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Infection and Immunity, August 2008, p. 3451-3463, Vol. 76, No. 8
0019-9567/08/$08.00+0     doi:10.1128/IAI.00343-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

CcpA-Mediated Repression of Streptolysin S Expression and Virulence in the Group A Streptococcus^,

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9048,¹ Department of Cell Biology and Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, Maryland 20742-4451²

Received 14 March 2008/ Returned for modification 28 April 2008/ Accepted 10 May 2008

CcpA is the global mediator of carbon catabolite repression (CCR) in gram-positive bacteria, and growing evidence from several pathogens, including the group A streptococcus (GAS), suggests that CcpA plays an important role in virulence gene regulation. In this study, a deletion of ccpA in an invasive M1 GAS strain was used to test the contribution of CcpA to pathogenesis in mice. Surprisingly, the ccpA mutant exhibited a dramatic "hypervirulent" phenotype compared to the parental MGAS5005 strain, reflected as increased lethality in a model of systemic infection (intraperitoneal administration) and larger lesion size in a model of skin infection (subcutaneous administration). Expression of ccpA in trans from its native promoter was able to complement both phenotypes, suggesting that CcpA acts to repress virulence in GAS. To identify the CcpA-regulated gene(s) involved, a transcriptome analysis was performed on mid-logarithmic-phase cells grown in rich medium. CcpA was found to primarily repress 6% of the GAS genome (124 genes), including genes involved in sugar metabolism, transcriptional regulation, and virulence. Notably, the entire sag operon necessary for streptolysin S (SLS) production was under CcpA-mediated CCR, as was SLS hemolytic activity. Purified CcpA-His bound specifically to a cre within sagAp, demonstrating direct repression of the operon. Finally, SLS activity is required for the increased virulence of a ccpA mutant during systemic infection but did not affect virulence in a wild-type background. Thus, CcpA acts to repress SLS activity and virulence during systemic infection in mice, revealing an important link between carbon metabolism and GAS pathogenesis.

Published ahead of print on 19 May 2008.

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

Editor: A. Camilli