Department of Bacteriology, National Veterinary Institute, Uppsala, Sweden.
BMC Vet Res. 2010 Jan 29;6:7. doi: 10.1186/1746-6148-6-7.
Several cases of human infection caused by verotoxin-producing Escherichia coli (VTEC) O157:H7 in Sweden have been connected with cattle farm visits. Between 1996 and 2002, 18 farms were classified as the source of human cases with isolation of EHEC (Enterohaemorrhagic Escherichia coli) after VTEC O157:H7 had been isolated from cattle on those farms.
Characterization by phage typing and molecular methods of the strains isolated from these 18 farms, including PCR for virulence genes (vtx1, vtx2 and variants thereof, eaeA and EHEC-hlyA) and Pulsed-Field Gel Electrophoresis (PFGE), demonstrated a cluster of very similar strains from 16 farms. All were of phage type 4, carried the genes encoding the verotoxins VT2 and VT2c, intimin, EHEC-haemolysin and flagellin H7 as shown by PCR, and had identical or very similar PFGE patterns. When analysing strains in a prevalence study of VTEC O157:H7 from cattle at slaughter as well as from an on-farm prevalence study of dairy cattle, using the same typing methods, a rather wide variation was observed among the isolated VTEC O157:H7 strains.
In Sweden, a limited group of genetically similar and highly pathogenic VTEC O157:H7 strains seem to predominate in direct or indirect transmission from cattle to man.
瑞典发生了几起因产肠毒素大肠杆菌（VTEC）O157：H7 引起的人类感染病例，这些病例都与牛场访问有关。在 1996 年至 2002 年期间，有 18 个农场被归类为人类病例的源头，这些农场的牛群中分离出了 EHEC（肠出血性大肠杆菌），之后分离出了 O157：H7 型 VTEC。
通过噬菌体分型和分子方法对这 18 个农场分离出的菌株进行特征描述，包括针对毒力基因（vtx1、vtx2 及其变体、eaeA 和 EHEC-hlyA）的 PCR 以及脉冲场凝胶电泳（PFGE），结果显示 16 个农场的菌株存在非常相似的簇。所有菌株均为噬菌体 4 型，携带编码 verotoxin VT2 和 VT2c、intimin、EHEC-hemolysin 和 flagellin H7 的基因，PCR 结果显示这些基因均呈阳性，并且 PFGE 图谱相同或非常相似。在对屠宰牛群中的 VTEC O157：H7 流行情况以及对奶牛场进行的流行情况进行研究时，使用相同的分型方法，从分离出的 O157：H7 型 VTEC 菌株中观察到了相当大的变异。
在瑞典，一组数量有限、遗传上相似且具有高致病性的 VTEC O157：H7 菌株似乎在牛群向人类的直接或间接传播中占主导地位。
