Detection and Quantification of Seven Major Serogroups of Shiga Toxin-Producing Escherichia coli on Hides of Cull Dairy, Cull Beef, and Fed Beef Cattle at Slaughter

• Published in: Journal of food protection 2018-08, Vol.81 (8), p.1236-1244
• Main Authors: Noll, Lance W, Shridhar, Pragathi B, Ives, Samuel E, Cha, Elva, Nagaraja, T G, Renter, David G
• Format: Article
• Language: English
• Subjects: Abattoirs; Animal populations; Animals; Antigens; Bacteria; Beef; Beef cattle; Bovidae; Cattle; Cattle - microbiology; Contaminants; Contamination; Dairy cattle; Data processing; E coli; Escherichia coli; Feces; Feces - microbiology; Food contamination & poisoning; Food Contamination - analysis; Food Microbiology; Food safety; Humans; Immunomagnetic separation; Laboratories; Methods; Population studies; Potassium; Red Meat - microbiology; Serogroup; Shiga Toxin; Shiga-Toxigenic Escherichia coli - classification; Shiga-Toxigenic Escherichia coli - isolation & purification; Toxins; Virulence
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X.JFP-17-497

Dehiding during beef cattle processing can introduce fecal contaminants, including Shiga toxin-producing Escherichia coli (STEC), from hides onto carcass surfaces, creating the potential for contaminated beef. Fecal shedding of major STEC serogroups (O26, O45, O103, O111, O121, O145, and O157; STEC-7) may differ among cattle populations, yet no study has been conducted to isolate STEC-7 on hides of multiple cattle types on the same production days at the same processing plant. Our objective was to estimate and compare prevalence and concentrations of STEC-7 on hides of cull dairy, cull beef, and fed beef cattle from the same date and processing plant. Overall, 1,500 cattle hides were sponge sampled from cull dairy ( n = 500), cull beef ( n = 500) and fed beef cattle ( n = 500) over 10 processing days. To determine prevalence, samples were subjected to an immunomagnetic separation culture method, and presumptive STEC isolates were tested by PCR for serogroup and major virulence genes. A spiral plate method was used to enumerate STEC-7 from hide samples. Data were analyzed with linear mixed models. All STEC-7 serogroups except O121 were detected and quantified on cattle hides in this study population. Slightly more fed beef hides (77 of 500; 15.4%) and cull beef hides (76 of 500; 15.2%) were positive for at least one STEC-7 strain compared with cull dairy hides (57 of 500; 11.4%), but cattle type was not significantly associated ( P = 0.19) with STEC-7 prevalence. Fed beef hides had a significantly higher prevalence ( P < 0.05) of STEC O103, O145, and O157 serogroups than did either of the other cattle types. The highest proportions of quantifiable samples were for STEC O145 (32 of 1,500 samples; 2.1%) and O157 (31 of 1,500 samples; 2.1%) serogroups, with the majority of concentrations at 3 to 5 and 2 to 4 log CFU/100 cm of hide, respectively. Results indicate that hide contamination with some major STEC serogroups differs significantly among cattle types at harvest, even within the same day and location.