FimH has a strain and host-cell type dependent role in adherence of E. coli O157:H7 super-shedder strains to host cells

Authors: SREENIDHI, SRINIVASAN - Pennsylvania State University; KATANI, ROBAB - Pennsylvania State University; Kudva, Indira; LI, LINGLING - Pennsylvania State University; Arthur, Terrance; KAPUR, VIVEK - Pennsylvania State University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Escherichia coli O157:H7 (O157) are Shiga toxin-producing food-borne pathogens that are a significant threat to human health, causing severe illnesses including hemorrhagic uremic syndrome and kidney failure. Cattle are the major reservoirs of O157, with asymptomatic animals harboring the organism in their terminal recto-anal junction (RAJ). Some cattle shed greater than or equal to 10**4 CFU of O157/g of feces and are referred to as super-shedders (SS). They are known to play an important role in O157 transmission and prevalence of the disease. Previous work from our lab showed that the SS17 strain of O157 displayed enhanced adherence to bovine rectal cells in a LEE (Locus of Enterocyte Effacement)-independent manner (Cote et al., 2015). We also showed that deletion mutants in SS17 and EDL933 (reference O157 strain) showed alterations in adherence phenotypes on bovine RAJ squamous epithelial (RSE) cells, indicative of strain and host-cell type dependent role of fimH in adherence in both SS17 and EDL933. However, a definitive role for fimH participation in the adherence of O157 strains remained unclear as molecular Koch’s postulates were unfulfilled. Hence, to better understand the role of fimH in O157 adherence phenotype, we constructed a series of fimH complementation strains of SS17 and EDL933 using plasmid complementation (pBBR1MCS) and Lambda red recombination techniques. The results of our studies indicate that for strain SS17, both complementation techniques in SS17 caused a restoration of the wild type phenotype (strong aggregative) on RSE cells, suggesting that, contrary to prevailing dogma, fimH is likely to play a role in the adherence phenotype of O157 strains to specific mammalian cells. In contrast, while complementation of DeltafimH EDL933 using plasmid-encoded fimH restored the adherence phenotype (moderate aggregative), complementation of EDL933 using the recombination method did not. Similarly, the adherence phenotype of both SS17 and EDL933 was restored (to moderate diffuse) on human HEp-2 cells by the plasmid but not by the recombination method. Together, our findings suggest that despite the fim switch being permanently turned “off” in O157, additional genetic elements located in the region encoding fimH likely permit regulatory override of this switch, suggesting the existence of a complexly coordinated regulatory network underlying the expression of fimH in E. coli O157:H7.