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In this study we evaluated the performance of the SHIGA TOXIN QUIK CHEK (Techlab®, Blacksburg, VA) and the ImmunoCard STAT! Enterohaemorrhagic E. coli (EHEC) (Meridian BioScience, Cincinnati, OH, USA) assays as methods for qualitatively detecting the presence of Shiga toxin in human fecal specimens. A multiplex PCR for the detection of stx1 and stx2 was used as the standard for comparison. The SHIGA TOXIN QUIK CHEK detected all known Shiga toxin subtypes with the exception of Stx2f, while the ImmunoCard STAT! EHEC was unable to identify four of the seven Stx2 subtypes, including Stx2b and Stx2d. When compared to multiplex PCR based on Shiga toxin gene presence alone both assays demonstrated 100% specificity, and gave sensitivity values of 50.0% and 41.2% respectively. Correlation between each assay and the multiplex PCR was calculated by the use of kappa, with both assays exhibiting a moderate level of agreement., (Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.)

While the differential association of Escherichia coli O157 genotypes with animal and human hosts has recently been well documented, little is known about their distribution between countries and how this might affect regional disease rates. Here, we used a 48-plex single nucleotide polymorphism (SNP) assay to segregate 148 E. coli O157 isolates from Australia, Argentina, and the United States into 11 SNP lineages. We also investigated the relationship between SNP lineages, Shiga toxin (Stx) gene profiles, and total Stx production. E. coli O157 isolates clearly segregated into SNP lineages that were differentially associated with each country. Of the 11 SNP lineages, seven were detected among isolates from a single country, two were detected among isolates from all three countries, and another two were detected only among U.S. and Argentinean isolates. A number of Australian (30%) and Argentinean (14%) isolates were associated with novel, previously undescribed SNP lineages that were unique to each country. Isolates within SNP lineages that were strongly associated with the carriage of stx2a produced comparatively more Stx on average than did those lacking the stx2a subtype. Furthermore, the proportion of isolates in stx2a-associated SNP lineages was significantly higher in Argentina and the United States than Australia (P < 0.05). This study provides evidence for the geographic divergence of E. coli O157 and for a prominent role of stx2a in total Stx production. These results also highlight the need for more comprehensive studies of the global distribution of E. coli O157 lineages and the impacts of regionally predominant E. coli O157 lineages on the prevalence and severity of disease., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Molecular testing for stx1 and/or stx2 is a reliable way of detecting Shiga toxigenic Escherichia coli (STEC) when faecal specimens can be cultured; however, detection of Shiga toxin in unculturable specimens is also of public health importance. The Meridian Premier EHEC assay was evaluated against the gold standard Vero cell cytotoxic assay for Shiga toxin detection in direct faecal specimens. An initial study of 817 patient specimens submitted for routine STEC detection was conducted, evaluating positive faeces detected by the Meridian assay with the Vero cell assay. Twenty-nine percent of 136 Meridian-positive faeces were confirmed as containing Shiga toxin. A further 62 faecal specimens were evaluated for statistical purposes, with all specimens tested by both Meridian and Vero cell assays. On direct faeces, the Meridian assay gave high specificity (76.95%) but low sensitivity (40%). This study confirmed that testing by Meridian assay on cultures is preferential to testing direct faeces for Shiga toxin., (Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.)