Description of 14 new capsular types of Streptococcus suis.

Fourteen new capsular types of Streptococcus suis (types 9 to 22) are described. All reference strains are morphologically and biochemically similar to types previously described. Reference strain types 9 to 13, 15, 16, and 22 were isolated from diseased pigs, whereas types 17 to 19 and 21 came from clinically healthy pigs; type 14 was isolated from a human case of meningitis, and type 20 was isolated from a diseased calf. The group T streptococcus of de Moor has been included in the typing system as type 15. Two-way cross-reactions between types 6 and 16 and a one-way cross-reaction between types 2 and 22 have been demonstrated. In addition, several cross-reactions probably not due to capsular material were detected among different types by using the coagglutination test. This test should not be used alone; weak or multiple positive reactions must be confirmed by the capsular reaction test or the capillary precipitation test.