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Virulence Plasmid Diversity in Clostridium perfringens Type D Isolates

机译：D型产气荚膜梭菌中毒力质粒多样性

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Clostridium perfringens type D isolates are important in biodefense and also cause natural enterotoxemias in sheep, goats, and occasionally cattle. In these isolates, the gene (etx) encoding ε-toxin is thought to reside on poorly characterized large plasmids. Type D isolates sometimes also produce other potentially plasmid-encoded toxins, including C. perfringens enterotoxin and beta2 toxin, encoded by the cpe and cbp2 genes, respectively. In the current study we demonstrated that the etx, cpe, and cpb2 genes are carried on plasmids in type D isolates and characterized the toxin-encoding plasmids to obtain insight into their genetic organization, potential transferability, and diversity. Southern blotting of pulsed-field gels showed that the etx gene of type D isolates can be present on at least five different plasmids, whose sizes range from 48 to 110 kb. The etx plasmids also typically carried IS1151 and tcp open reading frames (ORFs) known to mediate conjugative transfer of C. perfringens plasmid pCW3. PCR studies revealed that other than their tcp ORFs, etx plasmids of type D isolates do not carry substantial portions of the conserved or variable regions in the cpe plasmids of type A isolates. Southern blotting also demonstrated that in type D isolates the cpe and cpb2 genes are sometimes present on the etx plasmid. Collectively, these findings confirmed that the virulence of type D isolates is heavily plasmid dependent and indicated that (i) a single type D isolate can carry multiple virulence plasmids, (ii) a single type D virulence plasmid can carry up to three different toxin genes, and (iii) many etx plasmids should be capable of conjugative transfer.
机译：D型产气荚膜梭状芽孢杆菌在生物防御中很重要，并且还会在绵羊，山羊和偶尔的牛中引起天然肠毒素血症。在这些分离物中，编码ε-毒素的基因（ etx ）被认为存在于特征不充分的大质粒上。 D型分离物有时还会产生其他可能的质粒编码毒素，包括C。 perfringens 肠毒素和beta2毒素，分别由 cpe 和 cbp2 基因编码。在当前的研究中，我们证明了 etx ， cpe 和 cpb2 基因携带在D型分离物中的质粒上，并表征了毒素编码质粒以了解其遗传组织，潜在的可转移性和多样性。脉冲场凝胶的Southern印迹显示，D型分离株的 etx 基因可以存在于至少五个不同的质粒上，质粒的大小在48到110 kb之间。 etx 质粒通常还带有IS 1151 和 tcp 开放阅读框（ORF），已知它们可以介导 C的共轭转移。 perfringens 质粒pCW3。 PCR研究表明，除了它们的 tcp ORF外，D型分离株的 etx 质粒在cem A型分离株的质粒。 Southern印迹法还表明，在D型分离物中， etx 质粒有时存在 cpe 和 cpb2 基因。总的来说，这些发现证实D型分离株的毒力在很大程度上依赖于质粒，并表明（i）单个D型分离株可以携带多个毒力质粒，（ii）单个D型毒株可以携带多达三个不同的毒素基因。 ，以及（iii）许多 etx 质粒应能够进行共轭转移。

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