Gunn G J, McKendrick I J, Ternent H E, Thomson-Carter F, Foster G, Synge B A
SAC Animal Health Group, Epidemiology Research Unit, Stratherrick Road, Inverness IV2 4JZ, UK.
Vet J. 2007 Nov;174(3):554-64. doi: 10.1016/j.tvjl.2007.08.024. Epub 2007 Oct 31.
The prevalence of verocytotoxin-producing Escherichia coli (VTEC) O157 in 12-30-month-old beef finishing cattle in Scotland was determined using 1g faeces samples enriched in buffered peptone water, followed by immunomagnetic separation (IMS) and isolation on sorbitol MacConkey agar with cefixime and tellurite supplement (CT-SMAC). A validated questionnaire was used to collect information that could be associated with the samples. Generalised Linear Models and Generalised Linear Mixed Models were used to identify factors associated with shedding both between and within groups. A total of 14,856 samples were collected from 952 farms, of which 1231 were positive for VTEC O157. Prevalence levels were calculated with 95% confidence intervals as follows: 7.9% (6.5%, 9.6%) of animals sampled were estimated to be shedding VTEC O157, while 22.8% (19.6%, 26.3%) of farms were estimated as having at least one animal shedding in the group sampled. The median percentage of animals shedding in positive groups was 25% (20%, 32%). An increased probability of a group containing a shedding animal was associated with larger numbers of finishing cattle, the presence of pigs on the farm, or the farm being classed as a dairy unit stocking beef animals. Farms that spread slurry on grazing land were more likely to have shedding animals, while those that spread manure were at lower risk. Groups with older animals were less likely to be identified as positive. There was no significant regional difference in group shedding probabilities, but the proportion of positive groups dropped over two successive years of the study. Higher mean levels of shedding in positive groups were associated with animals being housed rather than at pasture, and this effect was stronger in groups which had recently had a change in housing or diet. Farms with animals at pasture had lower mean prevalence where water was supplied from a natural source, as had farms with higher numbers of finishing cattle. There remained unexplained variability in mean prevalence levels on positive farms in different areas of Scotland.
采用1克粪便样本在缓冲蛋白胨水中富集，随后进行免疫磁珠分离（IMS），并在添加头孢克肟和亚碲酸盐的山梨醇麦康凯琼脂（CT-SMAC）上进行分离，以测定苏格兰12至30月龄育肥牛中产志贺毒素大肠杆菌（VTEC）O157的流行情况。使用经过验证的问卷收集可能与样本相关的信息。采用广义线性模型和广义线性混合模型来识别组间和组内与排菌相关的因素。共从952个农场采集了14,856份样本，其中1231份VTEC O157呈阳性。计算出的流行率及95%置信区间如下：估计所采样动物中有7.9%（6.5%，9.6%）排VTEC O157，而估计22.8%（19.6%，26.3%）的农场在所采样组中至少有一头动物排菌。阳性组中排菌动物的中位数百分比为25%（20%，32%）。含有排菌动物的组的概率增加与育肥牛数量较多、农场有猪或农场被归类为饲养肉牛的奶牛场有关。在放牧地上喷洒粪肥的农场更有可能有排菌动物，而那些施用厩肥的农场风险较低。年龄较大动物的组被鉴定为阳性的可能性较小。组排菌概率在区域上没有显著差异，但在连续两年的研究中阳性组的比例下降。阳性组中较高的平均排菌水平与动物被圈养而非放牧有关，并且这种影响在最近有圈舍或饮食变化的组中更强。有放牧动物的农场，若水源为天然水源，则平均流行率较低，育肥牛数量较多的农场也是如此。苏格兰不同地区阳性农场的平均流行率水平仍存在无法解释的差异。
