[Occurrence and diagnostic relevance of virulence-associated factors in Streptococcus suis].

Streptococcus suis (Sc. suis) can cause very different clinical entities. In contrast to Sc. suis-associated pneumonia, the induction of meningitis, septicemia, and polyarthritis by certain Sc. suis strains requires the expression of virulence factors that contribute to the invasiveness of the pathogen. In the presented study, we examined the occurrence of known virulence-associated factors in Sc. suis isolates from samples sent to the Institute of Microbiology, School of Veterinary Medicine Hannover, in order to evaluate their significance as potential virulence factors in different disease complexes in Northern Germany. The results show that (i) MRP + EF + serotype 2 and MRP* EF-serotype 9 strains are statistically significant associated with the disease complex meningitis/septicemia/arthritis and, thus, have to be considered invasive strains, (ii) serotyping alone is not sufficient for identification of virulent strains, (iii) there is a remarkable heterogeneity among pneumonia-associated Sc. suis strains and (iv) activity of haemolysin or suilysin appears to be not appropriate as virulence marker. Finally, it has to be noted that at present only half of the Sc. suis isolates from pigs with meningitis/septicemia/poyarthritis can be characterised by the detection of virulence-associated factors. Thus, the identification and characterisation of additional, serotype independent virulence factors of Sc. suis is a very important issue in future studies.