736. The Use of Bacteriophages to Inhibit Different Strains of Vancomycin-Resistant or Susceptible Enterococci

Abstract

Background. Vancomycin-resistant Enterococci (VRE) is a well-known infectious complication among immunocompromised patients, especially hematopoietic cell transplant (HCT) recipients. VRE colonization of the gastrointestinal tract could be associated with VRE bacteremia and worse outcomes in HCT recipients. The use of systemic antibiotics to eradicate VRE colonization is highly discouraged because of the lack of efficacy, the rapid onset of antibiotic resistance, and the disruption of the normal microbiota. Bacteriophages (phages) may constitute a good alternative to antibiotics to eliminate specific pathogens without disrupting the patient's normal microbiota. Methods. Sewage samples were collected from the City of Houston for phages isolation. Samples were centrifuged, filtered and exposed to several targeted VRE host strains. After several amplification, the final filtrate was titrated and checked for the presence of VRE-specific phages. Isolated phages were observed under electron microscopy and were tested against multiple VRE strains isolated from different sources including patients' stool samples, patients' room environment, sewage samples, clinical isolates of daptomycin-resistant VRE strains or vancomycin-susceptible Enterococcus faecium (VSEF) and Enterococcus faecalis (VSEf) strains. Results. Four VRE-specific phages were isolated from sewage samples (MDA1, MDA2, MDA3, and MDA4). All phages belong to the Caudovirales order. Phage MDA1 belongs to the Podoviridae family, phage MDA2 is a Siphoviridae, whereas MDA3 and MDA4 belong to the Myoviridae family (Figure 1A). All phages were lytic and were able to inhibit at least four VRE strains and only MDA1 had activity against VSEF and MDA4 against VSEf. The efficacy of these lytic phages complemented one another as the combination of these four phages inhibited all different VRE strains (Figure 1B). Conclusion. Our results highlight the feasibility and the potential success of these phages in inhibiting VRE in vitro. These VRE-specific phage cocktails may be used in future studies to reduce VRE colonization and subsequent infections in HCT recipients. (Figure Presented) .