Sample type and processing plant differences in the proportion of enterohemorrhagic Escherichia coli O157 and non-O157 serogroups in feces and on hides of cull dairy cattle at slaughter

Authors: EDACHE, DAVID - Kansas State University; BEYENE, TARIKU - Kansas State University; BARUCH, JOAQUIN - Kansas State University; SHI, XIAORONG - Kansas State University; SANDERSON, MICHAEL - Kansas State University; NAGARAJA, T.G. - Kansas State University; Smolensky, Dmitriy; CERNICCHIARO, NATALIA - Kansas State University

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2024
Publication Date: 11/7/2024
Citation: Edache, D.O., Beyene, T.J., Baruch, J., Shi, X., Sanderson, M.W., Nagaraja, T., Smolensky, D., Cernicchiaro, N. 2024. Sample type and processing plant differences in the proportion of enterohemorrhagic Escherichia coli O157 and non-O157 serogroups in feces and on hides of cull dairy cattle at slaughter. Foodborne Pathogens and Disease. 21(11):698-707. https://doi.org/10.1089/fpd.2024.0017.
DOI: https://doi.org/10.1089/fpd.2024.0017

Interpretive Summary: Enterohemorrhagic Escherichia coli (EHEC) represent an important group of foodborne bacterial pathogens that cause from mild disease to life-threatening infections in humans. Most of the human related EHEC infections are attributed to ingestion of beef products (particularly undercooked beef), contaminated leafy vegetables, direct contact with cattle or direct/indirect water contamination with cattle feces. However, despite decades of advancement in pre-harvest food safety research focused on the identification of intervention strategies aimed at reducing EHEC pathogens in different cattle population, data regarding hide and fecal prevalence and concentration of EHEC pathogens in cull dairy cattle across seasons and processing plants in the United States (US) is limited or inconsistent. The objectives in this study were threefold: 1) to estimate the prevalence and concentration of EHEC O157 and non-O157 serogroups in fecal and hide samples, 2) identify seasonal and processing plant differences in EHEC prevalence, and 3) assess the association between prevalence of EHEC serogroups in feces and on hides collected from matched cull dairy cattle slaughtered at commercial slaughterhouses in summer and spring months. Approximately 60 fecal (collected directly from the rectum) and 60 hide samples from matched carcasses were collected in the summer of 2017 and spring of 2018 from three different-sized processing plants. Samples were shipped to the pre-harvest food safety laboratory at the College of Veterinary Medicine, Kansas State University for processing and testing. Fecal prevalence was 1.8% and 4.2% for EHEC O157 and EHEC non-O157, respectively, whereas hide prevalence was 3.0% for EHEC O157 and 1.6% for EHEC non-O157. The prevalence of EHEC O157 and non-O157 markedly differed across processing plants and between hides vs. feces, but not between summer and spring months. The association between prevalence of EHEC serogroups in feces with the prevalence on hides collected from matched cattle was 7.8% and 3.8% for EHEC O157 and non-O157, respectively. Taken together, our findings provide evidence of a low prevalence of EHEC serogroups in the feces and on hides of this population of cull dairy cattle, and that their prevalence varies across processing plants. Combining these results with previous studies on the prevalence of Escherichia coli in cattle highlights the need for peri-harvest interventions to reduce the fecal burden of EHEC and should be the continuous focus of research and development in the beef industry to decrease hide and carcass contamination and mitigate subsequent EHEC risk.

Technical Abstract: The study was conducted to determine the prevalence and concentration of enterohemorrhagic Escherichia coli (EHEC) O157 and six non-O157 (O26, O45, O103, O111, O121, and O145) serogroups and identify seasonal and processing plant differences in feces and on hides of cull dairy cattle processed in commercial slaughterhouses in the United States (US). Approximately 60 rectal and 60 hide-on samples from matched carcasses were collected in each of three processing plants, in summer 2017 and spring 2018. Samples before enrichment were spiral plated to quantify EHEC and post-enriched samples underwent culture methods that included immuno-magnetic separation (IMS), plating on selective media, and PCR assays for identification and serogroup confirmation of putative isolates. An isolate was considered EHEC O157 positive if it harbored serogroup-specific, Shiga toxin (stx1 and/or stx2), and intimin (eae) genes; and EHEC non-O157 positive, if at least one of the non-O157 serogroup-specific, stx1 and/or stx2 and eae genes were identified. Generalized linear mixed models were fitted to estimate overall prevalence for EHEC O157 and non-O157 EHEC serogroups as well as seasonal and processing plant differences in fecal and hide-on prevalences. The fecal prevalence at the sample level was 1.8% (95% CI = 0.0-92.2 %) and 4.2% (95% CI = 0.0-100.0%) for EHEC O157 and EHEC non-O157, respectively. Hide sample level prevalence was 3.0% (95% CI = 0.0-99.9%) for EHEC O157 and 1.6% (95% CI = 0.0-100.0%) for EHEC non-O157. The prevalence for EHEC O157 and non-O157 significantly differed by processing plant and sample type (hide vs. feces), but not by season. The association between prevalence of EHEC serogroups in feces with the prevalence on hides collected from matched cattle was 7.8% (95% CI = 0.6-53.3%) and 3.8% % (95% CI = 0.3-30.8%) for EHEC O157 and non-O157, respectively. Taken together, our findings provide evidence of a low prevalence of EHEC serogroups in the feces and on hides of cull dairy cattle, and that their prevalence varies across processing plants.