S. aureus is a highly adaptive human pathogen. One result of this adaptation is its ability to develop resistance cationic antimicrobial peptides (CAPs), which are an important part of innate immunity in the hosts. In perusing the S. aureus genomes, we found four two component regulatory systems each of lie adjacent to an ABC transporter system. One of the system, GraRS, regulates the adjacent VraFG efflux system comprising an ATPase and a membrane permease. Mutations in graR or vraG have led to a reduction in resistance to CAPs such as RP-1 (a congener to PMP-1 from platelets) and hNP-1 (from neutrophils), indolicidin and LL37. As an intravascular pathogen, S. aureus likely encounters CAPs from platelets and neutrophils (RP-1 and hNP-1), which we will focus on in this proposal. The exposure of S. aureus to selective CAP has also led to induction of graRS and vraFG and other genes relevant CAP resistance including mprF, dltABCD and also another set of ABC transporter genes vraDE, based on induction studies and microarray analysis. However, the exact contribution of these genes to CAP resistance mediated by GraRS in S. aureus is not defined (Aim I). In addition, in contrast to S. epidermidis where the expression of graRS and vraFG can be induced by any CAPs, the induction in S. aureus is more selective, responding to only a few CAPs. Based on the difference in the sequence of the kinase sensor GraS between S. aureus and S. epidermidis, we propose to define the exact residues within GraS that mediate this recognition of specific CAPs for induction of downstream genes (Aim II). Besides the bacterial factors, we are also interested in the structure of synthetic CAPs and their ability to bind and induce expression of graRS (Aim III). Finally, the in vivo correlate of these finding in GraRS will be explored in a relevant rabbit model of infective endocarditis. Together, these studies will elicit the scientific basis of innate resistance to relevant host CAPs in S. aureus, thus providing a platform to devise strategies to alleviate resistance to cationic antimicrobial peptides.

Public Health Relevance

Innate resistance to cationic antimicrobial peptides in Staphylococcus aureus is part of the armamentarium of this virulent pathogen. This resistance has developed from genes integral to the S. aureus genome and not from externally acquired genes. We have found that genes encoding a two-component regulatory system and the adjacent transporter genes are important for this resistance. We propose to define the mechanism of this resistance. Our long-term goal is to characterize these genes that confer sensitivity to cationic antimicrobial peptides so that we can design better peptide-based antibiotics in the future.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Special Emphasis Panel (ZRG1-IDM-A (02))
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Huntley, Clayton C
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Dartmouth College
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Cheung, Ambrose L; Bayer, Arnold S; Yeaman, Michael R et al. (2014) Site-specific mutation of the sensor kinase GraS in Staphylococcus aureus alters the adaptive response to distinct cationic antimicrobial peptides. Infect Immun 82:5336-45
Abdelhady, Wessam; Bayer, Arnold S; Seidl, Kati et al. (2014) Impact of vancomycin on sarA-mediated biofilm formation: role in persistent endovascular infections due to methicillin-resistant Staphylococcus aureus. J Infect Dis 209:1231-40
Donegan, Niles P; Marvin, Jonathan S; Cheung, Ambrose L (2014) Role of adaptor TrfA and ClpPC in controlling levels of SsrA-tagged proteins and antitoxins in Staphylococcus aureus. J Bacteriol 196:4140-51
Posada, Ana C; Kolar, Stacey L; Dusi, Renata G et al. (2014) Importance of bacillithiol in the oxidative stress response of Staphylococcus aureus. Infect Immun 82:316-32
Yang, Soo-Jin; Bayer, Arnold S; Mishra, Nagendra N et al. (2012) The Staphylococcus aureus two-component regulatory system, GraRS, senses and confers resistance to selected cationic antimicrobial peptides. Infect Immun 80:74-81
Reyes, Dindo; Andrey, Diego O; Monod, Antoinette et al. (2011) Coordinated regulation by AgrA, SarA, and SarR to control agr expression in Staphylococcus aureus. J Bacteriol 193:6020-31
Dumitrescu, Oana; Choudhury, Priya; Boisset, Sandrine et al. (2011) Beta-lactams interfering with PBP1 induce Panton-Valentine leukocidin expression by triggering sarA and rot global regulators of Staphylococcus aureus. Antimicrob Agents Chemother 55:3261-71
Cho, John S; Zussman, Jamie; Donegan, Niles P et al. (2011) Noninvasive in vivo imaging to evaluate immune responses and antimicrobial therapy against Staphylococcus aureus and USA300 MRSA skin infections. J Invest Dermatol 131:907-15