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Infection and Immunity, June 2008, p. 2316-2324, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00021-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

EmaA, a Potential Virulence Determinant of Aggregatibacter actinomycetemcomitans in Infective Endocarditis{triangledown}

Gaoyan Tang,1 Todd Kitten,2 Cindy L. Munro,3 George C. Wellman,4 and Keith P. Mintz1*

Department of Microbiology and Molecular Genetics,1 Department of Pharmacology, University of Vermont, Burlington, Vermont 05405,4 The Philips Institute of Oral and Craniofacial Molecular Biology,2 School of Nursing, Virginia Commonwealth University, Richmond, Virginia 232983

Received 7 January 2008/ Returned for modification 27 February 2008/ Accepted 10 March 2008

The gram-negative fastidious human oropharyngeal Aggregatibacter actinomycetemcomitans is implicated in the etiology of infective endocarditis. EmaA, an oligomeric coiled-coil adhesin homologous to YadA of Yersinia enterocolitica, was hypothesized to mediate the interaction of A. actinomycetemcomitans with collagen. Collagen, the most abundant protein in human bodies and the main component of extracellular matrix (ECM), predominates in the supporting tissue of cardiac valves. To extend our earlier studies using purified collagen to determine bacterial binding activities, we developed a tissue model using rabbit cardiac valves to investigate the interaction of A. actinomycetemcomitans with native collagen. The resected mitral valves, with or without removal of the endothelium, were incubated with equivalent numbers of the wild type and the isogenic emaA mutant defective in collagen binding. There was no difference in binding between the wild-type and the mutant strains when the endothelium remained intact. However, the emaA mutant was fivefold less effective than the wild-type strain in colonizing the exposed ECM. A 10-fold increase in the binding of the wild-type strain to ECM was observed compared with the intact endothelium. Similar observations were replicated in an in vivo endocarditis rabbit model; the emaA mutant was 10-fold less effective in the initial infection of the traumatized aortic valve. Colocalization studies indicated that A. actinomycetemcomitans bound to type I collagen. A. actinomycetemcomitans preferentially colonized the ECM and, together with the evidence that EmaA interacts with the native collagen, suggested that the adhesin is likely a potential virulence determinant of the bacterium in the initiation of infective endocarditis.

* Corresponding author. Mailing address: Department of Microbiology and Molecular Genetics, Room 118, Stafford Hall, University of Vermont, 95 Carrigan Drive, Burlington, VT 05405. Phone: (802) 656-0712. Fax: (802) 656-8749. E-mail: Keith.Mintz{at}uvm.edu

{triangledown} Published ahead of print on 17 March 2008.

Editor: A. J. Bäumler

Infection and Immunity, June 2008, p. 2316-2324, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.00021-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Yu, C., Mintz, K. P., Ruiz, T. (2009). Investigation of the Three-Dimensional Architecture of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans by Electron Tomography. J. Bacteriol. 191: 6253-6261 [Abstract] [Full Text]  
  • Gallant, C. V., Sedic, M., Chicoine, E. A., Ruiz, T., Mintz, K. P. (2008). Membrane Morphology and Leukotoxin Secretion Are Associated with a Novel Membrane Protein of Aggregatibacter actinomycetemcomitans. J. Bacteriol. 190: 5972-5980 [Abstract] [Full Text]  


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