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首页> 外文期刊>Infection and immunity >Colonization of the Respiratory Tract by a Virulent Strain of Avian Escherichia coli Requires Carriage of a Conjugative Plasmid
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Colonization of the Respiratory Tract by a Virulent Strain of Avian Escherichia coli Requires Carriage of a Conjugative Plasmid

机译：禽流感大肠杆菌的强毒株对呼吸道的定殖需要运输结合质粒

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The E3 strain of E. coli was isolated in an outbreak of respiratory disease in broiler chickens, and experimental aerosol exposure of chickens to this strain induced disease similar to that seen in the field. In order to establish whether the virulent phenotype of this strain was associated with carriage of particular plasmids, four plasmid-cured derivatives, each lacking two or more of the plasmids carried by the wild-type strain, were assessed for virulence. Virulence was found to be associated with one large plasmid, pVM01. Plasmid pVM01 was marked by introduction of the transposon TnphoA, carrying kanamycin resistance, and was then cloned by transformation of E. coli strain DH5α. The cloned plasmid was then reintroduced by conjugation into an avirulent plasmid-cured derivative of strain E3 which lacked pVM01. The conjugant was shown to be as virulent as the wild-type strain E3, establishing that this plasmid is required for virulence following aerosol exposure. This virulence plasmid conferred expression of a hydroxamate siderophore, but not colicins, on both strain E3 and strain DH5α. Carriage of this plasmid was required for strain E3 to colonize the respiratory tracts of chickens but was not necessary for colonization of the gastrointestinal tract. However, the virulence plasmid did not confer virulence, or the capacity to colonize the respiratory tract, on strain DH5α. Thus, these studies have established that infection of chickens with E. coli strain E3 by the respiratory route is dependent on carriage of a conjugative virulence plasmid, which confers the capacity to colonize specifically the respiratory tract and which also carries genes for expression of a hydroxymate siderophore. These findings will facilitate identification of the specific genes required for virulence in these pathogens.
机译：大肠杆菌E3菌株是在肉鸡的呼吸道疾病暴发中分离出来的，实验鸡对这种菌株的气溶胶暴露引起的疾病与现场观察到的相似。为了确定该菌株的强毒表型是否与特定质粒的运输相关，评估了四个质粒固化的衍生物的毒性，每个衍生物均缺乏野生型菌株携带的两个或多个质粒。发现毒力与一种大质粒pVM01有关。通过引入具有卡那霉素抗性的转座子TnphoA来标记质粒pVM01，然后通过转化大肠杆菌菌株DH5α将其克隆。然后通过缀合将克隆的质粒重新引入到无pVM01的菌株E3的无毒质粒固化的衍生物中。该结合物显示出与野生型菌株E3一样的毒性，证明该质粒是暴露于气溶胶​​后致病力所必需的。该毒力质粒使异羟肟酸酯铁载体在大肠杆菌E3和DH5α上均表达，但未表达大肠菌素。 E3菌株在鸡的呼吸道定植时需要该质粒的运输，但在胃肠道的定殖中则不需要。但是，毒力质粒对菌株DH5α没有赋予毒力，也没有赋予其在呼吸道定殖的能力。因此，这些研究已经确定，通过呼吸道途径感染大肠杆菌E3大肠杆菌的鸡依赖于结合性毒力质粒的运输，该结合性毒力质粒赋予了其在呼吸道中特异性定殖的能力，并且还携带了表达羟基酸盐的基因。铁载体。这些发现将有助于鉴定这些病原体中毒力所需的特定基因。

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