Location: Meat Safety & Quality ResearchTitle: Evaluation of rectoanal mucosal swab sampling for molecular detection of Enterohemorrhagic Escherichia coli in beef cattle Author
|Hinkley, Susanne - Geneseek Inc, A Neogen Company|
|Bosilevac, Joseph - Mick|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2016
Publication Date: 3/17/2017
Publication URL: http://handle.nal.usda.gov/10113/5700734
Citation: Agga, G.E., Arthur, T.M., Hinkley, S., Bosilevac, J.M. 2017. Evaluation of rectoanal mucosal swab sampling for molecular detection of Enterohemorrhagic Escherichia coli in beef cattle. Journal of Food Protection. 80(4):661-667. doi:10.4315/0362-028X.JFP-16-435.
Interpretive Summary: Studies of pathogenic Escherichia coli in cattle require large numbers of feces samples to be collected and analyzed. Feces is usually collected by the grab method which is slow and cumbersome. An alternate method uses large foam tipped swabs at the rectum (RAM swabs). RAM swab samples are rapid and simple to collect and target the location of pathogenic E. coli. Determining the presence of pathogenic E. coli requires significant laboratory time and resources to culture them while a rapid molecular method offers results in less time. We compared the presence of pathogenic E. coli in feces collected by grab sample and RAM swabs using a molecular test method that replaces culture and found that RAMS swabs are equal to or better than grab samples for testing of pathogenic E. coli in cattle. These results validate RAM swab sample collection in large and small studies of cattle intended to identify ways to control pathogenic E. coli.
Technical Abstract: Cattle are a primary reservoir of Enterohemorrhagic Escherichia coli (EHEC) and contaminated beef products are a source of human infections. The U.S. Department of Agriculture Food Safety and Inspection Service declared the presence of seven EHEC serogroups (O26, O45, O103, O111, O121, O145 and O157) in raw ground beef as adulterants. Sampling large numbers of animals for EHEC surveillance or evaluations of EHEC focused pre-harvest interventions requires a convenient and robust sampling method. We evaluated the diagnostic performance of rectoanal mucosal swab (RAMS) for the detection of the top seven EHEC serogroups. Paired fecal grab (FG) and RAMS were collected from 176 feedlot cattle and tested using the NeoSEEK STEC confirmation method. The prevalence of virulence-associated genes (stx1, stx2, stx2c, eae and nleB) was higher in RAMS than in FG samples. The two methods had poor agreement, as evaluated by kappa statistics, for the detection of the seven serogroups. Considering their combined results as reference RAMS had higher sensitivity than FG for the detection of O103 (82% vs. 39%), O157 (75% vs. 67%) and O45 (79% vs. 73%) with similar sensitivity for the detection of O145 (67%). O111 and O121 were detected from one and two samples respectively by the FG, and were not detected by RAMS. O26 was not detected by any method. We conclude that RAMS is equivalent or superior to FG sampling for the fecal detection of the top seven EHEC serogroups in feedlot cattle.