MECHANISTIC BASIS OF BACTERIOPHAGES FOR THE DECOLONIZATION OF VANCOMYCIN RESISTANT ENTEROCOCCI IN THE INTESTINE.

Project Summary/AbstractThe incidence of multidrug resistant (MDR) bacterial infections is rising. This is particularly relevant for the Gram-positive bacterium Enterococcus faecalis, an opportunistic pathogen and leading cause of nosocomialbacteremia. The rise in MDR E. faecalis infections is largely attributed to their ability to resist many antibioticsincluding antibiotics of ?last resort?, such as vancomycin. E. faecalis is a native inhabitant of the human intestinaltract which serves as a major reservoir of MDR E. faecalis. Antibiotic depletion of the intestinal microbiota canfacilitate blooms of E. faecalis leading to their enhanced dissemination to the bloodstream and other tissue sites.In many cases overgrowth of intestinal enterococci is dominated by vancomycin resistant enterococci (VRE)which severely limits available treatment options. With increasing VRE infections worldwide, it is imperative thatnew strategies for therapeutic intervention are explored. An alternative to traditional antibiotics is the use ofbiological agents for the treatment of drug resistant bacterial infections. One approach is harnessingbacteriophages (phages) that infect and kill bacteria. Although phages may hold promise as next generationtherapeutics, we know little of the basic principles of phage infection processes in vivo and how the mammalianhost environment influences phage-bacteria interactions. This project investigates the use of phages for thedecolonization of VRE within its natural intestinal habitat. Using a combination of mouse intestinal colonizationmodels, molecular genetics and whole genome sequencing, we aim to gain mechanistic insight into howintestinal selective pressures influence the infectivity and genome evolution of phages during phage-mediatedVRE decolonization. To achieve this goal we will execute three specific aims: 1) Define the intestinal selectivepressures that dictate phage-mediated E. faecalis decolonization, 2) Determine the long-term stability andgenomic evolution of E. faecalis phages in the intestine, and 3) Determine cognate receptors for diverseE. faecalis phages and delineate receptor function. Understanding intestinal selective pressures andmolecular mechanisms of enterococcal phage infection in vivo will aid in the development of novel phagetherapeutics for the decolonization of enterococci recalcitrant to conventional antibiotics.