Clostridium difficile causes a potentially fatal intestinal disease that is increasing in incidence and severity. These infections are often chronic and incredibly difficult to eradicate. Though this organism presents an enormous public health burden, little is understood about how C. difficile evades host defenses to colonize the human intestine. In order to persist, the bacteria must cope with a continuous onslaught by host defenses. The long-term goal of this project is to reveal how C. difficile evades host innate immunity with the intent of opening new avenues for treatment. The specific objective of this application is to define the mechanisms C. difficile employs to resist cationic antimicrobial peptides (CAMPs) produced by the host. These peptides play a critical role in host innate defenses, preventing the growth and spread of bacteria. Preliminary data obtained thus far indicate that C. difficile can respond and adapt to the presence of CAMPs. I hypothesize that C. difficile has evolved multiple resistance mechanisms that allow the bacterium to bypass host immune responses, such as CAMPs, allowing it to colonize and replicate in the human intestine. This proposal will identify the genetic mechanisms of CAMP resistance in C. difficile, identify and characterize the regulation of CAMP resistance mechanisms, and determine the role of these mechanisms in the virulence and colonization in vivo. CAMP resistance will be studied using traditional genetic and biochemical methods, along with new technologies, such as rapid, whole-genome sequencing. Successful completion of these aims will illuminate fundamental aspects of C. difficile infection and identify potential therapeutic targets for treatment of disease. Furthermore, this knowledge will better our understanding of how host-bacterial interactions in the intestine can lead to digestive diseases. The experiments outlined in this proposal will help me learn a wide range of molecular genetics, biochemistry, and animal research techniques I have not previously used, and also to master methods for use with this important hospital pathogen. Ultimately, this work will set the stage for my future research on C. difficile pathogenesis and provide the framework for my transition into an independent investigator position.

Public Health Relevance

The experiments in this proposal are designed to uncover molecular mechanisms used by C. difficile to subvert host defenses and colonize the intestinal tract. This knowledge will expose potential therapeutic targets for the treatment of digestive disease.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Scientist Development Award - Research & Training (K01)
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Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
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Podskalny, Judith M,
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Emory University
Schools of Medicine
United States
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Liu, Runhui; Suárez, Jose M; Weisblum, Bernard et al. (2014) Synthetic polymers active against Clostridium difficile vegetative cell growth and spore outgrowth. J Am Chem Soc 136:14498-504
Nawrocki, Kathryn L; Crispell, Emily K; McBride, Shonna M (2014) Antimicrobial Peptide Resistance Mechanisms of Gram-Positive Bacteria. Antibiotics (Basel) 3:461-492
Edwards, Adrianne N; McBride, Shonna M (2014) Initiation of sporulation in Clostridium difficile: a twist on the classic model. FEMS Microbiol Lett 358:110-8
Edwards, Adrianne N; Nawrocki, Kathryn L; McBride, Shonna M (2014) Conserved oligopeptide permeases modulate sporulation initiation in Clostridium difficile. Infect Immun 82:4276-91
Edwards, Adrianne N; Suarez, Jose M; McBride, Shonna M (2013) Culturing and maintaining Clostridium difficile in an anaerobic environment. J Vis Exp :e50787
Suarez, Jose M; Edwards, Adrianne N; McBride, Shonna M (2013) The Clostridium difficile cpr locus is regulated by a noncontiguous two-component system in response to type A and B lantibiotics. J Bacteriol 195:2621-31
Purcell, Erin B; McKee, Robert W; McBride, Shonna M et al. (2012) Cyclic diguanylate inversely regulates motility and aggregation in Clostridium difficile. J Bacteriol 194:3307-16