Tahamtan Y, Hayati M, Namavari Mm
Razi Vaccine and Serum Research institute Shiraz-Iran.
Iran J Microbiol. 2010 Mar;2(1):8-13.
Shiga toxin-producing Escherichia coli (STEC) strains are human pathogens linked to hemorrhagic colitis and hemolytic uremic syndrome. Shiga toxins (Stx1 and Stx2) are the major virulence factors of these strains. The aim of this work was to study the prevalence and distribution of stx(1) and stx(2) gene in E. coli O157:H7 and non-O157:H7 strains isolated from cattle in Shiraz, Iran.
Four hundred and twenty samples consisted of recto-anal mucosal swabs were collected from cattle. They were checked for the presence of the stx1 and stx2 gene using multiplex-PCR every 1 week over a 1-year period (2007-2008).
A total of 146 strains carrying the stx1 and stx2 gene were isolated from 51 (12.14%) cattle. Overall, 15 (3.57%) were identified as O157:H7 and 131 (31.19%) revealed to be non-O157:H7. Both stx2 and stx1 genes were detected in 51 (34.93%) STEC isolates. Genotypes stx1 and stx2 were detected in 15 (10.27%) and 78 (53.42%) respectively. Seasonal distribution of stx genes revealed high percentage of positive animals in warm seasons. The gene sequence similarity ranged from 94 to 100%.
Frequency of stx1 and stx2 in animals and its relation to human disease is not well understood in Iran. The high prevalence of STEC in cattle seems to parallel that which is usually observed in warm seasons and it also parallels occurrence of human STEC. The higher prevalence of the stx2 gene than stx1 in strain populations isolated from cattle indicates a risk alert of E. coli O157:H7 being shed by cattle in these populations. Appropriate measures are now needed to prevent the spread of this life-threatening foodborne disease in our country.
产志贺毒素大肠杆菌（STEC）菌株是与出血性结肠炎和溶血尿毒综合征相关的人类病原体。志贺毒素（Stx1和Stx2）是这些菌株的主要毒力因子。本研究旨在探讨伊朗设拉子地区牛源大肠杆菌O157:H7和非O157:H7菌株中stx(1)和stx(2)基因的流行情况与分布。
采集420份牛直肠-肛门黏膜拭子样本。在1年时间（2007 - 2008年）内，每隔1周使用多重聚合酶链反应检测stx1和stx2基因的存在情况。
从51头（12.14%）牛中分离出总共146株携带stx1和stx2基因的菌株。总体而言，15株（3.57%）被鉴定为O157:H7，131株（31.19%）被发现是非O157:H7。在51株（34.93%）STEC分离株中检测到stx2和stx1基因。分别在15株（10.27%）和78株（53.42%）中检测到stx1和stx2基因型。stx基因的季节分布显示温暖季节阳性动物的比例较高。基因序列相似性范围为94%至100%。
在伊朗，动物中stx1和stx2的频率及其与人类疾病的关系尚未得到充分了解。牛中STEC的高流行率似乎与温暖季节通常观察到的情况相似，也与人类STEC的发生情况相似。从牛中分离的菌株群体中stx2基因的流行率高于stx1，这表明这些群体中的牛排出大肠杆菌O157:H7存在风险警报。现在需要采取适当措施来预防这种危及生命的食源性疾病在我国的传播。
