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首页> 外文期刊>Applied Microbiology >Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States
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Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States

机译：美国纵向研究中奶牛群和农场环境中大肠杆菌毒力因子的动态

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Pathogenic Escherichia coli or its associated virulence factors have been frequently detected in dairy cow manure, milk, and dairy farm environments. However, it is unclear what the long-term dynamics of E. coli virulence factors are and which farm compartments act as reservoirs. This study assessed the occurrence and dynamics of four E. coli virulence factors ( eae , stx _(1), stx _(2), and the gamma allele of the tir gene [γ- tir ]) on three U.S. dairy farms. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. Virulence factors were measured by postenrichment quantitative PCR (qPCR). All factors were detected in most compartments on all farms. Fecal and manure samples showed the highest prevalence, up to 53% for stx and 21% for γ- tir in fecal samples and up to 84% for stx and 44% for γ- tir in manure. Prevalence was low in milk (up to 1.9% for stx and 0.7% for γ- tir ). However, 35% of milk filters were positive for stx and 20% were positive for γ- tir . All factors were detected in feed and water. Factor prevalence and levels, expressed as qPCR cycle threshold categories, fluctuated significantly over time, with no clear seasonal signal independent from year-to-year variability. Levels were correlated between fecal and manure samples, and in some cases autocorrelated, but not between manure and milk filters. Shiga toxins were nearly ubiquitous, and 10 to 18% of the lactating cows were potential shedders of E. coli O157 at least once during their time in the herds. E. coli virulence factors appear to persist in many areas of the farms and therefore contribute to transmission dynamics.
机译：在奶牛粪便，牛奶和奶牛场环境中经常检测到致病性大肠杆菌或其相关毒力因子。但是，尚不清楚大肠杆菌毒力因子的长期动态是什么，以及哪些农场区室充当水库。这项研究评估了三个美国奶牛场中四种大肠杆菌毒力因子（eae，stx_（1），stx_（2）和tir基因[γ-tir]的γ等位基因）的发生和动态。从2004年至2012年收集粪便，粪便，水，饲料，牛奶和牛奶过滤器样品。通过富集后定量PCR（qPCR）测量毒力因子。在所有农场的大多数隔间中都检测到了所有因素。粪便和粪便样本的患病率最高，粪便样本中stx高达53％，γ-tir高达21％，粪便中stx高达84％，γ-tir高达44％。牛奶中的患病率很低（stx和γ-tir分别高达1.9％和0.7％）。但是，35％的牛奶过滤器对stx呈阳性，而20％的γ-tir呈阳性。在饲料和水中检测到所有因素。因子患病率和水平（以qPCR循环阈值类别表示）随时间波动很大，没有明确的季节性信号，与年际变化无关。粪便和粪便样品之间的水平是相关的，在某些情况下是自相关的，粪便和牛奶过滤器之间没有相关性。志贺毒素几乎无处不在，在泌乳牛群中，至少有一次，有10％至18％的泌乳牛是大肠杆菌O157的潜在脱落者。大肠杆菌毒力因子似乎在农场的许多地区仍然存在，因此有助于传播动态。

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