Comparison of Shiga Toxin-Producing Escherichia coli Detection Methods Using Clinical Stool Samples

Abstract

Molecular diagnostic tools capable of identifyingShiga toxin-specific genetic determinants in stool specimens permit an unbiased approach to detect Shiga toxin-producing Escherichia coli (STEC) in clinical samples and can indicate when culture-based isolation methods are required. It is increasingly recognized that clinically relevant STEC are not limited to the singular O157 serotypes , and therefore diagnostic assays targeting toxin-encoding determinants must be able to account for any genetic variation that exists between serotypes. In this study conventional PCR and four real-time PCR assays (HybProbe , TaqMan, SYBR Green, and LUX) targeting the stx1 and stx2 Shiga toxin coding sequences were used to identify STEC in enriched stool samples (n ‫؍‬ 36) and a panel of O157 and non-O157 strains (n ‫؍‬ 64). PCR assays targeting stx1 and stx2 had variable specificity and sensitivity values with enriched stool samples. Molecular assays using DNA from pure cultures revealed that some primers were not sensitive to all stx2 variants. This evaluation concluded that the TaqMan-based probes were most appropriate in high throughput clinical diagnostic laboratories in consideration of cost , turn around time , and assay performance. (J Mol

Comparison of Three Different Methods for Detection of Shiga Toxin-Producing Escherichia coli in a Tertiary Pediatric Care Center

“…In our study, 16 STEC strains were isolated from 8 patients. The difficulty in recovering STEC strains was previously reported by different authors (27,29,36). This may be explained by the freeze-and-thaw effect killing or inhibiting the growth of pathogens.…”

“…Crossreactivity and sensitivity studies were performed with the same panel of organisms and concentrations of O157 STEC used for immunoassays ( Table 2). All positive samples were sent to the Alberta Provincial Public Health Laboratory for confirmation with a real-time PCR assay that used different primers and probes (27).…”

Shiga-Toxigenic Escherichia coli Detection in Stool Samples Screened for Viral Gastroenteritis in Alberta, Canada

“…Oligonucleotide primers and fluorescent probes for stx 1 and stx 2 were described previously (6). The probe for stx 2 was modified from the original (STX2-TM-P) in that the VIC dye was replaced by the 6-carboxyfluorescein (FAM) dye.…”

Survey of verotoxin-producing Escherichia coli and faecal coliforms in beef carcasses destined for export at slaughterhouses in Brazil

“…Another reason for the low prevalence of VTEC may be the difficulty of recovering these isolates, which has already been reported by several authors (Chui et al, 2010(Chui et al, , 2011Pulz et al, 2003). Another hypothesis is a low pathogen's inoculum size, hindering the growth on an agar plate (Vallières et al, 2013).…”