Characterization of enterohemorrhagic Escherichia coli on veal hides and carcasses

Authors: Bosilevac, Joseph - Mick; Wang, Rong; LUEDTKE, BRANDON - University Of Nebraska; HINKLEY, SUSANNE - Geneseek Inc, A Neogen Company; Wheeler, Tommy; KOOHMARAIE, MOHAMMAD - Institute Of Environmental Health Laboratories And Consulting Group

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2016
Publication Date: 1/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5613883
Citation: Bosilevac, J.M., Wang, R., Luedtke, B.E., Hinkley, S., Wheeler, T.L., Koohmaraie, M. 2017. Characterization of enterohemorrhagic Escherichia coli on veal hides and carcasses. Journal of Food Protection. 80(1):136-145. doi:10.4315/0362.028X.JFP-16-247.

Interpretive Summary: In 2012 the USDA Food Safety Inspection Service increased scrutiny of bob veal (calves less than 3 weeks old) and formula-fed veal (calves 20 weeks in age) when a higher percentage of positive tests for Shiga toxin-producing E. coli (STEC) were found in veal compared to beef. To investigate this problem we visited five veal processors and measured the levels and prevalence of E. coli O157:H7 and non-O157 STEC on veal hides and carcasses just after the hide was removed and before any antimicrobial interventions were applied. A year later three of the processors were visited again and similar follow-up samples were collected. Significantly more non-O157 STEC were found on veal hides and carcasses than E. coli O157:H7, as compared to beef where the opposite has been reported. All of the most common STEC groups were found on veal, as were four additional groups not typically tested for. The follow-up samples showed that dressing practices had improved and less STEC was being transferred from hides to carcasses. In addition, a greater proportion of bob veal was found to be contaminated by STEC compared to formula-fed veal, but bob veal were contaminated by different groups of STEC than formula-fed veal.

Technical Abstract: Enterohemorrhagic E. coli (EHEC) are Shiga toxin–producing Escherichia coli (STEC) associated with the most severe forms of foodborne illnesses. The United States Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) has identified a higher percentage of non-O157 EHEC compared to E. coli O157:H7 positive samples collected from veal trimmings than from products produced from other cattle slaughter classes. Eight total sample collections from hides and pre-evisceration carcasses before any antimicrobial interventions were performed at five veal processors to assess E. coli O157:H7 and non-O157 EHEC contamination during bob veal and formula-fed veal dressing procedures. E. coli O157:H7 prevalence was measured by culture isolation and found to be on 20.3% of hides and 6.7% of carcasses. In contrast, a non-O157 EHEC molecular screening assay identified 90.3% of hides and 68.2% of carcasses as positive. Only carcass samples were taken forward to culture confirmation where 38.7% yielded one or more non-O157 EHEC isolates. The recovery of an EHEC varied by plant and sample collection date, ranging from 2.1 to 87.8% among plants and 4.2 to 64.2% within the same plant. Changes made to sanitary dressing procedures between collection times at 3 of the plants significantly reduced hide to carcass transfer of E. coli O157:H7 and non-O157 EHEC. All adulterant EHEC serogroups (O26, O45, O103, O111, O121 and O145) were isolated from veal carcasses as well as four other potentially pathogenic serogroups (O5, O84, O118 and O177). Bob veal was found to have a greater culture prevalence of E. coli O157:H7 and greater positive molecular screens for non-O157 EHEC than formula-fed veal (P < 0.05), but the percentage of culture confirmed non-O157 EHEC were not different (P > 0.05) between the two. EHEC-O26, O111, and O121 were found more often in bob veal (P < 0.05), while EHEC-O103 were found more often in formula-fed veal (P < 0.05).