Paddock Zac D, Renter David G, Cull Charley A, Shi Xiarong, Bai Jianfa, Nagaraja Tiruvoor G
1 Department of Diagnostic Medicine and Pathobiology, Kansas State University , Manhattan, Kansas.
Foodborne Pathog Dis. 2014 Mar;11(3):186-93. doi: 10.1089/fpd.2013.1659. Epub 2013 Nov 28.
Escherichia coli O26 is second only to O157 in causing foodborne, Shiga toxin-producing E. coli (STEC) infections. Our objectives were to determine fecal prevalence and characteristics of E. coli O26 in commercial feedlot cattle (17,148) that were enrolled in a study to evaluate an E. coli O157:H7 siderophore receptor and porin (SRP(®)) vaccine (VAC) and a direct-fed microbial (DFM; 10(6) colony-forming units [CFU]/animal/day of Lactobacillus acidophilus and 10(9) CFU/animal/day of Propionibacterium freudenreichii). Cattle were randomly allocated to 40 pens within 10 complete blocks; pens were randomly assigned to control, VAC, DFM, or VAC+DFM treatments. Vaccine was administered on days 0 and 21, and DFM was fed throughout the study. Pen-floor fecal samples (30/pen) were collected weekly for the last 4 study weeks. Samples were enriched in E. coli broth and subjected to a multiplex polymerase chain reaction (PCR) designed to detect O26-specific wzx gene and four major virulence genes (stx1, stx2, eae, and ehxA) and to a culture-based procedure that involved immunomagnetic separation and plating on MacConkey agar. Ten presumptive E. coli colonies were randomly picked, pooled, and tested by the multiplex PCR. Pooled colonies positive for O26 serogroup were streaked on sorbose MacConkey agar, and 10 randomly picked colonies per sample were tested individually by the multiplex PCR. The overall prevalence of E. coli O26 was higher (p<0.001) by the culture-based method compared to the PCR assay (22.7 versus 10.5%). The interventions (VAC and or DFM) had no impact on fecal shedding of O26. Serogroup O26 was recovered in pure culture from 23.9% (260 of 1089) of O26 PCR-positive pooled colonies. Only 7 of the 260 isolates were positive for the stx gene and 90.1% of the isolates possessed an eaeβ gene that codes for intimin subtype β, but not the bfpA gene, which codes for bundle-forming pilus. Therefore, the majority of the O26 recovered from feedlot cattle feces was atypical enteropathogenic E. coli, and not STEC.
大肠杆菌O26在引起食源性产志贺毒素大肠杆菌（STEC）感染方面仅次于O157。我们的目标是确定参与一项研究的17148头商业饲养场牛中大肠杆菌O26的粪便流行率及其特征，该研究旨在评估一种大肠杆菌O157:H7铁载体受体和孔蛋白（SRP®）疫苗（VAC）以及一种直接投喂微生物（DFM；嗜酸乳杆菌10⁶ 菌落形成单位[CFU]/动物/天和费氏丙酸杆菌10⁹ CFU/动物/天）。牛被随机分配到10个完整区组内的40个围栏中；围栏被随机分配到对照、VAC、DFM或VAC + DFM处理组。疫苗在第0天和第21天接种，DFM在整个研究过程中投喂。在研究的最后4周每周收集围栏地面粪便样本（每个围栏30份）。样本在大肠杆菌肉汤中增菌，并进行多重聚合酶链反应（PCR），该反应旨在检测O26特异性wzx基因和四个主要毒力基因（stx1、stx2、eae和ehxA），还进行基于培养的程序，该程序包括免疫磁珠分离并接种在麦康凯琼脂平板上。随机挑选10个推定的大肠杆菌菌落，合并后用多重PCR检测。O26血清型呈阳性的合并菌落划线接种在山梨糖麦康凯琼脂平板上，每个样本随机挑选10个菌落分别用多重PCR检测。与PCR检测法相比，基于培养的方法检测出的大肠杆菌O26总体流行率更高（p<0.001）（分别为22.7%和10.5%）。干预措施（VAC和/或DFM）对O26的粪便排泄没有影响。从23.9%（1089个中的260个）O26 PCR阳性合并菌落中纯培养物中分离出O26血清型。260株分离株中只有7株stx基因呈阳性，90.1%的分离株具有编码intimin亚型β的eaeβ基因，但不具有编码束状菌毛的bfpA基因。因此，从饲养场牛粪便中分离出的大多数O26是不典型肠致病性大肠杆菌，而非STEC。
