Previous Article | Next Article 
Infection and Immunity, June 2009, p. 2465-2473, Vol. 77, No. 6
0019-9567/09/$08.00+0 doi:10.1128/IAI.01494-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
The Pic Protease of Enteroaggregative Escherichia coli Promotes Intestinal Colonization and Growth in the Presence of Mucin
Susan M. Harrington,1
Jalaluddin Sheikh,1,2
Ian R. Henderson,3
Fernando Ruiz-Perez,2
Paul S. Cohen,4 and
James P. Nataro1,2*
Center for Vaccine Development, University of Maryland School of Medicine, and Departments of Microbiology and Immunology,1 Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201,2 School of Immunity and Infection, University of Birmingham, Birmingham, United Kingdom,3 Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island 028814
Received 8 December 2008/ Returned for modification 8 January 2009/ Accepted 26 March 2009
Enteroaggregative Escherichia coli (EAEC) is increasingly being recognized as a cause of diarrheal disease in diverse populations. No small animal model is currently available to study this pathogen. We report here that conventional mice orally inoculated with prototype EAEC strain 042 generally became colonized, though the abundance of organisms cultured from their stool varied substantially among individual animals. In contrast, mice whose water contained 5 g/liter streptomycin consistently became colonized at high levels (ca. 108 CFU/g of stool). Neither conventional nor streptomycin-treated mice developed clinical signs or histopathologic abnormalities. Using specific mutants in competition with the wild-type strain, we evaluated the contribution of several putative EAEC virulence factors to colonization of streptomycin-treated mice. Our data suggest that the dispersin surface protein and Pic, a serine protease autotransporter secreted by EAEC and Shigella flexneri, promote colonization of the mouse. In contrast, we found no role for the aggregative adherence fimbriae, the transcriptional activator AggR, or the surface factor termed Air (enteroaggregative immunoglobulin repeat protein). To study Pic further, we constructed a single nucleotide mutation in strain 042 which altered only the Pic catalytic serine (strain 042PicS258A). Fractionation of the tissue at 24 h and 3 days demonstrated an approximate 3-log10 difference between 042 and 042PicS258A in the lumen and mucus layer and adherent to tissue. Strains 042 and 042PicS258A adhered similarly to mouse tissue ex vivo. While no growth differences were observed in a continuous-flow anaerobic intestinal simulator system, the wild-type strain exhibited a growth advantage over 042PicS258A in a culture of cecal mucus and in cecal contents in vitro; this difference was manifest only after 6 h of growth. Moreover, enhanced growth of the wild type was observed in comparison with that of the mutant in minimal medium containing mucin but not in the absence of mucin. The data suggest a novel metabolic role for the Pic mucinase in EAEC colonization.
* Corresponding author. Mailing address: University of Maryland, 685 W. Baltimore St., Baltimore, MD 21201. Phone: (410) 706-5328. Fax: (410) 706-6205. E-mail: jnataro{at}medicine.umaryland.edu
Published ahead of print on 6 April 2009.
Infection and Immunity, June 2009, p. 2465-2473, Vol. 77, No. 6
0019-9567/09/$08.00+0 doi:10.1128/IAI.01494-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»