Starcic Marjanca, Johnson James R, Stell Adam L, van der Goot Jeanet, Hendriks Henno G C J M, van Vorstenbosch Camillo, van Dijk Linda, Gaastra Wim
Department of Infectious Diseases and Immunology, Division of Bacteriology, Veterinary Faculty, University of Utrecht, P.O. Box 80.165, 3584 CL Utrecht, The Netherlands.
Vet Microbiol. 2002 Apr 2;85(4):361-77. doi: 10.1016/s0378-1135(02)00003-2.
Twenty-four haemolytic Escherichia coli strains were isolated from dogs with diarrhea. The strains were serotyped and analysed by polymerase chain reaction (PCR) for genes encoding virulence factors associated with E. coli that cause diarrhea in animals. Adhesion antigen production was deduced from haemagglutination experiments. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of heat extracts was also used as an indication for the production of adhesive structures. The majority of the strains was shown to produce this type of virulence factor. Adhesion and invasion tests of the strains and Caco-2 cells showed that all strains adhered and that two were invasive. The two invasive strains were positive in the intimin PCR and one of them also contained genes encoding CS31A. The PCR for heat stable toxin (ST) was positive in only four strains, as was the presence of F17 fimbrial genes. Surprisingly, 19 strains had intact P fimbrial operons, coding for an adhesin involved in urinary tract infection (UTI). The cytotoxic necrotising factor 1 (CNF1) gene, also mainly found in UTI was likewise detected in these 19 strains. Cytolethal distending toxin (Cdt) genes were found in five strains. The high number of strains positive for CNF1 and P fimbriae prompted us to test the strains in a multiplex PCR used to test E. coli isolated from UTI in various species for 30 virulence associated genes. The data showed that the majority of the diarrhea isolates have virulence factor profiles highly similar to UTI E. coli isolates from dogs. This raises the question whether these isolates are real intestinal pathogens or "innocent bystanders". However, since CNF1 producing necrotoxic E. coli (NTEC) strains isolated from humans, pigs and calves with diarrhea appear to be highly related to our strains, it might be that in dogs this type of isolate is capable of causing not only UTI, but also diarrhea. If this is the case and this type of isolate is "bifunctional", domestic animals likely constitute a reservoir of NTEC strains which can be also pathogenic for humans.
从患有腹泻的犬只中分离出24株溶血性大肠杆菌菌株。对这些菌株进行血清分型，并通过聚合酶链反应（PCR）分析编码与导致动物腹泻的大肠杆菌相关毒力因子的基因。通过血凝试验推断粘附抗原的产生。热提取物的十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）也被用作产生粘附结构的指标。大多数菌株显示产生这种类型的毒力因子。对这些菌株和Caco-2细胞进行的粘附和侵袭试验表明，所有菌株都能粘附，其中两株具有侵袭性。这两株侵袭性菌株在内毒素PCR中呈阳性，其中一株还含有编码CS31A的基因。仅4株菌株的热稳定毒素（ST）PCR呈阳性，F17菌毛基因的情况也是如此。令人惊讶的是，19株菌株具有完整的P菌毛操纵子，该操纵子编码参与尿路感染（UTI）的一种粘附素。同样主要在UTI中发现的细胞毒性坏死因子1（CNF1）基因也在这19株菌株中被检测到。在5株菌株中发现了细胞致死性膨胀毒素（Cdt）基因。大量菌株的CNF1和P菌毛呈阳性，促使我们使用一种多重PCR对这些菌株进行检测，该多重PCR用于检测从不同物种的UTI中分离出的大肠杆菌的30个与毒力相关的基因。数据显示，大多数腹泻分离株的毒力因子谱与犬只UTI大肠杆菌分离株高度相似。这就提出了一个问题，即这些分离株是真正的肠道病原体还是“无辜的旁观者”。然而，由于从患有腹泻的人类、猪和小牛中分离出的产生CNF1的坏死性毒力大肠杆菌（NTEC）菌株似乎与我们的菌株高度相关，可能在犬只中这种类型的分离株不仅能够引起UTI，还能导致腹泻。如果是这样，并且这种类型的分离株是“双功能的”，那么家畜可能构成了NTEC菌株的储存库，这些菌株对人类也可能具有致病性。
