|GIRON, JORGE - Universidad De Las Americas, Puebla (MEXICO)|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2016
Publication Date: 10/14/2016
Citation: Kudva, I.T., Carter, M.Q., Sharma, V.K., Stasko, J.A., Giron, J.A. 2016. Curli temper adherence of Escherichia coli O157:H7 to squamous epithelial cells from the bovine recto-anal junction in a strain-dependent manner. Applied and Environmental Microbiology. 83(1):e02594-16. doi: 10.1128/AEM.02594-16.
Interpretive Summary: Cattle are the primary reservoirs of the human pathogen Escherichia coli O157 (O157). Identifying bacterial proteins that help O157 attach to cells at the rectoanal junction in the gastrointestinal tract (GIT) of cattle is important, as this is the site where these bacteria persist the most. Once these proteins have been identified, therapies can be designed to interfere with these attachment proteins with the aim of reducing O157 in cattle. Since the well-characterized O157 adherence protein, intimin, does not contribute to O157 attachment to the squamous cells at the rectoanal junction, we examined another common attachment appendage, curli. We have found that curli, made of the protein curlin, actually tempers the degree of O157 attachment to the squamous cells. Removing, disrupting or interfering with curli results in better O157 attachment to the squamous cells. This is an important observation, which will need to be considered when designing anti-attachment therapies as anything targeting curli may actually result in increased attachment by O157 to cattle GIT.
Technical Abstract: Our recent studies have shown that Intimin and the Locus of Enterocyte Effacement-encoded proteins do not play a role in Escherichia coli O157 (O157) adherence to the bovine recto-anal junction squamous epithelial cells (RSE) cells. Hence, to define factors that play a contributory role, we investigated the role of curli, a fimbrial adhesin implicated in adherence to various fomites, plant, human and animal epithelial cells, in O157 adherence to RSE cells. Specifically, we examined (i) wild-type strains of O157; (ii) curli variants of O157 strains; (iii) isogenic curli-deletion derivatives of O157; and (iv) inhibition of O157 adherence using antisera experimentally generated against this adhesin. Comparison of results of these experiments conducted under stringent conditions with those obtained using HEp2 cells, suggested a modulating role for curli in O157 adherence to RSE cells in contrast to HEp2 cells. Our studies showed that curli did not appear to promote O157 adherence to RSE cells; however, the presence of specific anti-curli antibodies, as well as absence of curli, enhanced O157-RSE interactions, thus alluding to a tempering effect of curli on O157 interactions with these cells. This observation, which is at variance with its reported role in O157 adherence to other cell types, is likely to have implications for development of new anti-adherence modalities.