Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
PLoS One. 2012;7(11):e49753. doi: 10.1371/journal.pone.0049753. Epub 2012 Nov 26.
Twenty-six isolates of Clostridium perfringens of different MLST types from chickens with necrotic enteritis (NE) (15 netB-positive) or from healthy chickens (6 netB-positive, 5 netB-negative) were found to contain 1-4 large plasmids, with most netB-positive isolates containing 3 large and variably sized plasmids which were more numerous and larger than plasmids in netB-negative isolates. NetB and cpb2 were found on different plasmids consistent with previous studies. The pathogenicity locus NELoc1, which includes netB, was largely conserved in these plasmids whereas NeLoc3, present in the cpb2 containing plasmids, was less well conserved. A netB-positive and a cpb2-positive plasmid were likely to be conjugative, and the plasmids were completely sequenced. Both plasmids possessed the intact tcp conjugative region characteristic of C. perfringens conjugative plasmids. Comparative genomic analysis of nine CpCPs, including the two plasmids described here, showed extensive gene rearrangements including pathogenicity locus and accessory gene insertions around rather than within the backbone region. The pattern that emerges from this analysis is that the major toxin-containing regions of the variety of virulence-associated CpCPs are organized as complex pathogenicity loci. How these different but related CpCPs can co-exist in the same host has been an unanswered question. Analysis of the replication-partition region of these plasmids suggests that this region controls plasmid incompatibility, and that CpCPs can be grouped into at least four incompatibility groups.
从患有坏死性肠炎（NE）的鸡（15 株 netB 阳性）或健康鸡（6 株 netB 阳性，5 株 netB 阴性）中分离到 26 株不同 MLST 型别的产气荚膜梭菌，这些菌株均含有 1-4 个大质粒，大多数 netB 阳性分离株含有 3 个大小不同的大质粒，这些质粒比 netB 阴性分离株中的质粒数量更多且更大。netB 和 cpb2 存在于不同的质粒上，这与之前的研究一致。致病性基因座 NELoc1 包括 netB，在这些质粒中基本保守，而存在于含有 cpb2 质粒中的 NeLoc3 则不太保守。netB 阳性和 cpb2 阳性的质粒可能是可接合的，这两个质粒均被完全测序。这两个质粒都具有产气荚膜梭菌可接合质粒特征的完整 tcp 可接合区域。对包括这两个质粒在内的 9 个 CpCPs 的比较基因组分析表明，存在广泛的基因重排，包括致病性基因座和附加基因的插入，而不是在骨架区域内。从这个分析中得出的模式是，各种与毒力相关的 CpCPs 的主要毒素携带区域被组织成复杂的致病性基因座。这些不同但相关的 CpCPs 如何能够在同一宿主中共存一直是一个未解决的问题。对这些质粒的复制-分配区域的分析表明，该区域控制着质粒的不相容性，并且 CpCPs 可以至少分为四个不相容组。
