Molecular Profiling of Shiga Toxin-Producing Escherichia coli and Enteropathogenic E. coli Strains Isolated from French Coastal Environments

Abstract

Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains may be responsible for food-borne infections in humans. Twenty-eight STEC and 75 EPEC strains previously isolated from French shellfish-harvesting areas and their watersheds and belonging to 68 distinguishable serotypes were characterized in this study. High-throughput real-time PCR was used to search for the presence of 75 E. coli virulence-associated gene targets, and genes encoding Shiga toxin (stx) and intimin (eae) were subtyped using PCR tests and DNA sequencing, respectively. The results showed a high level of diversity between strains, with 17 unique virulence gene profiles for STEC and 56 for EPEC. Seven STEC and 15 EPEC strains were found to display a large number or a particular combination of genetic markers of virulence and the presence of stx and/or eae variants, suggesting their potential pathogenicity for humans. Among these, an O26:H11 stx 1a eae-␤1 strain was associated with a large number of virulence-associated genes (n ‫؍‬ 47), including genes carried on the locus of enterocyte effacement (LEE) or other pathogenicity islands, such as OI-122, OI-71, OI-43/48, OI-50, OI-57, and the high-pathogenicity island (HPI). One O91:H21 STEC strain containing 4 stx variants (stx 1a , stx 2a , stx 2c , and stx 2d ) was found to possess genes associated with pathogenicity islands OI-122, OI-43/48, and OI-15. Among EPEC strains harboring a large number of virulence genes (n, 34 to 50), eight belonged to serotype O26:H11, O103:H2, O103:H25, O145:H28, O157:H7, or O153:H2. IMPORTANCEThe species E. coli includes a wide variety of strains, some of which may be responsible for severe infections. This study, a molecular risk assessment study of E. coli strains isolated from the coastal environment, was conducted to evaluate the potential risk for shellfish consumers. This report describes the characterization of virulence gene profiles and stx/eae polymorphisms of E. coli isolates and clearly highlights the finding that the majority of strains isolated from coastal environment are potentially weakly pathogenic, while some are likely to be more pathogenic. E scherichia coli is a commensal aerobic bacterium of the warmblooded animal intestinal microbiota and is used as a fecal indicator in the environment to classify shellfish-harvesting and bathing areas (1). However, E. coli can become pathogenic through the acquisition of mobile genetic elements such as bacteriophages, pathogenicity islands, and plasmids. Among pathogenic E. coli strains are the Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains.STEC can cause infections ranging from uncomplicated diarrheas to hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS). Several STEC serotypes have been involved in numerous food-borne outbreaks worldwide (2, 3), and these strains have been identified as enterohemorrhagic E. coli (EHEC). Although E. coli O157:H7 has been the main serotype implicated in HC and HUS since the early ...

High Prevalence of Virulence Genes in Specific Genotypes of Atypical Enteropathogenic Escherichia coli

“…In accordance with previous studies, the positive association between paa and diarrhea was also observed in our study. Balière et al (2016) observed a significantly higher (60%) occurrence of paa in EPEC isolates from environment samples, which is similar to the frequency we observed in raw meat isolates (63.6%) in this study. paa was much more frequently detected in strains isolated from raw meats than from other sources, and was especially higher than strains from healthy carriers (14.8%).…”

“…Several studies have investigated the presence of AT genes in EPEC (Abreu et al, 2013; Balière et al, 2016). In the present study, four AT genes ( ehaC, espP, pet , and pic ) were detected.…”

Isolation and characterisation of Shiga toxin-producing Escherichia coli from Norwegian bivalves

“…All shellfish-harvesting farms are classified as Class A, B or C and this is defined by the E. coli concentrations in the harvested bivalves (Table 1). The sanitary classification of shellfish-harvesting areas in Europe is an important measure that helps to prevent shellfish food-borne outbreaks (Baliere et al, 2016). Table 1.…”

“…Shiga genes are encoded in stx phages. There are many other genes associated with STEC virulence, such as saa, paa, ehaA, iha, sab and more (Baliere et al, 2016), but these are not further discussed here. Two main Shiga toxins have been described:…”

“…The O157:H7 serotype is the predominant serotype implicated in food-borne infections worldwide, and most frequently associated with HUS. E. coli O157:H7 was the first to be described as an STEC and has been implicated in serious diseases since the early 1980s (Baliere et al, 2016). Compared with O157 STEC infections, the identification of non-O157 STEC infections is more complicated and many laboratories typically cannot identify them.…”