Importance of the ebp (endocarditis-and biofilm-associated pilus) locus in the pathogenesis of Enterococcus faecalis ascending urinary tract infection

Background. We recently demonstrated that the ubiquitous Enterococcus faecalis ebp (endocarditis- and biofilm-associated pilus) operon is important for biofilm formation and experimental endocarditis. Here, we assess its role in murine urinary tract infection (UTI) by use of wild-type E. faecalis OG1RF and its nonpiliated, ebpA allelic replacement mutant (TX5475). Methods. OG1RF and TX5475 were administered transurethrally either at an ∼1:1 ratio (competition assay) or individually (monoinfection). Kidney pairs and urinary bladders were cultured 48 h after infection. These strains were also tested in a peritonitis model. Results. No differences were observed in the peritonitis model. In mixed UTIs, OG1RF significantly outnumbered TX5475 in kidneys (P = .0033) and bladders (P ≤ .0001). More OG1RF colony-forming units were also recovered from the kidneys of monoinfected mice at the 4 inocula tested (P = .015 to P = .049), and 50% infective doses of OG1RF for kidneys and bladder (9.1 × 10¹ and 3.5 × 10³ cfu, respectively) were 2-3 log₁₀ lower than those of TX5475. Increased tropism for the kidney relative to the bladder was observed for both OG1RF and TX5475. Conclusion. The ebp locus, part of the core genome of E. faecalis, contributes to infection in an ascending UTI model and is the first such enterococcal locus shown to be important in this site.