Isolation and Characterization of Shiga Toxin-Producing Escherichia coli Serogroups O26, O45, O103, O111, O113, O121, O145, and O157 Shed from Range and Feedlot Cattle from Postweaning to Slaughter

Abstract

Cattle are the main reservoirs for Shiga toxin-producing Escherichia coli (STEC) strains. E. coli O26, O45, O103, O111, O121, O145, and O157 are among the STEC serogroups that cause severe foodborne illness and have been declared as adulterants by the U.S. Department of Agriculture, Food Safety and Inspection Service. The objectives of this study were (i) to estimate the prevalence of non-O157 STEC and E. coli O157 in naturally infected beef cows and in steer calves at postweaning, during finishing, and at slaughter and (ii) to test non-O157 STEC isolates for the presence of virulence genes stx1, stx2, eaeA, and ehlyA. Samples were collected from study animals during multiple sampling periods and included fecal grabs, rectal swabs, and midline sponge samples. Laboratory culture, PCR, and multiplex PCR were performed to recover and identify E. coli and the virulence genes. The prevalence of non-O157 STEC (serogroups O26, O45, O103, O111, O121, O113, and O145) fecal shedding ranged from 8% (4 of 48 samples) to 39% (15 of 38 samples) in cows and 2% (1 of 47 samples) to 38% (9 of 24 samples) in steer calves. The prevalence of E. coli O157 fecal shedding ranged from 0% (0 of 38 samples) to 52% (25 of 48 samples) in cows and 2% (1 of 47 samples) to 31% (15 of 48 samples) in steer calves. In steer calves, the prevalence of non-O157 STEC and E. coli O157 was highest at postweaning, at 16% (15 of 96 samples) and 23% (22 of 96 samples), respectively. Among the 208 non-O157 STEC isolates, 79% (164 isolates) had stx1, 79% (165 isolates) had stx2, and 58% (121 isolates) had both stx1 and stx2 genes. The percentage of non-O157 STEC isolates encoding the eaeA gene was low; of the 165 isolates tested, 8 (5%) were positive for eaeA and 135 (82%) were positive for ehlyA. Findings from this study provide further evidence of non-O157 STEC shedding in beef cows and steer calves particularly at the stage of postweaning and before entry into the feedlot.

Summer and Winter Prevalence of Shiga Toxin–Producing Escherichia coli (STEC) O26, O45, O103, O111, O121, O145, and O157 in Feces of Feedlot Cattle

“…Although a few studies have addressed the detection of non-O157 STEC in cattle feces, data regarding the frequency of non-O157 STEC serogroups in preharvest cattle in the Unites States are still limited (Cernicchiaro et al, 2013;Dargatz et al, 2013;Baltasar et al, 2014;Ekiri et al, 2014). The prevalence of non-O157 STEC organisms obtained in our study was lower than what has been reported in previous studies (Barkocy-Gallagher et al, 2003;Cernicchiaro et al, 2013;Ekiri et al, 2014) but comparable to others (Cobbold et al, 2004). Different case definitions, study populations, and detection protocols may explain differences in prevalence estimates obtained across studies.…”

“…We hypothesize that serogroup O103 may have different microbial properties allowing the bacterium to endure harsher conditions and outcompete other microbiota, potentially allowing for longer survival in the cattle reservoir and subsequent environment. In another United States study, using similar detection methods, serogroup O103 also was the most frequently isolated non-O157 serogroup among cattle (Ekiri et al, 2014).…”

“…Non-O157 serogroup and STEC fecal prevalence estimates reported in cattle range from 0.0 to 90.7% and 0.9 to 16.9%, respectively, in the United States Cernicchiaro et al, 2013;Dargatz et al, 2013;Baltasar et al, 2014;Ekiri et al, 2014). However, only a few studies have assessed seasonality of non-O157 STEC shedding in cattle (Barkocy-Gallagher et al, 2003;Alexa et al, 2011;Tanaro et al, 2012).…”

Novel sequence types of non-O157 Shiga toxin-producing Escherichia coli isolated from cattle

“…Non‐O157 STEC isolates from cattle faecal samples were collected from the North Dakota State University Research Extension Center at Dickinson, North Dakota, as described previously (Ekiri et al . ). Ekiri et al .…”

Effectiveness of a Commercial Lactic Acid Bacteria Intervention Applied to Inhibit Shiga Toxin-Producing Escherichia coli on Refrigerated Vacuum-Aged Beef

“…The US Department of Agriculture Food Safety and Inspection Service (USDA-FSIS) declared raw nonintact beef, as well as intact beef intended to be processed into nonintact beef, adulterated if found positive for E. coli belonging to serogroups O26, O45, O103, O111, O121, O145, and/or O157 [2]. Cattle serve as a reservoir of STEC [3–5]; eradication of these pathogens from the beef supply chain remains a challenge. Chemical food safety interventions such as lactic acid, peroxyacetic acid, and chlorine are commonly applied to reduce and/or eliminate spoilage and pathogenic organisms from beef surfaces [6–8].…”