U.S. Department of Agriculture, Agriculture Research Service, U.S Meat Animal Research Center, P.O. Box 166, State Spur D, Clay Center, NE 68933, USA.
U.S. Department of Agriculture, Agriculture Research Service, U.S Meat Animal Research Center, P.O. Box 166, State Spur D, Clay Center, NE 68933, USA.
J Food Prot. 2023 Jan;86(1):100031. doi: 10.1016/j.jfp.2022.100031. Epub 2022 Dec 21.
Understanding the dynamics of stress-resistant Escherichia coli (E. coli) across the meat production and processing continuum is important for tracking sources of such microbes and devising effective modes of control. The Locus of Heat Resistance (LHR) is a ∼14-19 Kb genetic element imparting extreme heat resistance (XHR) in Enterobacteriaceae. It has been hypothesized that thermal and antimicrobial interventions applied during meat processing may select for LHRE. coli. Thus, our goal was to study the prevalence and molecular biology of LHRE. coli among lots of beef cattle (n = 3) from production through processing. Two hundred thirty-two generic E. coli isolated from the same animals through seven stages of the beef processing continuum (cattle in feedyards to packaged strip loins) were examined. LHRE. coli were rare (0.6%; 1 of 180) among the early stages of the beef continuum (feces and hides at feedlot, feces and hides at harvest, and preevisceration carcasses), whereas the prevalence of LHRE. coli on final carcasses and strip loins was remarkably higher. Half (14 of 28) of the final carcass E. coli possessed the LHR, while 79.2% (19 of 24) of the strip loin E. coli did. Eighty-five percent (29 of 34) of the LHRE. coli presented with the XHR phenotype. The selection or enrichment of LHRE. coli from harvest steps to the final products appeared unlikely as the LHRE. coli isolates were effectively controlled by antimicrobial interventions typically used during beef processing. Further, whole-genome sequencing of the isolates suggested LHRE. coli are persisting in the chilled processing environment and that horizontal LHR transfer among E. coli isolates may take place.
了解具有抗应激能力的大肠杆菌（E. coli）在肉类生产和加工过程中的动态变化对于追踪此类微生物的来源以及设计有效的控制模式非常重要。耐热基因座（Locus of Heat Resistance，LHR）是一个约 14-19 Kb 的遗传元件，赋予肠杆菌科极端耐热性（extreme heat resistance，XHR）。人们假设，在肉类加工过程中应用的热和抗菌干预措施可能会选择 LHR 的大肠杆菌。因此，我们的目标是研究牛肉生产过程中 LHRE. coli 的流行情况和分子生物学特性。从生产到加工，对 3 批牛（n=3）的 232 株普通大肠杆菌进行了研究。通过牛肉加工连续体的 7 个阶段（牛在饲料场到包装的牛里脊）从同一批动物中分离出 232 株普通大肠杆菌，对其进行了研究。在牛肉连续体的早期阶段（饲料场的粪便和皮毛、收获时的粪便和皮毛以及预屠宰的胴体），LHR 的大肠杆菌很少见（0.6%；180 株中的 1 株），而最终胴体和牛里脊上 LHR 的大肠杆菌的流行率则明显更高。在最终胴体大肠杆菌中，有一半（14 株中的 1 株）携带 LHR，而在牛里脊大肠杆菌中，有 79.2%（24 株中的 19 株）携带 LHR。85%（29 株中的 29 株）的 LHR 的大肠杆菌表现出 XHR 表型。从收获阶段到最终产品，LHR 的大肠杆菌似乎不太可能被选择或富集，因为 LHR 的大肠杆菌在牛肉加工过程中通常使用的抗菌干预措施得到了有效控制。此外，对分离株进行全基因组测序表明，LHR 的大肠杆菌在冷藏加工环境中持续存在，并且 E. coli 分离株之间可能发生水平 LHR 转移。
