Singh M, Sanyal S C, Yadav J N
Division of Microbiology, Central Drug Research Institute, Lucknow, India.
J Trop Med Hyg. 1992 Oct;95(5):316-21.
A study was undertaken to determine how widely drug resistant enterotoxigenic plasmids are distributed among the animal isolates of Escherichia coli, and their potential for exchange. Thirty-one strains of E. coli isolated from metritis, septicaemia and diarrhoea of animals were tested for the production of enterotoxins. Thirteen strains were enterotoxin producers. Five produced heat-stable enterotoxins (ST), four heat-labile (LT) and four strains produced both (LT/ST) types of enterotoxins. Most of the enterotoxin producing E. coli strains were isolated from diarrhoeal sources, followed by septicaemia and metritis. Of the 13 enterotoxigenic E. coli, nine were resistant to various antibiotics which transferred their drug resistance partially or completely into an E. coli K-12 recipient. Only one strain of serogroup 032, isolated from equine metritis, transferred ampicillin, oxytetracycline and doxycycline resistance and heat-labile enterotoxin biosynthesis determinants en bloc. Plasmid DNA analysis of the exconjugants showed the presence of a 41.8 MDa conjugative plasmid. The presence of such autotransferable enterotoxin biosynthesis replicons in their unusual ecological niches such as metritis and septicaemia suggests the ubiquitous nature of enterotoxin genes which perhaps were selected and spread due to the presence of genes for drug resistance. The potential of cross-infection of human beings from animals and vice versa via such plasmids is discussed.
开展了一项研究，以确定耐药性产肠毒素质粒在动物源大肠杆菌分离株中的分布范围及其交换潜力。对从动物子宫炎、败血症和腹泻中分离出的31株大肠杆菌进行了肠毒素产生检测。13株为肠毒素产生菌。5株产生耐热肠毒素（ST），4株产生不耐热肠毒素（LT），4株同时产生两种（LT/ST）类型的肠毒素。大多数产肠毒素大肠杆菌菌株分离自腹泻源，其次是败血症和子宫炎。在13株产肠毒素大肠杆菌中，9株对多种抗生素耐药，它们将耐药性部分或全部转移到大肠杆菌K-12受体菌中。仅从马子宫炎中分离出的1株032血清型菌株，将氨苄西林、土霉素和强力霉素耐药性以及不耐热肠毒素生物合成决定簇整体转移。对接合子的质粒DNA分析显示存在一个41.8 MDa的接合性质粒。在子宫炎和败血症等特殊生态位中存在这种可自身转移的肠毒素生物合成复制子，表明肠毒素基因具有普遍存在的特性，可能是由于耐药基因的存在而被选择并传播。文中还讨论了通过此类质粒在动物与人类之间交叉感染的可能性。
