Potential use of probiotic and commensal bacteria as non-antibiotic strategies against vancomycin-resistant enterococci.

Vancomycin-resistant enterococci (VRE) represent major opportunistic pathogens in immunocompromised populations. Particularly adapted to the hospital environment, VRE efficiently colonize the gastrointestinal (GI) tract of patients. Furthermore, certain circumstances of antibiotic-induced dysbiosis of the gut microbiota contribute to colonization, overgrowth and persistence of VRE in the GI tract, increasing the risk of infection in critically ill and/or severally immunocompromised patients. VRE treatment with antibiotics remains challenging due to the robustness and ability of enterococci to adapt to harsh conditions and to acquire novel resistance genes. Reducing VRE intestinal colonization, overgrowth and carriage has thus become an important issue to reduce the risk of infection and dissemination. This review summarizes the knowledge of the conditions favoring VRE colonization and persistence in the GI tract and focuses on the strategies to reduce overgrowth or persistence of VRE in the GI tract based on the oral administration of probiotic or commensal bacteria in human studies and in animal models, and on the potential underlying mechanisms of the anti-VRE effect.