This study was aimed to examine the genetic characteristics of 44 Streptococcus suis type 2 (SS2) isolates and the virulence attributes of 23 representative isolates. Multilocus sequence typing revealed five sequence types (ST1, ST7, ST28, ST86, and ST162) with 19 isolates assigned to ST7 (43.2%), 14 to ST1 (31.8%), and 9 to ST28 (20.5%). PCR typing of the pilus gene clusters classified the isolates into three types: A (72.7%), B (22.7%), and N (4.5%). All isolates of pilus types A and N were assigned to the ST1 complex containing ST1, ST7, and ST86, while those of type B belonged to the ST27 complex comprising ST28 and ST162. Only two strains had the putative pathogenicity island 89-kb cluster (89K) and were of type N. The type B strains had a significantly lower adhesion, were more readily killed by macrophage, and had lower virulence to mice than those of types A and N. We conclude that SS2 strains of both ST1 and ST27 complexes, parallel to pilus types A and B, were prevalent in the pig populations in Zhejiang Province, and ST7 and ST1 strains were the predominant genotypes in the diseased pigs with pneumonia.

Institute of Preventive Veterinary Medicine and Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine Zhejiang University Hangzhou 310029 China