Department of Animal Health and Bioscience, Faculty of Agricultural Sciences, Aarhus University, Blichers Alle 20, PO Box 50, DK-8830 Tjele, Denmark.
Vet Microbiol. 2010 Jul 29;144(1-2):231-5. doi: 10.1016/j.vetmic.2009.12.036. Epub 2010 Jan 11.
The Clostridium perfringens necrotic enteritis toxin B, NetB, was recently proposed as a new key virulence factor for the development of necrotic enteritis (NE) in broilers. The aim of the present study was to investigate the presence of the netB gene and the in vitro production of the NetB toxin in a well characterized collection of 48 C. perfringens Type A isolates, obtained from Danish broiler flocks. The investigation revealed netB gene prevalences of approx. 50% and 60% among isolates from diseased (NE) and healthy flocks, respectively. Only minor nucleotide variations were observed between the isolates in the coding sequence (CDS) of the netB gene, and the promoter region was observed to be completely conserved. However, in vitro NetB production was only observed in 4 out of 14 netB-positive C. perfringens isolates recovered from healthy birds, whereas 12 out of 13 netB-positive isolates from NE birds were shown to produce the NetB toxin. It is therefore proposed that genotype, i.e. presence of the netB gene, in itself is inadequate for predicting virulence of C. perfringens, and future investigations should focus on the bacterial phenotypes; the regulatory mechanisms involved in the expression of NetB, and potentially also other toxins, and its implications for the virulence of individual C. perfringens strains.
产气荚膜梭菌坏死性肠炎毒素 B（NetB）最近被提议为坏死性肠炎（NE）在肉鸡中发展的一个新的关键毒力因子。本研究的目的是调查在从丹麦肉鸡群中获得的经过良好特征描述的 48 株 A 型产气荚膜梭菌的集合中，netB 基因的存在以及 NetB 毒素的体外产生情况。研究结果表明，来自发病（NE）和健康鸡群的分离株的 netB 基因的流行率分别约为 50%和 60%。在 netB 基因的编码序列（CDS）中，观察到分离株之间的核苷酸变异很小，并且启动子区域被观察到完全保守。然而，仅在从健康鸟类中回收的 14 株 netB 阳性产气荚膜梭菌分离株中的 4 株中观察到体外 NetB 产生，而在来自 NE 鸟类的 13 株 netB 阳性分离株中，有 12 株被证实产生了 NetB 毒素。因此，建议基因型（即 netB 基因的存在）本身不足以预测产气荚膜梭菌的毒力，未来的研究应集中于细菌表型；涉及 NetB 表达的调节机制，以及可能涉及其他毒素的调节机制，及其对个别产气荚膜梭菌菌株毒力的影响。
