Distribution of the intermedilysin gene among the anginosus group streptococci and correlation between intermedilysin production and deep-seated infection with Streptococcus intermedius

The distribution of intermedilysin, a human-specific cytolysin, among the a nginosus group streptococci and the correlation of toxin production and inf ection by Streptococcus intermedius were investigated, PCR and Southern hyb ridization specific for the intermedilysin gene revealed that the toxin gen e exists only in S. intermedius and no homologue to the toxin gene is distr ibuted in S. anginosus and S. constellatus, Thus, the intermedilysin gene i s useful as a marker gene of S. intermedius. Moreover, a human-specific hem olysis assay and Western blotting with intermedilysin-specific antibodies c learly demonstrated that the intermedilysin production level in isolates fr om deep-seated infections, such as brain and liver abscesses, is higher (6. 2- to 10.2-fold, respectively) than in strains from normal habitats, such a s dental plaque, or from peripheral infection sites. However, other candida te virulence factors of S, intermedius, such as chondroitin sulfate depolym erase, hyaluronidase, and sialidase activities, did not show such a clear c orrelation between enzymatic activity and isolation sites or disease severi ty, From these results, intermedilysin is likely to be the pathogenic or tr iggering factor of significance in inducing deep-seated infections with S. intermedius.