Döpfer D, Geue L, de Bree J, de Jong M C M
Quantitative Veterinary Epidemiology Group, Animal Sciences Group of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, the Netherlands.
Prev Vet Med. 2006 Mar 16;73(4):229-40. doi: 10.1016/j.prevetmed.2005.08.024. Epub 2006 Feb 17.
A total of 85 cattle from three German beef farms were followed between birth and slaughter during a period of 2 years and monthly faecal samples were submitted for bacterial culture. Verotoxin-producing Escherichia coli (EC) were detected using a standard diagnostic cascade. Potentially pathogenic VTEC ((p)VTEC) were defined as: positive for (1) verotoxin 1 (vt1) and eae, (2) positive for verotoxin 2 (vt2) and eae, (3) positive for both verotoxins 1 and 2 and eae, while verotoxinogenic EC (EC(vt1,2)) were defined as: (1) positive for vt1, (2) positive for vt2 or (3) positive for both vt1 and vt2. There were 1587 observations (1462 valid) available for the statistical analysis including 6 (0.4%) samples from 6 (7.1%) different animals positive for VTEC O157, 78 (5.3%) pVTEC isolates and 389 (26.6%) EC(vt1,2) isolates. The median day of the study at first detection was 280 days for EC(vt1,2) and 315 days for pVTEC. The median age at first detection was: 121 days for EC(vt1,2) and 215 days for pVTEC. Time series analysis, survival analysis, and stochastic SI models were used to find differences in the population dynamics of EC(vt1,2) and pVTEC. There was a strong farm and age effect for the first detection of EC(vt1,2) and for pVTEC while the seasonal effect was significant for the first EC(vt1,2) detections only. With increasing age at first and all consecutive detections, EC(vt1,2) and pVTEC were detected less frequently. The serotype O157 was found more frequently together with detection of other serotypes of pVTEC in the same sample. The EC(vt1,2) were found more often together with pVTEC. The first EC(vt1,2) were on average found before the first pVTEC's and positive cross-correlations existed between EC(vt1,2) and pVTEC. The critical duration for the shedding period above which the VTEC could propagate themselves on the farms by f.e. transmission between animals was found to be between 8 and 18 sampling intervals of 28 days (224-504 days) for EC(vt1,2), and between 5 and 6 sampling periods of 28 days each (140-168 days) for the pVTEC which is smaller than all critical shedding periods for EC(vt1,2). The reasons for EC(vt1,2) being isolated from faeces earlier than pVTEC are discussed.
在两年时间里，对来自德国三个肉牛养殖场的85头牛从出生到屠宰进行了跟踪，并每月提交粪便样本进行细菌培养。使用标准诊断流程检测产志贺毒素大肠杆菌（EC）。潜在致病性VTEC（(p)VTEC）定义为：（1）志贺毒素1（vt1）和eae呈阳性，（2）志贺毒素2（vt2）和eae呈阳性，（3）志贺毒素1和2以及eae均呈阳性，而产志贺毒素EC（EC(vt1,2)）定义为：（1）vt1呈阳性，（2）vt2呈阳性或（3）vt1和vt2均呈阳性。共有1587次观察结果（1462次有效）可用于统计分析，包括来自6头（7.1%）不同动物的6份（0.4%）样本，这些样本的VTEC O157呈阳性，78份（5.3%）pVTEC分离株和389份（26.6%）EC(vt1,2)分离株。首次检测时研究的中位天数，EC(vt1,2)为280天，pVTEC为315天。首次检测时的中位年龄，EC(vt1,2)为121天，pVTEC为215天。使用时间序列分析、生存分析和随机SI模型来发现EC(vt1,2)和pVTEC种群动态的差异。首次检测到EC(vt1,2)和pVTEC时，存在很强的养殖场和年龄效应，而季节性效应仅在首次检测到EC(vt1,2)时显著。随着首次及所有连续检测时年龄的增加，检测到EC(vt1,2)和pVTEC的频率降低。在同一样本中，O157血清型与其他pVTEC血清型的检测同时出现的频率更高。EC(vt1,2)与pVTEC同时出现的频率更高。首次检测到的EC(vt1,2)平均早于首次检测到的pVTEC，并且EC(vt1,2)和pVTEC之间存在正交叉相关性。发现VTEC能够通过例如动物之间的传播在养殖场中自我繁殖的脱落期的关键持续时间，对于EC(vt1,2)为28天的8至18个采样间隔（224 - 504天），对于pVTEC为每个28天的5至6个采样期（140 - 168天），这比EC(vt1,2)的所有关键脱落期都短。讨论了EC(vt1,2)比pVTEC更早从粪便中分离出来的原因。
