Description of Six New Capsular Types (29–34) of Streptococcus Suis

Streptococcus suis is probably the most important veterinary pathogen among streptococcal species belonging to the Lancefield group D. During the last 2 decades, it has been associated with a variety of infections in pigs and was recognized as an important zoonotic agent. Since its official recognition as a species in 1987, S. suis has been found in many other animal species, including cattle, small ruminants, horses, dogs, and cats . The number of capsular types has increased from 9 in 1983 to 29 in 1991. Among all S. suis capsular types, capsular type 2 is always the most prevalent type isolated from diseased pigs in most countries where the swine industry is important. This type also is practically the only one that causes human cases of septicemia, meningitis, and endocarditis. The majority of other isolates associated with pathologic processes belongs to capsular types 1/2, 3, 4, 6, 7, 8, and 9. Some capsular types such as 18, 19, and 21 are generally recovered from clinically healthy animals. 10 The number of untypeable S. suis isolates is now relatively low. Because some of these isolates are recovered in large numbers from several tissues of a diseased animal, they are considered potential pathogens for animals and they become candidates for new capsular types. In this article, we describe and propose 6 new capsular types of S. suis, designated as 29, 30, 31, 32, 33, and 34. Bacterial strains included in this study were reference strains of S. suis capsular types 1-28 and 1/2 and 6 other strains representing proposed capsular types 29-34. Strains representing capsular types 29, 30, 32, and 34 were recovered from diseased pigs, whereas strains representing capsular types 31 and 33 were isolated from a diseased calf and a diseased lamb, respectively. One of the diseased pigs had meningitis and 1 had septicemia, and the last 2 were aborted fetuses. The 2-month-old Holstein calf was affected with a cerebral edema and a generalized vasculitis, and S. suis was isolated in large numbers from the brain and lungs. The lamb had marked posterior paresis, and the right coxal femoral joint had marked thickening of the joint capsule with fibrin present in the joint space. Bacteriologic culturing of the synovial fluid resulted in the recovery of a large pure population of S. suis. Capsular types 29, 30, 31, and 34 reference strains originated from the Clinical Bacteriology Laboratory of the Faculty of Veterinary Medicine at the University of Montreal, and capsular types 32 and 33 reference strains were provided by S. A. Rawiuk, Bacteriology Section, Animal Health Laborato-