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ABSTRACT: Infection with Shiga toxin-producing Escherichia coli (STEC) O157:H7 is characterized by acute inflammation of the colonic mucosa. STEC O157:H7 contains two non-identical loci encoding long polar fimbriae (Lpf), which play a role in the STEC colonization of the intestinal epithelial cells. However, no information is available regarding the involvement of Lpf in the STEC-induced host inflammatory response. Hence, in this study we assess the role of Lpf as an inducer of inflammation on intestinal epithelial cells. Secretion of pro-inflammatory cytokines in response to STEC wild type and lpf isogenic mutants was evaluated on intestinal T84 cells. Of the 27 cytokines assayed, IL-6, IL-8, IL-15, FGF, GM-CSF and IP-10 were significantly reduced, when compared to the wild-type strain, in the lpfA1 lpfA2 double mutant. Further, the host intracellular signaling pathways activated in response to Lpf were determined by using an array containing genes representative of 18 different signal transduction pathways. The analysis indicated that the NF-κB pathway is activated in response to Lpf-expressing STEC. Therefore, our study supports the role of Lpf as a STEC factor mediating intestinal inflammation.
Veterinary Immunology and Immunopathology 09/2012; · 2.08 Impact Factor
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Felipe Del Canto,
Patricio Valenzuela, Lidia Cantero,
Jonathan Bronstein,
Jesús E Blanco,
Jorge Blanco,
Valeria Prado,
Myron Levine,
James Nataro,
Halvor Sommerfelt,
Roberto Vidal
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ABSTRACT: Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea. Three adhesins (Tia, TibA, EtpA), an iron acquisition system (Irp1, Irp2, and FyuA), a GTPase (LeoA), and an autotransporter (EatA) are ETEC virulence-related proteins that, in contrast to the classical virulence factors (enterotoxins and fimbrial colonization factors) have not heretofore been targets in characterizing isolates from epidemiological studies. Here, we determined the occurrence of these nonclassical virulence genes in 103 ETEC isolates from Chilean children with diarrhea and described their association with O serogroups and classical virulence determinants. Because tia, leoA, irp2, and fyuA are harbored by pathogenicity islands inserted into the selC and asnT tRNA genes (tDNAs), we analyzed the regions flanking these loci. Ten additional tDNAs were also screened to identify hot spots for genetic insertions. Associations between the most frequent serogroups and classical colonization factor (CF)-toxin profiles included O6/LT-STh/CS1-CS3-CS21 (i.e., O6 serogroup, heat-labile [LT] and human heat-stable [STh] enterotoxins, and CFs CS1, -3 and -21), O6/LT-STh/CS2-CS3-CS21, and O104-O127/STh/CFAI-CS21. The eatA and etpA genes were detected in more than 70% of the collection, including diverse serogroups and virulence profiles. Sixteen percent of the ETEC strains were negative for classical and nonclassical adhesins, suggesting the presence of unknown determinants of adhesion. The leuX, thrW, and asnT tDNAs were disrupted in more than 65% of strains, suggesting they are hot spots for the insertion of mobile elements. Sequences similar to integrase genes were identified next to the thrW, asnT, pheV, and selC tDNAs. We propose that the eatA and etpA genes should be included in characterizations of ETEC isolates in future epidemiological studies to determine their prevalence in other geographical regions. Sequencing of tDNA-associated genetic insertions might identify new ETEC virulence determinants.
Journal of clinical microbiology 07/2011; 49(9):3198-203. · 4.16 Impact Factor
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ABSTRACT: Adherence to intestinal cells is a key process in infection caused by enterohemorrhagic Escherichia coli (EHEC). Several adhesion factors that mediate the binding of EHEC to intestinal cells have been described, but the receptors involved in their recognition are not fully characterized. Extracellular matrix (ECM) proteins might act as receptors involved in the recognition of enteric pathogens, including EHEC. In this study, we sought to characterize the binding of EHEC O157:H7 to ECM proteins commonly present in the intestine. We found that EHEC prototype strains as well as other clinical isolates adhered more abundantly to surfaces coated with fibronectin, laminin, and collagen IV. Further characterization of this phenotype, by using antiserum raised against the LpfA1 putative major fimbrial subunit and by addition of mannose, showed that a reduced binding of EHEC to ECM proteins was observed in a long polar fimbria (lpf) mutant. We also found that the two regulators, H-NS and Ler, had an effect in EHEC Lpf-mediated binding to ECM, supporting the roles of these tightly regulated fimbriae as adherence factors. Purified Lpf major subunit bound to all of the ECM proteins tested. Finally, increased bacterial adherence was observed when T84 cells, preincubated with ECM proteins, were infected with EHEC. Taken together, these findings suggest that the interaction of Lpf and ECM proteins contributes to the EHEC colonization of the gastrointestinal tract.
Infection and immunity 06/2011; 79(9):3744-50. · 4.21 Impact Factor
