Pooling of Immunomagnetic Separation Beads Does Not Affect Detection Sensitivity of Six Major Serogroups of Shiga Toxin–Producing Escherichia coli in Cattle Feces

Abstract

Shiga toxin-producing Escherichia coli (STEC) of the serogroups O26, O45, O103, O111, O121, and O145, often called non-O157 STEC, are foodborne pathogens. Cattle are asymptomatic reservoirs for STEC; the organisms reside in the hindgut and are shed in the feces, which serve as the source of food product contaminations. Culture-based detection of non-O157 STEC involves an immunomagnetic separation (IMS) step to capture the specific serogroups in complex matrices, such as feces. The IMS procedure is time consuming and labor intensive because of the need to subject each fecal sample to six individual beads. Therefore, our objective was to evaluate whether pooling of IMS beads affects sensitivity of non-O157 STEC detection compared with using individual IMS beads. The evaluation was done by comparing detection of serogroups in feces spiked with pure cultures (experiments 1 and 2) and from feces (n = 384) of naturally shedding cattle (experiment 3). In spiked fecal samples, detection with pools of three, four, six, or seven beads was similar to, or at times higher than, detection with individual IMS beads. In experiment 3, the proportions of fecal samples that tested positive for the six serogroups as detected by individual or pooled beads were similar. Based on noninferiority tests, detection with pooled beads was not substantially inferior to detection with individual beads (P > 0.05). In conclusion, the pooling of IMS beads is a better option for detection of STEC serogroups in fecal samples compared with individual beads because the procedure saves time and labor and has the prospect of a higher throughput.

Enterohaemorrhagic and other Shiga toxin-producingEscherichia coli(STEC): Where are we now regarding diagnostics and control strategies?

“…For IMS, the detection of all major serogroups of STEC requires treating each sample individually with serogroup-specific beads. Such a labour-intensive and time-consuming procedure can now be modified by combining serogroup-specific beads without loss of sensitivity (Noll et al, 2016). The presence of Shiga toxin in faeces is time limited during infection; however, this approach, with or without culture, is often used in suspected cases of HUS to ensure the rapid application of appropriate treatment.…”

“…For IMS, the detection of all major serogroups of STEC requires treating each sample individually with serogroup‐specific beads. Such a labour‐intensive and time‐consuming procedure can now be modified by combining serogroup‐specific beads without loss of sensitivity (Noll et al., ).…”

The future of microbiome analysis: Biosensor methods for big data collection and clinical diagnostics

“…Note: Review articles, as well as articles discussing the telecommunications method OFDM (alternate meaning of "multiplexing"), were excluded via the search terms. Articles were excluded from the timeline if they did not actually demonstrate multiplex detection, or if their detection method was not actually tested with a clinical or field sample et al, Hansbauer et al, 2017;Kraft, Lacher, Shelver, Sherwood, & Bergholz, 2017;Noll et al, 2016Noll et al, , 2018Premaratne et al, 2019;Zhou, Bergeron, & Juncker, 2015). Biosensors are also used to detect offensive molecules in food products, such as contaminants or allergens (Asensi et al, 2009;Bai et al, 2013;Bluhm, Cousin, & Woloshuk, 2004;Bogožalec Košir, Demšar, Štebih, Žel, & Milavec, 2019;X.…”

A sensitive method for the recovery of Escherichia coli serogroup O55 including Shiga toxin‐producing variants for potential use in outbreaks

“…Immuno‐magnetic separation (IMS) can be used for the isolation of E. coli of interest, which may be present in low concentrations, in a sample contaminated with many other bacteria including other E. coli serotypes. Commercially produced magnetic beads are available for O157 and the six most common non‐O157 STEC serogroups (Noll et al ), which can be used for their isolation from food, faeces, water and other environmental samples, where they may be present in low numbers (Lejeune et al ; Islam et al ; Guy et al ; Kanki et al ) (Dynabead product information, https://www.thermofisher.com). The IMS method for the detection of O157 is well established and includes an IMS step followed by plating on selective agar, specifically cefixime‐tellurite sorbitol MacConkey agar (CT‐SMAC).…”