A Commensal Gone Bad: Complete Genome Sequence of the Prototypical Enterotoxigenic Escherichia coli Strain H10407

Abstract

In most cases, Escherichia coli exists as a harmless commensal organism, but it may on occasion cause intestinal and/or extraintestinal disease. Enterotoxigenic E. coli (ETEC) is the predominant cause of E. coli-mediated diarrhea in the developing world and is responsible for a significant portion of pediatric deaths. In this study, we determined the complete genomic sequence of E. coli H10407, a prototypical strain of enterotoxigenic E. coli, which reproducibly elicits diarrhea in human volunteer studies. We performed genomic and phylogenetic comparisons with other E. coli strains, revealing that the chromosome is closely related to that of the nonpathogenic commensal strain E. coli HS and to those of the laboratory strains E. coli K-12 and C. Furthermore, these analyses demonstrated that there were no chromosomally encoded factors unique to any sequenced ETEC strains. Comparison of the E. coli H10407 plasmids with those from several ETEC strains revealed that the plasmids had a mosaic structure but that several loci were conserved among ETEC strains. This study provides a genetic context for the vast amount of experimental and epidemiological data that have been published.Current dogma suggests the Gram-negative motile bacterium Escherichia coli colonizes the infant gut within hours of birth and establishes itself as the predominant facultative anaerobe of the colon for the remainder of life (3, 59). While the majority of E. coli strains maintain this harmless existence, some strains have adopted a pathogenic lifestyle. Contemporary tenets suggest that pathogenic strains of E. coli have acquired genetic elements that encode virulence factors and enable the organism to cause disease (12). The large repertoire of virulence factors enables E. coli to cause a variety of clinical manifestations, including intestinal infections mediating diarrhea and extraintestinal infections, such as urinary tract infections, septicemia, and meningitis. Based on clinical manifestation of disease, the repertoire of virulence factors, epidemiology, and phylogenetic profiles, the strains causing intestinal infections can be divided into six separate pathotypes, viz., enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), diffuse adhering E. coli (DAEC), and enterotoxigenic E. coli (ETEC) (33,35,39).ETEC is responsible for the majority of E. coli-mediated cases of human diarrhea worldwide. It is particularly prevalent among children in developing countries, where sanitation and clean supplies of drinking water are inadequate, and in travelers to such regions. It is estimated that there are 200 million incidences of ETEC infection annually, resulting in hundreds of thousands of deaths in children under the age of 5 (55, 64). The essential determinants of ETEC virulence are traditionally considered to be colonization of the host small-intestinal epithelium via plasmid-encoded colonization factors (CFs) and subsequent release of plasmid-encoded heat-stable (ST) ...

Survival in amoeba—a major selection pressure on the presence of bacterial copper and zinc resistance determinants? Identification of a “copper pathogenicity island”

“…E. coli express genes encoding ZntA for Zn 2+ efflux, CopA for Cu + efflux, and the CusCBA complex for periplasmic Cu + efflux, but virulent strains have additional copper resistance systems Senftenberg, or Tennessee isolates (Qin et al 2014). This genetic cluster is comprised of two previously reported metal ion resistance determinants, neither of which was realized until recently to be part of a single contiguous gene cluster (Crossman et al 2010;Hobman and Crossman 2015). One, the pco determinant was first isolated from plasmid pRJ1004 from an Australian pig E. coli isolate (Brown et al 1995) and confers copper resistance.…”

“…Transfer of such plasmids has resulted in a nosocomial outbreak of Klebsiella pneumoniae (Sandegren et al 2012). Moreover, the pco/sil cluster has been identified on pAPEC-O2-R plasmids from avian pathogenic E. coli (Johnson et al 2005), R478 from Serratia marcescens (Gilmour et al 2004), plasmids pK2044 and pLVPK from K. pneumoniae strains (Chen et al 2004;Wu et al 2009), and on the chromosome or plasmids of many pathogenic enteric bacteria such as ETEC H10407 (Crossman et al 2010) and EHEC O104:H4 (Hobman and Crossman The illustrated function of each sil and pco gene product within the operon (Gram-negative) is deduced from homology modeling. The transcription of Pco proteins PcoABCDEFG appears to be regulated by PcoRS (left).…”

Development and Accuracy of Quantitative Real-Time Polymerase Chain Reaction Assays for Detection and Quantification of Enterotoxigenic Escherichia coli (ETEC) Heat Labile and Heat Stable Toxin Genes in Travelers' Diarrhea Samples

“…Both of these plasmids belong to the IncFII incompatibility group. 5 The strain also carries two smaller plasmids, pETEC58 and pETEC52 that are not believed to be associated with toxigenesis. 5 Current clinical diagnostic methods for detection of ETEC in stool include polymerase chain reaction (PCR) and DNA hybridization assays.…”

“…5 The strain also carries two smaller plasmids, pETEC58 and pETEC52 that are not believed to be associated with toxigenesis. 5 Current clinical diagnostic methods for detection of ETEC in stool include polymerase chain reaction (PCR) and DNA hybridization assays. The PCR assays range from conventional multiplex assays to real-time quantitative PCR (qPCR) assays with limits of detection ranging from 1,000 to 10 7 ETEC colony-forming units (CFU)/mL.…”

“…4 The strain has been extensively studied, and its chromosome and plasmids have been sequenced. 5 H10407 carries two toxigenic plasmids, pETEC666, a 66.6 kb plasmid that carries the LT operon eltAB plus an allele of ST, designated sta1, and pETEC948, a 94.8 kb plasmid, that carries a second ST allele, sta2. Both of these plasmids belong to the IncFII incompatibility group.…”