Institute of Meat Hygiene and Technology, Belgrade, Serbia
USDA ARS, U.S. Meat Animal Research Center, Clay Center, Nebraska, USA.
Appl Environ Microbiol. 2020 Dec 17;87(1). doi: 10.1128/AEM.01711-20.
Shiga toxin-producing (STEC) is a foodborne pathogen that has a significant impact on public health, with strains possessing the attachment factor intimin referred to as enterohemorrhagic (EHEC) and associated with life-threatening illnesses. Cattle and beef are considered typical sources of STEC, but their presence in pork products is a growing concern. Therefore, carcasses ( = 1,536) at two U.S. pork processors were sampled once per season at three stages of harvest (poststunning skins, postscald carcasses, and chilled carcasses) and then examined using PCR for Shiga toxin genes (), intimin genes (), aerobic plate count (APC), and counts (EBC). The prevalence of on skins, postscald, and chilled carcasses was 85.3, 17.5, and 5.4%, respectively, with 82.3, 7.8, and 1.7% of swabs, respectively, having and present. All -positive samples were subjected to culture isolation that resulted in 368 STEC and 46 EHEC isolates. The most frequently identified STEC were serogroups O121, O8, and O91 (63, 6.7, and 6.0% of total STEC, respectively). The most frequently isolated EHEC was serotype O157:H7 (63% of total EHEC). Results showed that scalding significantly reduced (0.05) carcass APC and EBC by 3.00- and 2.50-log CFU/100 cm, respectively. A seasonal effect was observed, with STEC prevalence lower (< 0.05) in winter. The data from this study show significant (< 0.05) reduction in the incidence of STEC () from 85.3% to 5.4% and of EHEC ( plus ) from 82.3% to 1.7% within the slaughter-to-chilling continuum, respectively, and that potential EHEC can be confirmed present throughout using culture isolation. Seven serogroups of STEC are responsible for most (>75%) cases of severe illnesses caused by STEC and are considered adulterants of beef. However, some STEC outbreaks have been attributed to pork products, although the same are not considered adulterants in pork because little is known of their prevalence along the pork chain. The significance of the work presented here is that it identifies disease-causing STEC, EHEC, demonstrating that these same organisms are a food safety hazard in pork as well as beef. The results show that most STEC isolated from pork are not likely to cause severe disease in humans and that processes used in pork harvest, such as scalding, offer a significant control point to reduce contamination. The results will assist the pork processing industry and regulatory agencies to optimize interventions to improve the safety of pork products.
产志贺毒素（STEC）的细菌是一种食源性病原体，对公共健康有重大影响，其中携带黏附因子 intimins 的菌株被称为肠出血性（EHEC），并与危及生命的疾病有关。牛和牛肉被认为是 STEC 的典型来源，但猪肉制品中存在 STEC 是一个日益令人关注的问题。因此，在美国的两个猪肉加工厂，每个季节在收获的三个阶段（击晕后剥皮、烫煮后和冷却后）对 1536 个胴体进行一次采样，并使用 PCR 方法对志贺毒素基因（）、黏附素基因（）、需氧平板计数（APC）和大肠埃希菌计数（EBC）进行检测。在剥皮、烫煮后和冷却后的胴体上，的流行率分别为 85.3%、17.5%和 5.4%，相应的拭子分别有 82.3%、7.8%和 1.7%携带 和 。所有阳性样本均进行了培养分离，结果分离出 368 株 STEC 和 46 株 EHEC。最常鉴定出的 STEC 血清群是 O121、O8 和 O91（分别占总 STEC 的 63%、6.7%和 6.0%）。最常分离到的 EHEC 血清型是 O157:H7（占总 EHEC 的 63%）。结果表明，烫煮可使胴体的 APC 和 EBC 分别显著减少（<0.05）3.00-和 2.50-log CFU/100cm。观察到季节性效应，冬季 STEC 的流行率较低（<0.05）。本研究的数据显示，在屠宰到冷却的连续过程中，STEC 的发病率（从 85.3%降至 5.4%）和 EHEC（+）的发病率（从 82.3%降至 1.7%）分别有显著降低（<0.05），并且可以通过培养分离法确认整个过程中都存在潜在的 EHEC。有 7 个 STEC 血清群导致了大多数（>75%）由 STEC 引起的严重疾病，被认为是牛肉的掺杂物。然而，一些 STEC 疫情被归因于猪肉产品，尽管在猪肉中同样的 不被认为是掺杂物，因为人们对其在猪肉链中的流行情况知之甚少。本文工作的意义在于，它鉴定出了引起疾病的 STEC 和 EHEC，表明这些相同的生物体也是猪肉和牛肉食品安全的危害物。结果表明，从猪肉中分离出的大多数 STEC 不太可能导致人类严重疾病，并且在猪肉收获过程中使用的烫煮等工艺为减少污染提供了一个重要的控制节点。研究结果将有助于猪肉加工行业和监管机构优化干预措施，以提高猪肉产品的安全性。
