PRESENCE OF VIRULENCE MARKERS IN POLISH STREPTOCOCCUS SUIS FIELD ISOLATES

The objective of this study was to detect proteins related with the virulence of Streptococcus suis (S. suis): muramidase-released protein (MRP), extracellular factor (EF), and suilysin (SLY), using the Western blot procedure. The strains were isolated in Poland from pigs with clinical symptoms and pathological lesions of streptococcosis. Eleven phenotypes were identified among the tested strains of serotype 2. Half of them (43) produced all three proteins, i.e. 40 strains (46.51%) produced standard molecular mass proteins (MRP+ EF+ SLY+) and three isolates (3.49%) produced MRP, EF*, and SLY. Thirteen strains (15.12%) produced two proteins. Twenty-three (26.75%) strains synthesised only one protein. No proteins were detected in seven (8.13%) strains. S. suis isolates belonging to serotypes other than serotype 2 represented six phenotypes. There was no isolate synthesising all the three potential virulence factors in this group. These results show that MRP, EF, and SLY are produced in 50% of the strains. Because these isolates originate from diseased pigs, also other factors than MRP, EF, and SLY must be involved in S. suis virulence.