The objective of this study was to quantify the frequency, distribution, and variability of fecal shedding and super-shedding of Shiga toxin–producing Escherichia coli (STEC) serogroups O26, O45, O103, O111, O121, O145, and O157 in feedlot cattle over time. A total of 750 fecal grab samples were collected over a 5-week period (June–July 2017) from 150 cattle housed in 10 pens at a commercial feedlot operation. Samples were subjected to culture-based methods and real-time quantitative polymerase chain reaction for STEC detection and quantification. Cumulative animal-level prevalence estimates were 9.5%, 5.2%, and 15.8% for STEC O157, non-O157 STEC serogroups only (STEC-6), and for all STEC serogroups tested (STEC-7), respectively, with the prevalence of STEC O157 and STEC-7 significantly differing between weeks (p < 0.01). Most of the variability in fecal shedding for STEC O157, STEC-6, and STEC-7 was between pens, rather than between cattle. Over the 5-week period, 10 animals (6.7%) persistently shed STEC non-O157 over 3 or more consecutive weeks, whereas 2 animals (1.3%) intermittently shed STEC non-O157 on nonconsecutive weeks. Fifteen animals (10.0%) shed multiple STEC serogroups within the same fecal sample and five animals (3.3%) shed multiple serogroups at super-shedding levels, higher than 10⁴ CFU (colony-forming units)/g, in the same sample. The presence of a super-shedder in a pen was significantly associated with a greater within pen-level prevalence of STEC-6 (p = 0.01). This study gives further insights into intermittent and persistent shedding and super-shedding patterns of STEC serogroups in individual feedlot cattle, which can enable the development and effective application of preharvest and periharvest interventions, as well as surveillance strategies, for these pathogens.

中文翻译：

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个体饲养场牛粪便中产志贺毒素大肠杆菌血清群的患病率和浓度的纵向表征

本研究的目的是量化产志贺毒素大肠杆菌的粪便排出和超排出的频率、分布和变异性(STEC) 随着时间的推移，饲养场牛的血清群 O26、O45、O103、O111、O121、O145 和 O157。在 5 周的时间里（2017 年 6 月至 7 月），从商业饲养场操作的 10 个围栏中的 150 头牛中收集了总共 750 份粪便样本。样品经过基于培养的方法和实时定量聚合酶链反应进行 STEC 检测和定量。仅 STEC O157、非 O157 STEC 血清群 (STEC-6) 和所有测试的 STEC 血清群 (STEC-7) 的累积动物水平流行率估计值分别为 9.5%、5.2% 和 15.8%，其中STEC O157 和 STEC-7 在周之间显着不同 ( p < 0.01)。STEC O157、STEC-6 和 STEC-7 粪便排出的大部分变异发生在围栏之间，而不是牛之间。在 5 周期间，10 只动物 (6.7%) 在连续 3 周或更长时间内持续排出 STEC 非 O157，而 2 只动物 (1.3%) 在非连续几周内间歇性排出 STEC 非 O157。15 只动物 (10.0%) 在同一粪便样本中排出多个 STEC 血清群，5 只动物 (3.3%) 在同一样本中以高于 10 ⁴ CFU (菌落形成单位)/g 的超排出水平排出多个血清群。围栏中超级脱落者的存在与围栏内 STEC-6 的较高患病率显着相关（p = 0.01）。本研究进一步深入了解个别饲养场牛中 STEC 血清群的间歇性和持续性脱落和超脱落模式，这可以促进对这些病原体的收获前和收获前干预以及监测策略的开发和有效应用。