Biochemical characteristics of Streptococcus suis strains isolated from healthy and deceased pigs

The aim of this study was to determine the biochemical properties of Streptococcus suis strains isolated from healthy and deceased pigs. For this research we tested 34 S. suis strains isolated from deceased pigs that had clinical signs of septicemia and meningitis, as well as from clinically healthy pigs. The strains that have been already confirmed with specific antisera were tested using commercial battery of biochemical tests (API 20 Strep and ID 32 Strep) to determine the dominant biochemical characteristics that can be used in diagnosis of bacterial infection if specific S. suis antisera are not available. The main results showed that all S. suis strains were postive in esculine, trehalose, glycogen, lactose, sacharose, starch, leucine aminopeptidase, alanine-phenyl-alanine-proline arylamidase tests, while negative in Voges-Proskauer, hipurate, ribose, arabinose and sorbitol tests. S. suis strains were in high percentage positive in arginine dihydrolase, β-glucoronidase, α-galactosidase, β-galactosidase, methyl-β-dglucopyranoside, glycyl-tryptophan arylamidase and inulin tests. Athough S. suis is in highly positive in some tests, it can be concluded that Voges-Proskauer, hipurate, trehalose, esculine tests, along with β-glucoronidase (βGUR) and α- galactosidase (αGAL), were significant in differentiation of this bacteria from other similar streptococci, along with some other crucial features (α hemolysis on blood sheep agar, absence of growth in 6,5% NaCl broth). [Projekat Ministarstva nauke Republike Srbije, br. TR 31053]