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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.
,
Kavindra V. Singh,1,2,
Sreedhar R. Nallapareddy,1,2,
and
Barbara E. Murray1,2,3*
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/.
K.D.K., K.V.S., and S.R.N. contributed equally to this work.
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