The strain and clonal identity of blood and oral isolates of viridans streptococci (S. salivarius, S. mitis, S. mutans and S. sanguis groups) has been tested in a group of 30 patients with positive haemocultures. Isolates were preliminarily identified by means of biochemical properties and then genotyped by means of the PCR (spacer 16S and 23S rDNA) and AP-PCR. Strain identity of blood and oral isolates has been proved in S. salivarius in 2 of 4 cases, in S. mitis in 8 of 10 cases, in S. mutans in 2 of 2 cases and in S. sanguis in 15 of 16 cases. Clonal identity of blood and oral isolates has been proved in 50 % of isolates. Oral microbial flora is thus the significant source of viridans streptococci in positive haemocultures.

        Key words: viridans streptococci – oral and blood isolates – molecular genetic identification