2Universitat Duisburg-Essen,Division Of Molecular Biology,Essen, NORTH RHINE-WESTPHALIA, Germany
Introduction: Catheter-associated bacteriuria is the most frequently diagnosed nosocomial infection globally. The conventional treatment of these infections with systemic antibiotics creates an opportunity for the selection of antimicrobial resistance, adds to burgeoning medical costs, and increases the risk for antibiotic-related side effects. Furthermore, this approach remains suboptimal, with approximately one-quarter of acutely infected patients developing recurrent infection. Sphingosine, a membrane sphingolipid with broad-spectrum anti-microbial properties, has been described as an important part of the innate immunity of the respiratory epithelium to bacterial invasion. Our group has recently discovered high amounts of sphingosine in the transitional epithelium of mouse bladders. We hypothesize that sphingosine is important in the bladder’s innate immunity and that exogenous sphingosine may serve as an effective anti-microbial in murine models of E. coli UTI.
Methods: E. coli was incubated with normal saline control or varying concentrations of sphingosine in vitro for 2 hours at 37C and 125 rpm agitation. Bacterial growth was quantified by the plate-dilution method. To evaluate sphingosine’s effectiveness in vivo, wild type mice were sterilely catheterized and inoculated with E. coli for one hour before undergoing bladder irrigation with normal saline control or varying concentrations of sphingosine. Bladders were then harvested and homogenized; and bacterial load was quantified by the plate-dilution method.
Results: Sphingosine demonstrated impressive killing of E. coli compared to saline control in our in vitro study (94% reduction, p<0.001). Similarly, in our murine model of UTI, the bladder irrigations showed maintenance of this antimicrobial effect (Table 1, 95% reduction vs. saline control, p=0.007).
Conclusion: It was demonstrated previously that sphingosine both plays a crucial role in innate mucosal immunity and possesses antimicrobial activity against E. coli in solution. Here, we present the first study to demonstrate that exogenous sphingosine causes effective bacterial killing in a murine model of UTI. Our data support the need for further investigation toward a possible role for sphingosine-based bladder irrigation in the management of UTIs.
