Kennedy Catherine L, Krejany Efrosinia O, Young Lauren F, O'Connor Jennifer R, Awad Milena M, Boyd Richard L, Emmins John J, Lyras Dena, Rood Julian I
Australian Bacterial Pathogenesis Program, Department of Microbiology, Monash University, Vic. 3800, Australia.
Mol Microbiol. 2005 Sep;57(5):1357-66. doi: 10.1111/j.1365-2958.2005.04774.x.
Clostridium septicum is the causative agent of spontaneous gas gangrene or atraumatic myonecrosis, a sudden and frequently fatal infection that is increasingly associated with malignancy of the colon. Little is known about the disease process although the focus of virulence studies has been the alpha-toxin, a pore-forming cytolysin that is encoded by the csa gene and secreted as an inactive protoxin. Until now a lack of techniques for the genetic manipulation of C. septicum has hindered the use of molecular approaches to understand pathogenesis. By introducing plasmids by conjugation from Escherichia coli, we have developed methods for the genetic manipulation of C. septicum and constructed a chromosomal csa mutant by allelic exchange. Virulence testing of an isogenic series of strains consisting of the wild type, the csa mutant, and a csa mutant complemented with the wild-type csa gene revealed that the development of fulminant myonecrosis in mice was dependent on the ability to produce a functional haemolytic alpha-toxin. Furthermore, the inhibition of leukocyte influx into the lesion, which is very typical of clostridial myonecrosis, was also dependent on the ability to produce alpha-toxin. This study represents the first definitive identification of a virulence factor in this organism and opens the way for further studies that will delineate the role of other putative virulence factors in this significant pathogen.
败血梭菌是自发性气性坏疽或非创伤性肌坏死的病原体，这是一种突然发作且常致命的感染，越来越多地与结肠癌相关。尽管毒力研究的重点是α毒素，一种由csa基因编码并作为无活性原毒素分泌的成孔细胞溶素，但对该疾病过程知之甚少。到目前为止，缺乏对败血梭菌进行基因操作的技术阻碍了利用分子方法来理解发病机制。通过从大肠杆菌进行接合转移引入质粒，我们开发了对败血梭菌进行基因操作的方法，并通过等位基因交换构建了一个染色体csa突变体。对由野生型、csa突变体和补充有野生型csa基因的csa突变体组成的同基因系列菌株进行毒力测试，结果表明小鼠暴发性肌坏死的发展取决于产生功能性溶血α毒素的能力。此外，抑制白细胞流入病变部位，这是梭菌性肌坏死的典型特征，也取决于产生α毒素的能力。这项研究首次明确鉴定了该生物体中的一种毒力因子，并为进一步研究开辟了道路，这些研究将阐明其他假定毒力因子在这种重要病原体中的作用。
