title: Relative contributions of Enterococcus faecalis OG1RF sortase-encoding genes, srtA and bps (srtC), to biofilm formation and a murine model of urinary tract infection.
abstract: Deletion mutants of the two sortase genes of Enterococcus faecalis OG1RF were constructed. srtC (renamed here bps for biofilm and pilus-associated sortase) was previously shown to be necessary for the production of Ebp pili and important for biofilm formation and endocarditis. Here, we report that a srtA deletion mutant showed a small (5%) yet significant (P = 0.037) reduction in biofilm relative to OG1RF, while a DeltasrtA Deltabps double mutant showed a much greater reduction (74% versus OG1RF and 44% versus the Deltabps mutant). In a murine urinary tract infection (UTI), the 50% infective doses of both the DeltasrtA Deltabps and Deltabps mutants were approximately 2 log10 greater than that of OG1RF or the DeltasrtA mutant. Similarly, approximately 2 log10 fewer bacteria were recovered from the kidneys after infection with the Deltabps mutant (P = 0.017) and the DeltasrtA Deltabps double mutant (P = 0.022) compared to wild-type strain OG1RF. In a competition UTI, the Deltabps mutant was slightly, but not significantly, less attenuated than the DeltasrtA Deltabps double mutant. Fluorescence-activated cell sorter analysis with Ebp-specific antibodies confirmed that a minority of OG1RF cells express Ebp pili on their surface in vitro and that Bps has a major role in Ebp pilus biogenesis but also indicated a function for SrtA in surface localization of the pilus subunit protein EbpA. In conclusion, deletion of bps had a major effect on virulence in murine UTIs, as well as biofilm; deletion of srtA from OG1RF had little effect on these phenotypes, but its deletion from a bps mutant had a pronounced effect on biofilm, suggesting that Bps and/or the proteins it anchors may compensate for the loss of some SrtA function(s).
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, 6431 Fannin Street, MSB 2.112, Houston, TX 77030, USA.
authors.forename: Kelvin D
authors.initials: KD
authors.lastname: Kemp
authors.forename: Kavindra V
authors.initials: KV
authors.lastname: Singh
authors.forename: Sreedhar R
authors.initials: SR
authors.lastname: Nallapareddy
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Murray
mesh_terms: D000818:Animals; D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D010861:Fimbriae, Bacterial / Q000502:physiology; D017353:Gene Deletion; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology*; D007668:Kidney / Q000382:microbiology; D051379:Mice; D014552:Urinary Tract Infections / Q000382:microbiology*; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000502:physiology*