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: Kelvin D Kemp, Kavindra V Singh, Sreedhar R Nallapareddy, Barbara E Murray
• Journal: Infection and immunity (Infect Immun) Vol. 75 Issue 11 Pg. 5399-404 (Nov 2007) ISSN: 0019-9567 [Print] United States
• PMID: 17785477 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Virulence Factors

Topics

• Animals
• Biofilms (growth & development)
• Colony Count, Microbial
• Enterococcus faecalis (enzymology, genetics, growth & development, physiology)
• Fimbriae, Bacterial (physiology)
• Gene Deletion
• Gram-Positive Bacterial Infections (microbiology)
• Kidney (microbiology)
• Mice
• Urinary Tract Infections (microbiology)
• Virulence (genetics)
• Virulence Factors (genetics, physiology)