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Among US veterans, ST131, primarily its H30 subclone, accounts for most antimicrobial-resistant E. coli and is the dominant E. coli strain overall. Possible contributors include multidrug resistance, extensive virulence gene content, and ongoing transmission. Focused attention to ST131, especially its H30 subclone, could reduce infection-related morbidity, mortality, and costs among veterans.

Adhesion to epithelial cells1 and flagella-mediated motility are critical virulence traits for many Gram-negative pathogens, including enterotoxigenic Escherichia coli (ETEC)2, a major cause of diarrhoea in travellers and children in developing countries3,4. Many flagellated pathogens export putative adhesins belonging to the two-partner secretion (TPS) family5. However, the actual function of these adhesins remains largely undefined. Here we demonstrate that EtpA, a TPS exoprotein adhesin of enterotoxigenic Escherichia coli6, mimics and interacts with highly conserved regions of flagellin, the major subunit of flagella, and that these interactions are critical for adherence and intestinal colonization. Although conserved regions of flagellin are mostly buried in the flagellar shaft7, our results suggest that they are at least transiently exposed at the tips of flagella where they capture EtpA adhesin molecules for presentation to eukaryotic receptors. Similarity of EtpA to molecules encoded by other motile pathogens suggests a potential common paradigm for bacterial adhesion, while participation of conserved regions of flagellin in adherence has implications for development of vaccines for Gram-negative pathogens.

Enterotoxigenic Escherichia coli (ETEC) remains a formidable cause of diarrheal illness worldwide. At present, there is no vaccine that provides broad-based protection against ETEC. A phoA-based self-cloning mutagenesis system, TnphoA.ts, employed to identify novel ETEC surface antigens, led to identification of an ETEC two-partner secretion locus (etpBAC) on the pCS1 virulence plasmid of prototype strain H10407. Cloning and expression of etpBAC in recombinant E. coli LMG194(pJY019) resulted in secretion of a high-molecularweight (HMW) glycosylated exoprotein. This glycoprotein, EtpA, exhibits linear peptide sequence and predicted structural homologies with known HMW adhesins produced by other two-partner secretion loci. Antibodies directed against recombinant EtpA (anti-rEtpA.6H) recognized an HMW protein in culture supernatants of ETEC strains H10407 and LMG194(pJY019) but not in culture supernatant of strain H10407-P, which lacks the 92-kb pCS1 plasmid, or an isogenic etpA mutant. etpA mutants were deficient in adherence to intestinal epithelial cells in vitro, and anti-rEtpA.6H antibodies inhibited association of H10407 with target epithelial cells. Cloning and expression of etpB in recombinant E. coli were sufficient to confer adherence. Screening of multiple ETEC isolates for the etpBAC locus by colony hybridization and by EtpA immunoblotting suggested that EtpA is one of the most common antigens secreted by these pathogens. Together, these results indicate that the newly identified ETEC two-partner secretion locus directs the secretion of a high-molecular-weight glycosylated protein, EtpA, that in concert with the putative EtpB transporter participates in adherence of H10407 to epithelial cells, thereby expanding the repertoire of potential ETEC virulence proteins and vaccine candidates.Enterotoxigenic Escherichia coli (ETEC) remains one of the principal causes of infectious diarrhea in travelers and in children in developing countries (72). ETEC is also an emerging cause of diarrheal illness in industrialized countries, including the United States (3, 6, 75). The organisms belonging to this taxon have genetically diverse E. coli pathotypes characterized by the production of heat-labile enterotoxin and/or heat-stable enterotoxin. In the classic paradigm of ETEC infection, these organisms adhere to the small intestinal mucosa via fimbrial colonization factor (CF) molecules, where they elaborate heatlabile enterotoxin and/or heat-stable enterotoxin. While early studies indicated that immunization with CFs provides protection against ETEC infection, development of a broadly protective vaccine has been hampered by the antigenic heterogeneity of these molecules. However, the recent identification of additional ETEC surface molecules (32,56,68) suggests that the present pathogenesis paradigm is incomplete and consequently that there may be additional antigens that can be exploited in vaccine development.Surface expression of virulence molecules by ETEC and other gram-negative pathogens requires export through t...

