137. Streptococcus pyogenes Catabolite Control Protein A (CcpA) Promotes Mucosal Carriage in a Murine Vaginal Colonization Model
Session: Oral Abstract Session: Bacterial Pathogenesis and Virulence
Friday, October 21, 2011: 10:00 AM
Room: 151AB

Background:  Carriage of Streptococcus pyogenes on mucosal surfaces likely maintains a reservoir of the obligate human pathogen within the population.  Factors promoting mucosal carriage are unclear, but may include signals from the host environment (e.g., carbohydrate content) influencing the expression of virulence properties.  The S. pyogenes catabolite control protein A, CcpA, is sensitive to carbohydrate concentration and links this signal through control of transcriptional expression of multiple virulence factors.

Methods:  To investigate the role of CcpA in mucosal carriage, we utilized a novel murine vaginal colonization model with estrogenized C57BL/6 mice inoculated with S. pyogenes of strain HSC5 background.  Total RNA isolated from vaginal washes was used for real-time reverse transcription polymerase chain reaction to compare relative gene expression for a panel of S. pyogenes virulence factors. 

Results:  Carriage duration on murine vaginal mucosa was significantly attenuated in the ccpA- mutant compared to wild-type (median duration of colonization 5 days for ccpA- vs. 32 days for wild-type; Mantel-Cox test p < 0.0001).  Compared to wild-type at 48 hours post-inoculum, the ccpA- mutant exhibited 17.8-fold reduced transcript expression of the SpeB protease (t-test p < 0.01), and 5.3-fold elevated transcript expression of lactate oxidase (LctO) (t-test p < 0.0001), a peroxide producing enzyme.  To determine if elevated LctO activity was possibly limiting mucosal survival, a ccpA-:lctO- double mutant was constructed and found to have significantly prolonged carriage compared to the ccpA- mutant (median colonization 5 days for ccpA- vs. 22 days for ccpA-:lctO-; Mantel-Cox test p = 0.0003).   

Conclusion:  Dysregulation of gene expression in the ccpA- mutant was associated with impaired vaginal mucosal carriage, highlighting the important role of transcriptional regulators in bacterial pathogenesis.  The vaginal colonization model is effective at investigating S. pyogenes carriage and is notable for a relative ease of manipulation of the host tissue environment, and for monitoring of bacterial composition and host inflammatory response.  Further studies are examining the influence of carbohydrate acquisition on mucosal carriage. 


Subject Category: B. Bacterial pathogenesis, studies in animal models, molecular pathogenicity

Michael Watson Jr., M.D., Ph.D., Pediatric Infectious Diseases, Washington University, St. Louis, MO and Michael Caparon, Ph.D., Molecular Microbiology, Washington University, St. Louis, MO

Disclosures:

M. Watson Jr., GlaxoSmithKline: Pediatric Infectious Disease Society Fellowship Award Recipient 2010-2012, Research support and Salary

M. Caparon, None

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