Abstract
BackgroundEnterococcus faecalis, generally considered as a saprophytic bowel commensal, has recently emerged as an important nosocomial pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis. This bacterium is capable of forming biofilms on various surfaces and its high level of antibiotic resistance contributes to its pathogenicity. The aim of this study was to evaluate the effect on E. faecalis, of Substance P (SP), an antimicrobial peptide that is produced in the gut and skin.ResultsWe found that SP did not have antibacterial activity against E. faecalis V583 (MIC >1000 µg/ml). Conversely, SP stimulated aggregation, hydrophobicity, lactic acid and tyramine production in this bacterium. The cytotoxicity and bacterial translocation were also accelerated when E. faecalis V583 were pretreated with SP before infection of intestinal Caco-2/TC7 cells.ConclusionSP can modulate the physiology of E. faecalis. Extensive studies are now needed to screen within the human microbiota which bacteria are responsive to host molecules, and to identify their sensors.
Highlights
Enterococcus faecalis, generally considered as a saprophytic bowel commensal, has recently emerged as an important nosocomial pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis
A treatment with 10−2 M Substance P (SP) led to approximately 50% of red bacteria demonstrating dead cells stained with propidium iodide (PI) (Fig. 1d), Minimal inhibitory concentration (MIC) analysis had not shown antimicrobial activity even for high concentrations of SP
Confocal observations showed that bacteria seem to slightly agglutinate when exposed to 10−4 or 10−2 M SP compared to untreated bacteria and bacteria exposed to 10−6 M
Summary
Enterococcus faecalis, generally considered as a saprophytic bowel commensal, has recently emerged as an important nosocomial pathogen causing severe urinary tract infections, surgical wound infections, bacteremia, and bacterial endocarditis. Some strains, such as E. faecalis V583, are known to be opportunistic pathogen This bacterium originates from a patient suffering from a persistent bloodstream infection, and it can cause diseases like urinary tract infections, bacteremia, and infective endocarditis in immunocompromised patients [17, 18]. These infections may be problematic because some E. faecalis strains are resistant to many antibiotics including vancomycin, and Enterococci are considered among the most prevalent nosocomial pathogens [19, 20]. A recent study showed that commensal strains of E. faecalis generally protect the gut by producing pheromone peptides that can kill MDR E. faecalis V583 [21]
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