Large-Scale Screening of a Targeted Enterococcus faecalis Mutant Library Identifies Envelope Fitness Factors

Spread of antibiotic resistance among bacteria responsible for nosocomial and community-acquired infections urges for novel therapeutic or prophylactic targets and for innovative pathogen-specific antibacterial compounds. Major challenges are posed by opportunistic pathogens belonging to the low GC% Gram-positive bacteria. Among those, Enterococcus faecalis is a leading cause of hospital-acquired infections associated with life-threatening issues and increased hospital costs. To better understand the molecular properties of enterococci that may be required for virulence, and that may explain the emergence of these bacteria in nosocomial infections, we performed the first large-scale functional analysis of E. faecalis V583, the first vancomycin-resistant isolate from a human bloodstream infection. E. faecalis V583 is within the high-risk clonal complex 2 group, which comprises mostly isolates derived from hospital infections worldwide. We conducted broad-range screenings of candidate genes likely involved in host adaptation (e.g., colonization and/or virulence). For this purpose, a library was constructed of targeted insertion mutations in 177 genes encoding putative surface or stress-response factors. Individual mutants were subsequently tested for their i) resistance to oxidative stress, ii) antibiotic resistance, iii) resistance to opsonophagocytosis, iv) adherence to the human colon carcinoma Caco-2 epithelial cells and v) virulence in a surrogate insect model. Our results identified a number of factors that are involved in the interaction between enterococci and their host environments. Their predicted functions highlight the importance of cell envelope glycopolymers in E. faecalis host adaptation. This study provides a valuable genetic database for understanding the steps leading E. faecalis to opportunistic virulence

Dysbiosis in inflammatory bowel diseases: the oxygen hypothesis

The healthy intestine is characterized by a low level of oxygen and by the presence of large bacterial communities of obligate anaerobes. Dysbiosis of the gut microbiota has been reported in patients suffering from inflammatory bowel diseases (IBDs), but the mechanisms causing this imbalance remain unknown. Observations have included a decrease in obligate anaerobes of the phylum Firmicutes and an increase in facultative anaerobes, including members of the family Enterobacteriaceae. The shift of bacterial communities from obligate to facultative anaerobes strongly suggests a disruption in anaerobiosis and points to a role for oxygen in intestinal dysbiosis. Proposals to evaluate this hypothesis of a role for oxygen in IBD dysbiosis are provided. If this hypothesis is confirmed, decreasing oxygen in the intestine could open novel means to rebalance the microbiota and could provide novel preventative or therapeutic strategies for IBD patients in whom current treatments are ineffective

Recherche d'une acquisition par des Rhizobium leguminosarum bv. viciae génétiquement modifiés introduits dans un champ d'éléments génétiques en provenance de la population indigène

163 ref. *INRA, centre de recherches de Dijon (FRA) Diffusion du document : INRA, centre de recherches de Dijon (FRA) Diplôme : Dr. d'Universit

Analyse moléculaire de la flore colique

National audienc

Characterization, distribution, and localization of ISRl2, an insertion sequence element isolated from Rhizobium leguminosarum bv. viciae

International audienc

Analyse de la microflore intestinale humaine par hybridation in situ par des sondes fluorescentes ciblant l'ARNr 16S

National audienc

Fluorescent Pseudomonas species categorized by using polymerase chain reaction (PCR)/restriction fragment analysis of 16S rDNA

International audienc

Long-term storage of human fecal samples for in situ hybridization analysis of gut microbiota composition

International audienc

Acquisition of genes from indigenous bacteria at long term release sites: isolation and distribution of two insertion sequences within the indigenous population of Rhizobium leguminosarum by viciae

International audienc