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Immunomagnetic separation used with culture based methods has been a useful technique in the detection of pathogens. However, previous studies have not answered many of the necessary questions for real world applications. The objective of this study was to assess the efficacy of different immunomagnetic separation (IMS) bead types in recovery of the correct serogroup from a mixture of big six non-O157 Shiga toxin-producing Escherichia coli strains. To determine the impact of different matrices on recovery, samples of sterile phosphate buffered saline (PBS), sterile and non-sterile cattle faeces, ground beef and lettuce were inoculated with 10 CFU per ml mixture of isolates representing the six serogroups. After a 6 h incubation at 37°C, samples were mixed with IMS beads from three different commercial sources and plated on eosin methylene blue agar (EMB). Three suspect E. coli colonies were selected from each EMB plate and multiplex polymerase chain reaction was used to determine the serogroup. The rate of correct identification varied with the serogroup, IMS bead manufacturer and matrix. Overall, recovery of the correct serogroup became less likely with increase in matrix complexity, with enrichments containing lettuce having the greatest number of bead types with significantly lower likelihood of correct recovery compared to recovery in PBS. Significance and Impact of the Study The need to accurately and efficiently detect Shiga toxin-producing Escherichia coli (STEC) O26, O45, O103, O111, O121 and O145, which have caused outbreaks on numerous occasions, is a major public health and food safety concern in the United States. Detecting these STEC serogroups can be challenging because methods to detect non-O157 serogroups have not been refined as compared to those for O157. Immunomagnetic separation (IMS) has the potential to isolate STEC from a mixture in complex matrices. Our results highlight the need for optimization of IMS-based detection of STEC to effectively recover the targeted serogroup from a variety of sample matrices.

The objective of this study was to assess the genetic diversity of non-O157Shiga toxin-producing Escherichia coli (STEC) isolates from cattle. Multi-locussequence typing (MLST) was used to identify and compare the sequence types(STs) of 43 non-O157 STEC cattle isolates using the EcMLST database curatedby the STEC Center at Michigan State University. For the 43 isolates, 19 STswere identified and 10 of those STs were novel compared to those in EcMLST.For the 43 isolates, 19 different serotypes were identified. STEC O22:H8, O174:H28 and O8:H19 were most common, and STEC O8 isolates were the mostdiverse, with seven different STs for isolates with that O group. STEC strainswith O types identified in this study have been isolated from cattle by otherresearchers, as well as from cases of human gastroenteritis. Of the 10 novel STsidentified, six were found to be closely related to previously identified STs,indicating that populations of non-O157 STEC in cattle are similar to thosefrom other sources, including human clinical cases.IntroductionShiga toxin-producing Escherichia coli (STEC), alsoknown as Vero toxin-producing E. coli (VTEC), arehuman pathogens of zoonotic origin which have beenlinked to serious disease such as haemorrhagic colitis andhaemolytic uremic syndrome (Smith et al. 2014). Over400 serotypes of STEC/VTEC are identified to be patho-genic due to the presence of one or more genes encodingShiga toxin (Blanco et al. 2004a,b; Brooks et al. 2005;Hussein 2007; Tozzoli and Scheutz 2014). The most stud-ied serotype of STEC to date has been O157:H7, due tolarge outbreaks in the 1980s and 1990s associated withstrains of this serotype (Goldwater and Bettelheim 1998).The importance of non-O157 STEC serotypes has beenincreasingly recognized, and the most recent estimatesfrom the US Centers for Disease Control and Preventionindicate that non-O157 STEC are responsible for themajority of human illness caused by STEC (Scallan et al.2011). Surveillance data of foodborne outbreaks in theUnited States from 1998 to 2008 report that 308 out-breaks during this period were linked to STEC, and ofthose outbreaks that could be attributed to a specific foodsource, 78 were linked to beef (Gould et al. 2013).Cattle are considered to be the main reservoir of STEC,and either directly or indirectly contribute to the presenceof STEC in the food supply. The prevalence of STECO157 in cattle can range from 0 3to27 3%, and dependson a number of factors such as feed type and season(Hussein 2007). The prevalence of non-O157 STEC in

Aims There are several biological characteristics that differ between Escherichia coli O157:H7, a dangerous food-borne pathogen, and the other serotypes of E. coli. Methods and results The optimal growth temperatures (T(opt)) were determined for 32 E. coli strains, whether each strain belonged to the O157 serotype or not. The mean values of T(opt) for the O157 and non-O157 groups were 40.2 and 41.2 degrees C, respectively. Significance and impact of the study This difference is statistically significant (P=0.0002) but has no biological implication.

Aims: To review and characterize the enrichment protocols used for detecting all Shiga-Toxin producing Escherichia coli (STEC) from different matrices. Methods and Results: Firstly, the frequency distribution of the factors characterizing the enrichment protocols is described; secondly, a multiple correspondence analysis is performed to display profiles of association of these factors, and thirdly, published results concerning the relative performances of the protocols are summarized. Trypticase Soy Broth (TSB) is reported as the most frequently used enrichment broth. More often, one antibiotic is added in enrichment broths and these broths are incubated for a duration of 16–24 h at 35–37°C. It also appears that the incubation temperature does not seem to be related to the type of serogroup looked for and that antibiotics are used regardless of the matrix analysed. Finally, results relating to the enrichment protocol efficacy are rare and differ from one study to another. Conclusions: Statistical studies must be conducted so as to assess the efficacy of the main enrichment protocols investigated in this study. Significance and Impact of the Study: This study reviews the most commonly used enrichment protocols and highlights the lack of results as to their relative efficacy.

Aims: To examine the effect of temperature on the antimicrobial efficacy of lactate and propionate against O157 and non-O157 Escherichia coli isolates. Methods and Results: Lactate and, to a lesser extent, propionate effectively reduced viability at 37 °C. Ethanol enhanced this effect. Reducing the temperature to 20 or 5 °C caused an increase in survival in the presence of these organic acids with or without ethanol. At 20 °C the ΔpH, membrane potential and intracellular lactate anion concentration were less than at 37 °C. Conclusions: The efficacy of lactate and propionate against E. coli O157 and non-O157 isolates is reduced at lower temperatures, perhaps due to the reduction in the ΔpH, membrane potential and intracellular lactate anion concentration. Significance and Impact of the Study: These findings suggest that the usefulness of organic acids as decontaminants for E. coli O157 is temperature dependent.