Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, Texas, USA.
J Bacteriol. 2013 Aug;195(16):3774-83. doi: 10.1128/JB.00500-13. Epub 2013 Jun 14.
Toxigenic Corynebacterium diphtheriae strains cause diphtheria in humans. The toxigenic C. diphtheriae isolate NCTC13129 produces three distinct heterotrimeric pili that contain SpaA, SpaD, and SpaH, making up the shaft structure. The SpaA pili are known to mediate bacterial adherence to pharyngeal epithelial cells. However, to date little is known about the expression of different pili in various clinical isolates and their importance in bacterial pathogenesis. Here, we characterized a large collection of C. diphtheriae clinical isolates for their pilin gene pool by PCR and for the expression of the respective pilins by immunoblotting with antibodies against Spa pilins. Consistent with the role of a virulence factor, the SpaA-type pili were found to be prevalent among the isolates, and most significantly, corynebacterial adherence to pharyngeal epithelial cells was strictly correlated with isolates that were positive for the SpaA pili. By comparison, the isolates were heterogeneous for the presence of SpaD- and SpaH-type pili. Importantly, using Caenorhabditis elegans as a model host for infection, we show here that strain NCTC13129 rapidly killed the nematodes, the phenotype similar to isolates that were positive for toxin and all pilus types. In contrast, isogenic mutants of NCTC13129 lacking SpaA-type pili or devoid of toxin and SpaA pili exhibited delayed killing of nematodes with similar kinetics. Consistently, nontoxigenic or toxigenic isolates that lack one, two, or all three pilus types were also attenuated in virulence. This work signifies the important role of pili in corynebacterial pathogenesis and provides a simple host model to identify additional virulence factors.
产毒白喉棒状杆菌菌株可导致人类白喉。产毒白喉棒状杆菌分离株 NCTC13129 产生三种不同的异三聚体菌毛，包含 SpaA、SpaD 和 SpaH，构成轴结构。已知 SpaA 菌毛介导细菌对咽上皮细胞的粘附。然而，迄今为止，对于不同临床分离株中不同菌毛的表达及其在细菌发病机制中的重要性知之甚少。在这里，我们通过 PCR 对大量白喉棒状杆菌临床分离株的菌毛基因库进行了特征分析，并通过针对 Spa 菌毛的抗体进行免疫印迹来检测相应菌毛的表达。与毒力因子的作用一致，SpaA 型菌毛在分离株中普遍存在，最重要的是，粘细菌对咽上皮细胞的粘附与 SpaA 菌毛阳性的分离株密切相关。相比之下，分离株中 SpaD 和 SpaH 型菌毛的存在存在异质性。重要的是，我们使用秀丽隐杆线虫作为感染模型宿主，证明了 NCTC13129 株迅速杀死线虫，其表型与毒素和所有菌毛类型均为阳性的分离株相似。相比之下，NCTC13129 的缺失 SpaA 型菌毛或缺失毒素和 SpaA 菌毛的同工型突变体对线虫的杀伤延迟，动力学相似。一致地，缺乏一种、两种或三种菌毛类型的非产毒或产毒分离株的毒力也减弱。这项工作表明菌毛在棒状杆菌发病机制中的重要作用，并提供了一种简单的宿主模型来鉴定其他毒力因子。
