Dastmalchi Saei H, Ayremlou N
Department of Microbiology, Faculty of Veterinary Medicine and Department of Cellular and Molecular Biotechnology, Institute of Biotechnology, Urmia University, P.O. Box 1177, Urmia, Iran.
Iran J Microbiol. 2012 Jun;4(2):63-9.
Shiga toxin-producing Escherichia coli (STEC) have emerged as human pathogens and contamination of foods of animal origin has been a major public health concern. The aim of the present study was to determine the dissemination of STEC in healthy and diarrheic calves in Urmia region which is located in West Azerbaijan province, Iran.
In the current study, a total of 124 Escherichia coli isolates from clinically healthy (n = 73) and diarrheic calves (51) belonging to 6 different farms located in West Azerbaijan province, Iran, were screened by the polymerase chain reaction (PCR) assay for the presence of virulence genes characteristic for STEC, that is, Shiga-toxin producing gene(s) (stx1, stx2), intimin (eaeA) and enterohemolysin (hlyA).
STEC isolates were recovered from 21.92% (16/73) in healthy calves, and 19.6% (10/51) in diarrheic calves. Overall, PCR results showed that 6 (23.1%) isolates carried stx1 gene, 7 (26.92%) possessed stx2 gene while 13 isolates (50%) gave positive amplicon both for stx1 and stx2 genes. All stx positive isolates were assayed further to detect eaeA and hlyA sequences. Seven out of the 26 (26.92%) Shiga toxin gene positive isolates were positive for the eaeA gene, and 15 (57.69%) were positive for the hlyA gene. Both virulence genes (eaeA and hlyA) in the same isolate were observed in 5 (19.23%) of the stx(+) isolates. In total, diverse virulence gene profiles were detected, from which isolates with the genetic profile stx1 stx2 hlyA was the most prevalent. In addition, eaeA gene was more evident in isolates from diarrheic calves than in healthy calves.
There was no significant difference in detecting STEC isolates between healthy and diarrheic calves. It seems that calves to be the reservoir of STEC within the herds and calf management may represent specific control points for reducing STEC spread within dairy units.
产志贺毒素大肠杆菌（STEC）已成为人类病原体，动物源性食品的污染一直是主要的公共卫生问题。本研究的目的是确定位于伊朗西阿塞拜疆省乌尔米地区健康和腹泻犊牛中产志贺毒素大肠杆菌的传播情况。
在本研究中，通过聚合酶链反应（PCR）检测对来自伊朗西阿塞拜疆省6个不同农场的124株大肠杆菌分离株进行筛查，这些分离株来自临床健康犊牛（n = 73）和腹泻犊牛（51头），以检测产志贺毒素大肠杆菌特有的毒力基因，即志贺毒素产生基因（stx1、stx2）、紧密黏附素（eaeA）和肠溶血素（hlyA）。
健康犊牛中21.92%（16/73）分离出产志贺毒素大肠杆菌，腹泻犊牛中19.6%（10/51）分离出产志贺毒素大肠杆菌。总体而言，PCR结果显示，6株（23.1%）分离株携带stx1基因，7株（26.92%）拥有stx2基因，而13株（50%）分离株的stx1和stx2基因扩增均呈阳性。对所有stx阳性分离株进一步检测以检测eaeA和hlyA序列。26株（26.92%）志贺毒素基因阳性分离株中有7株eaeA基因呈阳性，15株（57.69%）hlyA基因呈阳性。在5株（19.23%）stx（+）分离株中观察到同一分离株中同时存在两种毒力基因（eaeA和hlyA）。总共检测到多种毒力基因谱，其中基因谱为stx1 stx hlyA的分离株最为普遍。此外，eaeA基因在腹泻犊牛分离株中比在健康犊牛分离株中更明显。
健康犊牛和腹泻犊牛中产志贺毒素大肠杆菌分离株的检测无显著差异。犊牛似乎是畜群中产志贺毒素大肠杆菌的储存宿主，犊牛管理可能是减少乳制品单位内产志贺毒素大肠杆菌传播的特定控制点。
