Dezfulian Hojabr, Batisson Isabelle, Fairbrother John M, Lau Peter C K, Nassar Atef, Szatmari George, Harel Josée
Groupe de Recherche sur les Maladies Infectieuses du Porc, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Canada.
J Clin Microbiol. 2003 Apr;41(4):1375-85. doi: 10.1128/JCM.41.4.1375-1385.2003.
The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165(1) and F165(2). F165(1) is encoded by the foo operon (pap-like), and F165(2) is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.
对最初从患病犊牛或仔猪中分离出的18株F165阳性大肠杆菌菌株的毒力基因型谱和致病岛（PAI）的存在情况进行了研究。根据其黏附表型和基因型，将这些肠道外致病菌株分为三组。F165菌毛复合体至少由两种血清学和遗传学上不同的菌毛组成：F165(1)和F165(2)。F165(1)由foo操纵子（类pap）编码，F165(2)由fot（与sfa相关）编码。第1组菌株foo和fot呈阳性，第2组菌株foo和afa呈阳性，第3组菌株仅foo呈阳性。对这些菌株检测了主要在肠道外致病性大肠杆菌（ExPEC）菌株中发现的毒力基因的存在情况。虽然所有菌株编码F11菌毛的papA变体、incD、traT和papC均呈阳性，但与ExPEC菌株相关的PAI中常见的毒力基因的流行率差异很大，第2组菌株携带了大多数检测的毒力基因。在第1组的所有菌株和第3组的一株菌株中检测到了papG等位基因III。所有其他菌株对编码PapG黏附素的已知等位基因均呈阴性。通过脉冲场凝胶电泳和DNA杂交对这些菌株中毒力基因与tRNA基因的关联进行了表征。在18株菌株中的16株中，foo操纵子的插入位点位于pheU tRNA基因座，另外2株位于selC tRNA基因座。此外，18株菌株中有8株含有一个高致病性岛，该岛插入到asnT或asnV/U tRNA基因座中。这些结果表明动物败血症菌株中存在一个或多个PAI，并且foo操纵子与这些岛中的至少一个相关。F165阳性菌株与ExPEC具有某些毒力特征，并且如在实验感染中所测试的，它们中的大多数对仔猪具有致病性。
