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Infection and Immunity, November 2007, p. 5399-5404, Vol. 75, No. 11
0019-9567/07/$08.00+0     doi:10.1128/IAI.00663-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Relative Contributions of Enterococcus faecalis OG1RF Sortase-Encoding Genes, srtA and bps (srtC), to Biofilm Formation and a Murine Model of Urinary Tract Infection ^,

Kelvin D. Kemp,^1, Kavindra V. Singh,^1,2, Sreedhar R. Nallapareddy,^1,2, and Barbara E. Murray^1,2,3*

Division of Infectious Diseases, Department of Internal Medicine,¹ Center for the Study of Emerging and Reemerging Pathogens,² Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030³

Received 12 May 2007/ Returned for modification 2 July 2007/ Accepted 17 August 2007

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 srtA bps double mutant showed a much greater reduction (74% versus OG1RF and 44% versus the bps mutant). In a murine urinary tract infection (UTI), the 50% infective doses of both the srtA bps and bps mutants were 2 log₁₀ greater than that of OG1RF or the srtA mutant. Similarly, 2 log₁₀ fewer bacteria were recovered from the kidneys after infection with the bps mutant (P = 0.017) and the srtA bps double mutant (P = 0.022) compared to wild-type strain OG1RF. In a competition UTI, the bps mutant was slightly, but not significantly, less attenuated than the srtA bps 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).

Published ahead of print on 4 September 2007.

Supplemental material for this article may be found at http://iai.asm.org/.

Editor: J. N. Weiser

K.D.K., K.V.S., and S.R.N. contributed equally to this work.

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