Abstract
Non-O157 Shiga toxin-producing E. coli (STEC) can cause outbreaks that have great economic and health impact. Since the implementation of STEC screening in Alberta in 2018, it is also essential to have a molecular serotyping method with faster turnaround time for cluster identification and surveillance purposes. This study sought to perform molecular serotyping of the top six non-O157 (O26, O45, O103, O111, O121 and O145) STEC serotypes directly from stools and enrichment broths compared to conventional methods on isolates. Multiplex, serotyping qPCR assays were used to determine sensitivity and specificity of the top six non-O157 STEC serotypes. Sensitivity and specificity were assessed for both singleplex and multiplex qPCR assays for comparison of the top six serotypes. Blinded stool specimens (n = 116) or broth samples (n = 482) submitted from frontline microbiology laboratories for STEC investigation were analyzed by qPCR. Both singleplex and multiplex assays were comparable, and we observed 100% specificity with a limit of detection of 100 colony-forming units per mL. Direct molecular serotyping from stool specimens mostly correlated (88%) with conventional serotyping of the cultured isolate. In cases of discordant serotypes, the top six non-O157 STEC mixed infections were identified and confirmed by culture and conventional serotyping. Detection of non-O157 STEC can be done directly from stool specimens using multiplex PCR assays with the ability to identify mixed infections, which would otherwise remain undetected by conventional serotyping of a single colony. This method can be easily implemented into a frontline diagnostic laboratory to enhance surveillance of non-O157 STEC, as more frontline microbiology laboratories move to culture independent assays.
Highlights
Shiga toxin-producing Escherichia coli (STEC) are one of the major causes of acute gastroenteritis (AGE) in Canada, which may result in complications and hospitalization [1]
AGE caused by STEC can lead to hemolytic uremic syndrome (HUS), a potentially fatal condition resulting in kidney failure
Little data have been published on the incidence of non-O157 infections within Alberta prior to the implementation of routine STEC screening in 2018
Summary
Shiga toxin-producing Escherichia coli (STEC) are one of the major causes of acute gastroenteritis (AGE) in Canada, which may result in complications and hospitalization [1].E. coli O157, one of the most prominent STEC serotypes (synonymous with VerotoxigenicEscherichia coli, VTEC), has been implicated in various food-borne outbreaks world-wide [1].AGE caused by STEC can lead to hemolytic uremic syndrome (HUS), a potentially fatal condition resulting in kidney failure. Shiga toxin-producing Escherichia coli (STEC) are one of the major causes of acute gastroenteritis (AGE) in Canada, which may result in complications and hospitalization [1]. Escherichia coli, VTEC), has been implicated in various food-borne outbreaks world-wide [1]. AGE caused by STEC can lead to hemolytic uremic syndrome (HUS), a potentially fatal condition resulting in kidney failure. HUS is due to the presence of two Shiga toxin virulence factors, encoded stx and stx within the lambdoid prophages that inhibit protein synthesis [2]. The Stx toxin has been shown to be more severe and associated with the development of HUS [3]. STEC require a very low infectious dose (fewer than 100 colony-forming units (CFU/mL)) and have the potential to cause large numbers of outbreaks [4]
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