Vecht U, Wisselink H J, van Dijk J E, Smith H E
Department of Bacteriology, DLO-Central Veterinary Institute, Lelystad, The Netherlands.
Infect Immun. 1992 Feb;60(2):550-6. doi: 10.1128/iai.60.2.550-556.1992.
To determine whether the virulence of Streptococcus suis type 2 is associated with the phenotype of the strain, we infected newborn germfree pigs with 10 strains of S. suis type 2 categorized by three phenotypes. In an earlier study, the phenotypes were distinguished by the presence or absence of the muramidase-released protein (MRP) and an extracellular factor (EF) and were designated MRP+ EF+, MRP+ EF- and MRP- EF-. Pigs were first inoculated with Bordetella bronchiseptica to predispose them to infection and were then intranasally inoculated with the streptococci. Strains of the MRP+ EF+ phenotype induced fever and increased the number of polymorphonuclear leukocytes in blood. Specific clinical signs of disease such as nervous disorders and lameness were also observed. At necropsy bacteriologic and pathologic examination disclosed meningoencephalitis, polyserositis, and polyarthritis. Strains of the MRP+ EF- phenotype induced only nonspecific clinical signs of disease such as recumbency, lack of appetite, and fever; only slight pathologic changes were detected in the serosae. The four strains of the MRP- EF- phenotype induced no signs of disease. These findings indicate that the 110-kDa EF and, to a lesser degree, the 136-kDa MRP may be associated with the virulence of the bacterium. The results demonstrated that S. suis type 2 strains producing both MRP and EF are pathogenic for pigs.
为了确定2型猪链球菌的毒力是否与菌株表型相关，我们用10株按三种表型分类的2型猪链球菌感染新生无菌仔猪。在早期研究中，根据是否存在溶菌酶释放蛋白（MRP）和一种细胞外因子（EF）来区分表型，分别命名为MRP+ EF+、MRP+ EF-和MRP- EF-。仔猪首先接种支气管败血波氏杆菌使其易受感染，然后经鼻接种链球菌。MRP+ EF+表型的菌株引起发热，并增加血液中多形核白细胞的数量。还观察到了诸如神经紊乱和跛行等特定的疾病临床症状。尸检时，细菌学和病理学检查发现有脑膜脑炎、多浆膜炎和多关节炎。MRP+ EF-表型的菌株仅引起诸如躺卧、食欲不振和发热等非特异性疾病临床症状；在浆膜中仅检测到轻微的病理变化。MRP- EF-表型的四株菌株未引起疾病症状。这些发现表明，110 kDa的EF以及程度较轻的136 kDa的MRP可能与该细菌的毒力有关。结果表明，同时产生MRP和EF的2型猪链球菌菌株对猪具有致病性。
