Cha Wonhee, Fratamico Pina M, Ruth Leah E, Bowman Andrew S, Nolting Jacqueline M, Manning Shannon D, Funk Julie A
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA.
Int J Food Microbiol. 2018 Jan 2;264:8-15. doi: 10.1016/j.ijfoodmicro.2017.10.017. Epub 2017 Oct 21.
Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens, which can cause serious illnesses, including hemorrhagic colitis and hemolytic uremic syndrome. To study the epidemiology of STEC in finishing pigs and examine the potential risks they pose for human STEC infections, we conducted a longitudinal cohort study in three finishing sites. Six cohorts of pigs (2 cohorts/site, 20 pigs/cohort) were randomly selected, and fecal samples (n=898) were collected every two weeks through their finishing period. Eighty-two pigs (68.3%) shed STEC at least once, and the proportion of STEC-positive pigs varied across sites (50-97.5%) and cohorts (15-100%). Clinically important serotypes, O157:H7 (stx, eae) and O26:H11 (stx, eae), were recovered from two pigs at sites C and A, respectively. The most common serotype isolated was O59:H21 (stx), which was particularly prevalent in site B as it was recovered from all STEC positive pigs (n=39). Each cohort showed different patterns of STEC shedding, which were associated with the prevalent serotype. The median shedding duration of STEC in pigs was 28days, consistent with our prior study. However, among pigs shedding O59:H21 at least once, pigs in cohort B2 had a significantly longer shedding duration of 42days (P<0.05) compared to other cohorts. Stx2e was the most commonly observed stx variant in finishing pigs (93.9%), in accordance with the previous studies. Stx2e has been reported to be significantly associated with edema disease in pigs, however, the pathogenicity in humans warrants further investigations. Nonetheless, our findings affirm that pigs are an important reservoir for human STEC infections, and that the circulating serotypes in a cohort and site management factors may significantly affect the prevalence of STEC. Molecular characterization of STEC isolates and epidemiological studies to identify risk factors for shedding in pigs are strongly warranted to further address the significance to public health and to develop mitigation strategies.
产志贺毒素大肠杆菌（STEC）是重要的食源性病原体，可引发包括出血性结肠炎和溶血尿毒综合征在内的严重疾病。为研究育肥猪中STEC的流行病学，并考察其对人类STEC感染构成的潜在风险，我们在三个育肥场开展了一项纵向队列研究。随机选取六组猪（每组20头猪，每个场2组），在其育肥期内每两周采集一次粪便样本（共898份）。82头猪（68.3%）至少有一次排出STEC，STEC阳性猪的比例在不同场（50 - 97.5%）和不同组（15 - 100%）中有所不同。分别在C场和A场的两头猪中检出了具有临床重要性的血清型O157:H7（stx，eae）和O26:H11（stx，eae）。分离出的最常见血清型是O59:H21（stx），在B场尤为普遍，因为从所有STEC阳性猪（n = 39）中都分离出了该血清型。每组猪排出STEC的模式不同，这与流行的血清型有关。猪排出STEC的中位持续时间为28天，与我们之前的研究一致。然而，在至少有一次排出O59:H21的猪中，B2组猪的排出持续时间显著更长，为42天（P < 0.05），与其他组相比。根据之前的研究，Stx2e是育肥猪中最常观察到的stx变体（93.9%）。据报道，Stx2e与猪的水肿病显著相关，然而，其对人类的致病性有待进一步研究。尽管如此，我们的研究结果证实猪是人类STEC感染的重要宿主，并且一个组内流行的血清型和场管理因素可能会显著影响STEC的流行率。强烈需要对STEC分离株进行分子特征分析以及开展流行病学研究以确定猪排出STEC的风险因素，从而进一步阐明其对公共卫生的意义并制定缓解策略。
