|STROMBERG, ZACHARY - University Of Nebraska|
|LEWIS, GENTRY - University Of Nebraska|
|ALY, SHARIF - University Of California|
|LEHENBAUER, TERRY - University Of California|
|Bosilevac, Joseph - Mick|
|CERNICCHIARO, NATALIA - Kansas State University|
|MOXLEY, RODNEY - University Of Nebraska|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2015
Publication Date: 3/7/2016
Citation: Stromberg, Z.R., Lewis, G.L., Aly, S.S., Lehenbauer, T.W., Bosilevac, J.M., Cernicchiaro, N., Moxley, R.A. 2016. Prevalence and level of enterohemorrhagic Escherichia coli in culled dairy cows at harvest. Journal of Food Protection. 79(3):421-431.
Interpretive Summary: The most common pathogenic E. coli is O157:H7, but there are 6 additional E. coli of concern to public health officials for foodborne illness. E. coli that cause severe disease in humans including bloody diarrhea and kidney failure are called enterohemorrhagic E. coli (EHEC). EHEC can be found in most groups of cattle, but it is not known whether any are specific to culled dairy cows harvested for beef. This study examined matched fecal, hide, and pre-intervention carcass surface samples collected from culled dairy cows at harvest. Three methods were used to identify EHEC in the samples: a culture-based method considered the gold standard, and two commercial test methods. The EHEC prevalence in samples of feces, hides, and carcass surface differed among the test methods used. Culture isolation found EHEC in 6.5% of feces samples, 15.6% of hide samples, and 1.0% of carcass samples. Results from one commercial test moderately agreed with culture results whereas the other commercial test results did not agree with either of the other methods. Detection of an EHEC in feces was associated with the detection of EHEC on the corresponding hide sample. This study provides evidence that EHEC are ubiquitous on the hides of culled dairy cattle, that feces are an important source of EHEC contamination of hides, and that commercial tests for EHEC can provide varying results.
Technical Abstract: The primary objective of this study was to determine the prevalence and concentration of enterohemorrhagic Escherichia coli (EHEC) O26, O45, O103, O111, O121, O145, and O157 (EHEC-7) in fecal, hide, and pre-intervention carcass surface samples from culled dairy cows at harvest. Matched samples were collected from 100 cows at a western U.S. abattoir from June to July 2014, and tested by a culture-based method, NeoSEEK STEC Detection and Identification test (NS), and the Atlas STEC EG2 Combo Detection Assay (Atlas). The EHEC-7 prevalence in samples of feces, hides, and carcass surface, respectively, was 6.5%, 15.6%, and 1.0% by culture, and 25.9%, 64.9%, and 7.0% by NS. By Atlas, the prevalence of non-O157 EHEC was 29.1%, 38.3%, and 28.0% and that of EHEC O157 was 29.1%, 57.0%, and 3.0% for feces, hides, and carcasses, respectively. EHEC-7 were quantifiable in only 1 hide and 1 fecal sample from different cows, and in both cases were EHEC O157 with 5.0 log10 colony-forming units (CFU)/100 cm2 and 3.9 log10 CFU/g in the hide and fecal samples, respectively. EHEC O157 isolates were positive for all virulence genes tested, while non-O157 EHEC contained a lower and variable number of these genes. Moderate agreement was observed between culture and NS for detection of EHEC O26 (Kappa = 0.5773, P < 0.001), EHEC O121 (Kappa = 0.4975, P < 0.001), and EHEC O157 (Kappa = 0.4012, P < 0.001). No significant agreements were observed between NS and Atlas or between culture and Atlas. Detection of an EHEC serogroup in fecal samples was significantly associated with the detection of the corresponding EHEC serogroup on hide samples for EHEC O26 (P = 0.001), EHEC O111 (P = 0.002), EHEC O121 (P < 0.001), and EHEC-6 (P = 0.029) based on NS detection and for EHEC O121 (P < 0.001) based on detection by culture. This study provides evidence that EHEC are ubiquitous on the hides of culled dairy cattle, and that feces are an important source of EHEC contamination of hides.