Distribution of capsular types and production of muramidase-released protein (MRP) and extracellular factor (EF) of Streptococcus suis strains isolated from diseased pigs in seven European countries

Streptococcus suis strains (n=411), isolated from diseased pigs in seven Eu ropean countries were serotyped using specific antisera against serotype 1 to 28, and were phenotyped on the basis of their muramidase-released-protei n (MRP) and extracellular-factor protein (EF) production. Overall, S. suis serotype 2 appeared to be most prevalent (32%), followed by serotype 9 (20% ) and serotype 1 (12%). Serotype 2 was most frequently isolated in France, Italy and Spain, whereas serotype 9 was most frequently isolated in Belgium , The Netherlands and Germany. In the United Kingdom serotypes 1 and 14 wer e most frequently isolated. High percentages of S. suis serotype 1, 2, 1/2 and 14 strains, isolated from tissues associated with S, suis infections su ch as brain, serosa, joint, heart and organs expressed the EF-protein, indi cating that in these serotypes expression of EF is likely to be associated with virulence. In contrast, strains belonging to serotype 7 and 9, isolate d from tissues associated with S. suis infections did not produce EF. These results strongly suggest that in the serotypes 7 and 9 EF expression is no t related to virulence. More than 80% of the S. suis serotype 9 strains pro duced an MRP* protein, a high molecular variant of the 136 kDa MRP. Express ion of MRP* in serotype 9 strains is possibly associated with virulence. (C ) 2000 Elsevier Science B.V. All rights reserved.