We examined 219 Shiga toxin-producing Escherichia coli (STEC) strains from meat, milk, and cheese samples collected in Germany between 2005 and 2006. All strains were investigated for their serotypes and for genetic variants of Shiga toxins 1 and 2 (Stx1 and Stx2). stx 1 or variant genes were detected in 88 (40.2%) strains and stx 2 and variants in 177 (80.8%) strains. Typing of stx genes was performed by stx-specific PCRs and by analysis of restriction fragment length polymorphisms (RFLP) of PCR products. Major genotypes of the Stx1 (stx 1 , stx 1c , and stx 1d ) and the Stx2 (stx 2 , stx 2d , stx 2-O118 , stx 2e , and stx 2g ) families were detected, and multiple types of stx genes coexisted frequently in STEC strains. Only 1.8% of the STEC strains from food belonged to the classical enterohemorrhagic E. coli (EHEC) types O26:H11, O103:H2, and O157:H7, and only 5.0% of the STEC strains from food were positive for the eae gene, which is a virulence trait of classical EHEC. In contrast, 95 (43.4%) of the food-borne STEC strains carried stx 2 and/or mucus-activatable stx 2d genes, an indicator for potential high virulence of STEC for humans. Most of these strains belonged to serotypes associated with severe illness in humans, such as O22:H8, O91:H21, O113:H21, O174:H2, and O174:H21. stx 2 and stx 2d STEC strains were found frequently in milk and beef products. Other stx types were associated more frequently with pork (stx 2e ), lamb, and wildlife meat (stx 1c ). The combination of serotyping and stx genotyping was found useful for identification and for assignment of food-borne STEC to groups with potential lower and higher levels of virulence for humans.

Aims:  To evaluate the suitability of the commercially distributed Ridascreen® Verotoxin enzyme immunoassay (EIA) for detection of known genetic types of the Vero (Shiga) toxins 1 (Stx1) and 2 (Stx2) families and to determine its relative sensitivity and specificity. Methods and Results:  The Ridascreen‐EIA was compared with the Vero cell assay, a P1‐glycoprotein receptor EIA and with stx gene‐specific PCs for detection of Stx with 43 Shiga toxin‐producing strains of Escherichia coli (STEC) reference strains and with 241 test strains. The Ridascreen‐EIA detects strains producing Stx1 and variants Stx1c and Stx1d, as well as Stx2 and variants Stx2d1, Stx2d2, Stx2e, Stx2d, Stx2‐O118 (Stx2d‐ount), Stx2‐NV206, Stx2f and Stx2g. The assay showed a relative sensitivity of 95·7% and a relative specificity of 98·7%. Some of the Stx2‐O118‐, Stx2e‐ and Stx2g‐producing STEC were not detected with the Ridascreen‐EIA probably because of low amount of toxin produced by these strains. Conclusions:  The Ridascreen‐EIA is able to detect all known types of Stx and is applicable for routine screening of bacterial isolates owing to its high specificity. It is less applicable for testing samples where low amounts of Stx are expected, such as mixed cultures and certain Stx2 variants. Significance and Impact of the Study:  This study presents a first comprehensive evaluation of the Ridascreen‐EIA, a rapid standardized STEC screening test for routine diagnostic laboratories. Data are presented on the type of the spectrum of Stx that are detected with this immunoassay and its advantages and limits for practical use.

A total of 140 Shiga toxin-producing Escherichia coli (STEC) strains from wildlife meat (deer, wild boar, and hare) isolated in Germany between 1998 and 2006 were characterized with respect to their serotypes and virulence markers associated with human pathogenicity. The strains grouped into 38 serotypes, but eight O groups (21, 146, 128, 113, 22, 88, 6, and 91) and four H types (21, 28, 2, and 8) accounted for 71.4% and 75.7% of all STEC strains from game, respectively. Eighteen of the serotypes, including enterohemorrhagic E. coli (EHEC) O26:[H11] and O103:H2, were previously found to be associated with human illness. Genes linked to high-level virulence for humans (stx 2 , stx 2d , and eae) were present in 46 (32.8%) STEC strains from game. Fifty-four STEC isolates from game belonged to serotypes which are frequently found in human patients (O103:H2, O26:H11, O113:H21, O91:H21, O128:H2, O146:H21, and O146:H28). These 54 STEC isolates were compared with 101 STEC isolates belonging to the same serotypes isolated from farm animals, from their food products, and from human patients. Within a given serotype, most STEC strains were similar with respect to their stx genotypes and other virulence attributes, regardless of origin. The 155 STEC strains were analyzed for genetic similarity by XbaI pulsed-field gel electrophoresis. O103:H2, O26:H11, O113:H21, O128:H2, and O146:H28 STEC isolates from game were 85 to 100% similar to STEC isolates of the same strains from human patients. By multilocus sequence typing, game EHEC O103:H2 strains were attributed to a clonal lineage associated with hemorrhagic diseases in humans. The results from our study indicate that game animals represent a reservoir for and a potential source of human pathogenic STEC and EHEC strains.Shiga toxin-producing Escherichia coli (STEC) strains represent an important emerging group of food-borne zoonotic pathogens causing diarrhea, hemorrhagic colitis (HC), and the life-threatening hemolytic uremic syndrome (HUS) in humans (30). Production of potent cytotoxins, which are called Shiga toxins (Stx) or Vero toxins (VT) and are encoded on the genomes of temperate lambdoid bacteriophages, is the major virulence determinant of STEC strains. Additional virulence factors, such as genes encoding the attaching and effacing function and virulence plasmid-encoding genes, contribute to the pathogenicity of STEC strains. These virulence genes are closely associated with a subgroup of STEC strains that are frequently isolated from patients with hemorrhagic diseases (HC and HUS) and were therefore designated enterohemorrhagic E. coli (EHEC) strains. Strains belonging to serogroups O157, O26, O103, O111, and O145 are the EHEC types most frequently isolated from humans with HC and HUS (33).STEC strains are part of the gut flora of different animal species, and ruminants, particularly cattle, have been identified as a major reservoir of STEC strains that are highly virulent to humans (27). Today, it is evident that STEC strains can be transmitted from their animal r...

No abstract