Study of cell surface associated virulence factors of Streptococcus parauberis strains pathogenic for turbot

The cell surface characteristics of a collection of Streptococcus pamuberis strains isolated from turbot were examined, including the autoagglutinatin g and hemagglutinating capacities and the hydrophobic character. In additio n, their possible relationship with the adhesive and invasive abilities of the strains was determined. S. parauberis isolates showed only hemagglutina ting activity against turbot erythrocytes indicating host specificity for t his character. Although hydrophobicity results were variable depending on t he method employed, a good correlation was observed between BATH (adherence to hydrocarbons) and NCF (binding to nitrocellulose filters) tests. In add ition, the growth media influenced the hydrophobic character of the strains , probably due to the induction of synthesis of capsular material. On the o ther hand, all the isolates from turbot of S. parauberis were moderately ad herent and invasive in different poikilotherm and homoiotherm cell lines. I nhibition experiments showed that lipoteichoic acids markedly reduced the a dherence levels, suggesting that these molecules are implicated in the adhe sive mechanism of this fish pathogen.