Production of Muraminidase-Released Protein (MRP), Extracellular Factor (EF) and Suilysin by field isolates of Streptococcus suis capsular types 2, 1/2, 9, 7 and 3 isolated from swine in France

A total of 323 isolates of Streptococcus suis recovered from diseased or he althy pigs in France were serotyped. The presence of virulence-related prot eins, Muraminidase-Released Protein (MRP), Extracellular Factor (EF) and Su ilysin was also studied in 122 isolates of capsular types 2, 1/2, 9, 7 and 3 to evaluate their implication in virulence of S. suis. Capsular types 2, 1/2, 9, 7 and 3 were the most frequently detected (93%), with 69% for the c apsular type 2 alone. Capsular types 2, 1/2, 9, 7, 3, 1, 4, 8, 18, 10 and 1 2 were isolated from diseased pigs, whereas types 2, 7, 9, 1/2, and 3 origi nated from the nasal cavities or tonsils of healthy animals. Most of the S. suis type 2 isolates recovered from diseased pigs carried MRP+EF-Suilysin- (46%) or MRP+EF+Suilysin+(28%) phenotypes. The MRPI-EF-Suilysin-phenotype w as also detected in 67% of S. suis type 2 strains isolated from healthy pig s. The production of the virulence-related proteins was less frequently fou nd in S. suis types 1/2, 9, 7 and 3 recovered either from diseased or healt hy pigs. In this study, all the capsular type 1/2 strains were MRP+EF-Suily sin- and all the S. suis type 7 harboured an MRP-EF-Suilysin-phenotype. The MRP-EF-Suilysin-phenotype was found in S. suis types 2, 3, 7 and 9 isolate d from septicaemia, meningitis, pneumonia, and pleurisy. These results sugg est that the presence of these proteins should not be used as a single cond ition for classifying the virulence of a field isolate in France.