Characteristics of different Streptococcus suis ecovars and description of a simplified identification method.

Streptococcus suis strains associated with different animal hosts or located in different body regions constitute special ecovars of S. suis. A group of CO2-dependent strains which showed several unusual traits was found in the genital tract of swine, and mannitol- and sorbitol-fermenting strains were isolated from sheep, cattle and horses. S. suis was found to be biochemically more heterogenous than originally described. A detailed description is given of additional characteristics of the species as well as of characters which should be modified in the species description. A simple scheme which uses the amylase and the Voges-Proskauer (acetoin) reactions for the identification of S. suis is proposed. All S. suis strains tested produced a characteristic amylase reaction on Mueller-Hinton plates or on Columbia Agar Base enriched with starch.