Rioux S, Bégin C, Dubreuil J D, Jacques M
Groupe de Recherche sur les Maladies Infectieuses du Porc, and Département de pathologie et microbiologie, Faculté de médecine vétérinaire, Université de Montréal, C.P. 5000, St-Hyacinthe (Québec), Canada J2S 7C6.
Curr Microbiol. 1997 Sep;35(3):139-44. doi: 10.1007/s002849900227.
The major adhesin of Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, has been previously identified as lipopolysaccharide (LPS). The purpose of the present study was to isolate and characterize A. pleuropneumoniae LPS mutants. Screening of LPS mutants was performed with colony dot and sensitivity to novobiocin. One mutant obtained by colony dot (F19) and one mutant selected for its increased sensitivity to novobiocin (33.1) did not react with a monoclonal antibody against A. pleuropneumoniae serotype 1 O-antigen compared with the parent strain. Mutants F19 and 33.1 did not express high-molecular-mass LPS bands as determined in silver-stained SDS-PAGE gels. The core-lipid A region of mutant 33.1 and of the parent strain had similar relative mobilities and reacted with serum from a pig experimentally infected with the serotype 1 reference strain of A. pleuropneumoniae, while the same region in mutant F19 showed faster migration and did not react with this serum. Use of piglet tracheal frozen sections indicated that mutant F19 was able to adhere to piglet trachea as well as the parent strain, while mutant 33.1 adhered [half as much as] the parent strain. Finally, both LPS mutants were markedly less virulent in mice than the parent strain. Taken together, our observations support the idea that LPS is an important virulence factor of A. pleuropneumoniae.
猪胸膜肺炎放线杆菌是猪胸膜肺炎的病原体，其主要黏附素先前已被鉴定为脂多糖（LPS）。本研究的目的是分离并鉴定猪胸膜肺炎放线杆菌LPS突变体。通过菌落点样和对新生霉素的敏感性筛选LPS突变体。通过菌落点样获得的一个突变体（F19）和一个因对新生霉素敏感性增加而筛选出的突变体（33.1），与亲本菌株相比，它们不与抗猪胸膜肺炎放线杆菌1型O抗原的单克隆抗体发生反应。如在银染SDS-PAGE凝胶中所测定的，突变体F19和33.1不表达高分子量LPS条带。突变体33.1和亲本菌株的核心脂质A区域具有相似的相对迁移率，并与来自实验感染猪胸膜肺炎放线杆菌1型参考菌株的猪血清发生反应，而突变体F19的相同区域迁移更快，且不与该血清发生反应。使用仔猪气管冷冻切片表明，突变体F19与亲本菌株一样能够黏附于仔猪气管，而突变体33.1的黏附能力是亲本菌株的一半。最后，两种LPS突变体在小鼠中的毒力均明显低于亲本菌株。综上所述，我们的观察结果支持LPS是猪胸膜肺炎放线杆菌重要毒力因子这一观点。
