ANTIBIOTIC-RESISTANT PATHOGENS, SUCH AS ENTEROCOCOCO-VANCOMYCIN-RESISTANT (REV) ARE A GROWING PROBLEM IN HOSPITALISED PATIENTS AND OFTEN CAUSE INFECTIONS AFTER ANTIBIOTIC TREATMENT. ERV INFECTIONS USUALLY START IN THE INTESTINE. UNDER NORMAL CONDITIONS, OUR INTESTINE IS COLONISED BY HUNDREDS OF COMMENSAL BACTERIA, THE MICROBIOTA, WHICH INHIBITS INTESTINAL COLONISATION BY VRE, WHICH IS CALLED “COLONISATION RESISTANCE” (CR). CONVERSELY, THE ADMINISTRATION OF ANTIBIOTICS ALTERS THE COMPOSITION OF THE MICROBIOTA WHICH ALLOWS VRE TO COLONISE THE INTESTINE AND THEN SPREAD TO BLOOD WHERE IT CAN ENDANGER THE PATIENT’S LIFE. THEREFORE, UNDERSTANDING HOW AND WHAT MEMBERS OF THE MICROBIOTA CONFER CR AND HOW ANTIBIOTICS PROMOTE INFECTION IS CRUCIAL IF WE WANT TO PREVENT VRE INFECTIONS. HOWEVER, THE ABSENCE OF TECHNIQUES TO ANALYSE THE MICROBIOTA HAS MADE IT DIFFICULT TO STUDY THIS CLINICALLY RELEVANT FIELD. FORTUNATELY, NEW MASS SEQUENCING TECHNIQUES NOW ALLOW THE DETAILED STUDY OF THE MICROBIOTA AND ITS GENES (MICROBIOME). OUR GROUP HAS PIONEERED THIS NEW METHODOLOGY TO IDENTIFY MICROBIOTA CHANGES THAT PROMOTE VRE COLONISATION AND IDENTIFY THOSE BACTERIAL SPECIES THAT CONFER CR. WE HAVE SHOWN THAT THE REMOVAL OF CERTAIN BACTERIA FROM THE MICROBIOTA, INCLUDING BARNESIELLA, RUMINOCOCCACEAE, LACHNOSPIRACEAE, ALISTIPES, ALLOBACULUM, INCREASES THE RISK OF INFECTION. MOREOVER, THE RECONSTITUTION OF MICE TREATED WITH ANTIBIOTICS WITH THESE BACTERIA CONSIDERABLY DECREASES THE COLONISATION BY VRE. HAVING IDENTIFIED SPECIFIC MICROBIOTA BACTERIA THAT PROMOTE CR, IN THIS PROJECT WE PROPOSE TO IDENTIFY THE MECHANISMS BY WHICH THESE BACTERIA CONFER PROTECTION. OUR PUBLISHED RESULTS INDICATE THAT THE MICROBIOTA CONFERS CR IN THE ABSENCE OF ESSENTIAL COMPONENTS OF THE IMMUNE SYSTEM. THEREFORE, IN THIS PROJECT WE WILL FOCUS ON IDENTIFYING MECHANISMS BY WHICH THE MICROBIOTA DIRECTLY CONFERS RESISTANCE (COMPETICION BY NUTRIENTS, PRODUCTION OF INHIBITORY SUBSTANCES). TO ACHIEVE THIS GOAL, WE WILL FIRST DEFINE THE NUTRIENTS USED BY THE PATHOGEN AND PROTECTIVE BACTERIA (BPS) IN THE MICE INTESTINE. FOR THIS WE WILL USE OMIC TECHNIQUES (METAGENOMICA AND METATRANSCRIPTOMICA) TO IDENTIFY GENES EXPRESSED TO ACQUIRE IN VIVO NUTRIENTS, AND METABOLOMIC TECHNIQUES TO IDENTIFY NUTRIENTS THAT HAVE DECREASED IN VIVO AFTER COLONISATION BY VRE OR BPS. IN ADDITION, WE WILL IDENTIFY IN VITRO BY “ARRAYS” THE NUTRIENTS THAT ARE ESSENTIAL FOR THE GROWTH OF VRE, AND BY MEANS OF A TECHNIQUE OF IDENTIFICATION OF MUTANTS BY TRANSPOSITION IN VIVO, WE WILL IDENTIFY GENES THAT VRE NEEDS TO COLONISE THE INTESTINE AND ACQUIRE NUTRIENTS. ONCE THE STRATEGIES USED BY VRE AND BPS TO EXPLOIT NUTRIENTS HAVE BEEN DEFINED, IN VITRO AND IN VIVO COMPETICION TESTS WILL DEMONSTRATE THE ROLE OF NUTRIENT COMPETITION IN CR VERSUS VRE. ON THE OTHER HAND, THE IN VIVO OMIC PROFILES OF BPS WILL IDENTIFY POSSIBLE INHIBITOR MOLECULES THAT WILL BE TESTED IN GROWTH INHIBITION ASSAYS TO DEFINE THE ROLE OF THESE MOLECULES IN CR. THE INFORMATION OBTAINED IN THIS PROJECT WILL GIVE RISE TO NEW THERAPEUTIC STRATEGIES TO COMBAT ERV INFECTIONS, A PATHOGEN THAT IS ACQUIRING RESISTANCE TO THE FEW THERAPEUTIC OPTIONS AVAILABLE.