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Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease and infant mortality in developing countries. Studies of ETEC pathogenesis relevant to vaccine development have been greatly hampered by the lack of a suitable small-animal model of infection with human ETEC strains. Here, we demonstrate that adult immunocompetent outbred mice can be effectively colonized with the prototypical human ETEC H10407 strain (colonization factor antigen I; heat-labile and heat-stable enterotoxin positive) and that production of heat-labile holotoxin provides a significant advantage in colonization of the small intestine in this model.Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease worldwide. Infections caused by this heterogeneous group of pathogens remain major causes of diarrheal morbidity and infant mortality in developing countries (11,33,61), are perennially associated with disease in travelers (4, 7, 43) and in soldiers deployed to developing countries (8, 32), and have recently been associated with large outbreaks in developed countries, including the United States (1, 13).In the presently accepted paradigm for ETEC pathogenesis, fimbrial (or fibrillar) colonization factors (CFs) (10,22,27) mediate colonization of the small intestine, where organisms elaborate heat-labile enterotoxin (LT) and/or heat-stable enterotoxin (ST) (21, 68). Vaccine development has largely focused on the CFs; however, development of a broadly protective ETEC vaccine has been hampered due to the considerable heterogeneity of the known CFs (6,52,58,62).While a number of other surface antigens of ETEC have been described (20,25,51), their utility as potential vaccine candidates has not been effectively explored, largely due to the lack of a suitable animal model for testing. Animal models that have been used in previous studies of ETEC include infant (3, 16-18, 28, 47) and adult (9) mice, rats (34, 35), and rabbits (19,46,51). All of these models have inherent difficulties in utilization or require anesthesia and/or significant surgical manipulation. Some of the models have not been thoroughly evaluated.We sought to develop a murine model of small-intestinal colonization with human ETEC isolates using adult immunocompetent mice. Here, we report our initial use of this model using the prototypical human ETEC H10407 strain. Furthermore, similar to recent studies of porcine ETEC infection of gnotobiotic piglets (2), we demonstrate that elaboration of the heat-labile toxin provides a distinct advantage to the organism in establishing early colonization of the small-intestinal mucosa.

c Enterotoxigenic Escherichia coli (ETEC) is a major cause of morbidity and mortality due to infectious diarrhea in developing countries for which there is presently no effective vaccine. A central challenge in ETEC vaccinology has been the identification of conserved surface antigens to formulate a broadly protective vaccine. Here, we demonstrate that EatA, an immunogenic secreted serine protease of ETEC, contributes to virulence by degrading MUC2, the major protein present in the small intestinal mucous layer, and that removal of this barrier in vitro accelerates toxin access to the enterocyte surface. In addition, we demonstrate that vaccination with the recombinant secreted passenger domain of EatA (rEatA p ) elicits high titers of antibody and is protective against intestinal infection with ETEC. These findings may have significant implications for development of both subunit and live-attenuated vaccines against ETEC and other enteric pathogens, including Shigella flexneri, that express similar proteins.

dEnterotoxigenic Escherichia coli (ETEC) is a leading cause of death due to diarrheal illness among young children in developing countries, and there is currently no effective vaccine. Many elements of ETEC pathogenesis are still poorly defined. Here we demonstrate that YghJ, a secreted ETEC antigen identified in immunoproteomic studies using convalescent patient sera, is required for efficient access to small intestinal enterocytes and for the optimal delivery of heat-labile toxin (LT). Furthermore, YghJ is a highly conserved metalloprotease that influences intestinal colonization of ETEC by degrading the major mucins in the small intestine, MUC2 and MUC3. Genes encoding YghJ and its cognate type II secretion system (T2SS), which also secretes LT, are highly conserved in ETEC and exist in other enteric pathogens, including other diarrheagenic E. coli and Vibrio cholerae bacteria, suggesting that this mucin-degrading enzyme may represent a shared virulence feature of these important pathogens.