Prevalence of Enterohemorrhagic Escherichia coli O26, O45, O103, O111, O121, O145, and O157 on Hides and Preintervention Carcass Surfaces of Feedlot Cattle at Harvest

Abstract

Cattle hides are a main source of enterohemorrhagic Escherichia coli (EHEC) contamination of beef carcasses. The objectives of this study were to (1) determine the prevalence of "top 6" non-O157 plus O157:H7 EHEC (EHEC-7) on feedlot cattle hides and their matched preintervention carcasses; (2) assess the agreement among detection methods for these matrices; and (3) conduct a molecular risk assessment of EHEC-7 isolates. Samples from 576 feedlot cattle were obtained at a commercial harvest facility and tested for EHEC-7 by a culture-based method and the polymerase chain reaction/mass spectrometry-based NeoSEEK(™) STEC Detection and Identification test (NS). Prevalence data were analyzed with generalized linear mixed models. The cumulative prevalence of EHEC-7 in hide samples as detected by NS was 80.7%, with a distribution of 49.9%, O145; 37.1%, O45; 12.5%, O103; 11.0%, O157; 2.2%, O111; 2.0%, O121; and 0.2%, O26. In contrast, the cumulative prevalence of EHEC-7 in hide samples by culture was 1.2%, with a distribution of 0.6%, O157; 0.4%, O26; 0.2%, O145; and 0%, O45, O103, O111, and O121. The cumulative prevalence of EHEC-7 on matched preintervention carcasses as detected by NS was 6.0%, with a distribution of 2.8%, O157; 1.6%, O145; 1.2%, O103; 1.1%, O45; 0.2%, O26; and 0.0%, O111 and O121. Although the culture-based method detected fewer positive hide samples than NS, it detected EHEC in five hide samples that tested negative for the respective organism by NS. McNemar's chi-square tests indicated significant (p<0.05) disagreement between methods. All EHEC-7 isolates recovered from hides were seropathotype A or B, with compatible virulence gene content. This study indicates that "top 6" and O157:H7 EHEC are present on hides, and to a lesser extent, preintervention carcasses of feedlot cattle at harvest. However, continued improvement in non-O157 detection methods is needed for accurate estimation of prevalence, given the discordant results across protocols.

Prevalence and Level of Enterohemorrhagic Escherichia coli in Culled Dairy Cows at Harvest

“…Hides were rinsed with water by plant employees as part of the routine process before the research team collected samples. Hide and carcass surface samples were collected using wet (35 and 20 ml of buffered peptone water, respectively) Speci-sponges (Nasco, Ft. Atkinson, WI) according to methods previously described (63). Hide samples were collected by swabbing an area of approximately 1,000 cm 2 (32 by 32 cm), 15 cm from the ventral midline near the diaphragm.…”

“…Samples to be quantified were identified based on positive NS or culture results from postenriched samples. Preenriched samples were removed from À808C and allowed to recover at room temperature for 2 h. Using an Eddy Jet 2 spiral plater (IUL Instruments, Königswinter, Germany), 50 ll of the recovered culture was spiral plated on Possé agar that had been modified by reducing the novobiocin (5.0 mg/liter) and potassium tellurite (0.5 mg/liter) (mPossé) as previously described (63), and plates were incubated at 378C for 18 h. Based on the NS results, blue-purple and red-purple colonies were counted for samples positive for EHEC O26, O45, O103, O111, or O157, and bluepurple, red-purple, and green colonies were counted for samples positive for EHEC O121 or O145. EHEC O157 culture-positive samples were spiral plated on CCT-CHROMagar O157, and mauve colonies were enumerated.…”

“…In contrast, culture methods for non-O157 EHEC adulterants have lacked sensitivity and specificity because of the multiplicity of organisms needing to be targeted and the lack of clonality of these organisms, and other than having Shiga toxin and intimin, these organisms lack characteristics that distinguish them from other E. coli (28,38,63,70). FSIS methods for detection and isolation of EHEC from meat products, which involve PCR screening, immunomagnetic separation (IMS), cultural isolation on a chromogenic agar, and confirmatory PCR and agglutination, have been improved through a number of modifications but still are not optimal (67,70).…”

“…To increase sensitivity and specificity, the NeoSEEK STEC Detection and Identification test (NS; Neogen, Lansing, MI) and the Atlas STEC EG2 Combo Detection Assay (Roka Bioscience, Warren, NJ) have been used. The NS test includes a proprietary set of genetic markers, has been approved by the FSIS as a confirmation test for EHEC adulterants in beef trim, and has been used to detect EHEC in veal calf hide samples (72) and feedlot cattle hide and carcass samples (63). The Atlas test has been used on cattle fecal samples (12).…”

“…In one study, the prevalence of EHEC-7 in beef feedlot cattle based on NS test results was 80.7% on hides and 6.0% on preintervention carcass surfaces (63). Culled dairy cows also are a significant source of beef; in 2014, 9.5% of cattle slaughtered were classified as dairy cows (69).…”