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

А Stanojkovic,Z Skrbic,V Mandic,A Stanojkovic-Sebic,M Gogic,N Stanisic,М.M Petrovic

doi:10.2298/bah1404699s

Abstract

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, ?-glucoronidase, ?-galactosidase, ?-galactosidase, methyl-?-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 ?-glucoronidase (?GUR) and ?- galactosidase (?GAL), were significant in differentiation of this bacteria from other similar streptococci, along with some other crucial features (? hemolysis on blood sheep agar, absence of growth in 6,5% NaCl broth).

Highlights

Streptococcus suis is a facultative anaerobic, coccoid, gram-positive bacterium with the ability to synthesize capsule and secrete hemolysin
Since it is a very good colonizer of the mucosal surfaces, clinically healthy pigs are the main reservoir of infection, and the most important link in the epidemiology of human infections caused by S. suis (Gottschalk et al, 2010)
The material analysed in this study included 186 tonsil and nose swabs of clinically healthy pigs and 40 meningeal, renal and joint samples of deceased pigs that had symptoms resembling those associated with S. suis infection

Summary

Introduction

Streptococcus suis is a facultative anaerobic, coccoid, gram-positive bacterium with the ability to synthesize capsule and secrete hemolysin It has components of the cell wall antigens similar to those displayed by group D streptococci. S. suis is a normal inhabitant of the pigs respiratory system, mostly of the tonsils and nasal cavities, and can often be isolated from the genital and gastrointestinal systems in healthy animals (Higgins and Gottschalk, 2005). Since it is a very good colonizer of the mucosal surfaces, clinically healthy pigs are the main reservoir of infection, and the most important link in the epidemiology of human infections caused by S. suis (Gottschalk et al, 2010). S. suis can be isolated from noses and tonsils of live pigs, as well as from pig carcasses and butchers' knives (Stanojkovic et al, 2012)

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