Evaluation of the reveal and SafePath rapid Escherichia coli O157 detection tests for use on bovine feces and carcasses

The Reveal (Neogen Corp., Lansing, Mich.) and SafePath (SafePath Laboratori es LLC, St. Paul, Minn.) tests were evaluated for their performance as beef fecal and beef carcass Escherichia coli O157:H7 monitoring tests. Agreemen t between these tests and a reference test system was determined using natu rally contaminated bovine feces and beef carcasses. The reference system ut ilized immunomagnetic separation with plating onto cefixime, tellurite, sor bitol MacConkey agar, followed by colony testing using a serum agglutinatio n test for the O157 antigen. Relative to this reference method, the Reveal test showed a sensitivity of 46% and a specificity of 82% on bovine feces a nd a specificity of 99% on carcass samples. The SafePath test demonstrated a significantly higher sensitivity at 79% and a similar specificity of 79%. On carcass samples the SafePath test performed similarly to the Reveal tes t, demonstrating a specificity of 100% relative to the reference system. Th ere was an insufficient number of E. coli O157-positive carcass samples to estimate precisely the sensitivity of these two methods. Both methods show promise as rapid carcass monitoring tests, but further field testing to est imate sensitivity is needed to complete their evaluation. The proportion of positive fecal samples for E. coli O157:H7 by the reference method ranged from 10.2% to 36% in 10 lots of cattle with an overall mean of 17.3% (39/22 5). Quarter carcass sponging of 125 carcasses revealed 1.6% positive for th e pathogen (2/125).