Serotypes, virulence factors and sensitivity against antibiotics of S-suis-strains isolated from clinically healthy as well as diseased pigs of Austrian swine herds

As Streptococcus suis biochemically identified 110 (104 from diseased and 6 from healthy pigs) strains were isolated from 33 diseased and from 5 healt hy herds, respectively. These strains were serotyped using commercially ava ilable antisera and determined for the production of extracellular protein (EF) and muramidase released protein (MRP). Further investigations comprise d adherence to HeLa-cells, binding to fibronectin as well as survival of th ese pathogens under different conditions, in particular temperature and pH- values. RAPD-fingerprinting of S. suis serotype 2 was compared with other s erotypes. Serotype 2 was most frequently found, followed by the serotypes 2 5, 16, 1, 21, 4, 11, 3, 5, 7, 17, 19, 24, and 28. 13 of the 110 strains exa mined could not be serotyped. EF, MRP, adherence to HeLa-cell-cultures and binding to fibronectin were observed in case of S. suis serotypes 1 and 2, but rarely in other types. The serotypes 1 and 2 were isolated from pigs su ffering from septicaemia and in a lower incidence from animals with meningi tis. The S. suis strains examined were killed by exposure to acid milieu (p H 4) and for 10 minutes at 60 degrees C. Using RAPD-fingerprinting-method S . suis serotype 2 was homogeneous and different from other serotypes. All S. suis strains as well as other streptococci biotypes isolated from pi gs examined were sensitive to penicillin, ampicillin and amoxicillin. 10 - 15 % of these pathogens were only intermediate sensitive and resistant to t iamulin and enrofloxacin, respectively.