Biochemical and molecular genetic studies were performed on an unknown Gram-positive, catalase-negative, coccus-shaped organism isolated from clinical samples from pigs. On the basis of the results of cellular morphological and biochemical tests, the organism was identified as a streptococcal species. 16S rRNA gene sequence comparisons confirmed its identification as a member of the genus Streptococcus, but the organism was distinct from any recognized species of this genus. The closest phylogenetic relative of the unknown organism corresponded to Streptococcus suis NCTC 10234(T) (97.2 % 16S rRNA gene sequence similarity) and this phylogenetic position was confirmed by analysis of rpoB and sodA sequences. DNA-DNA hybridization studies showed that the unidentified organism produced a DNA reassociation value of 36.6 % with respect to S. suis NCTC 10234(T). The novel bacterium was distinguished from S. suis and other Streptococcus species using biochemical tests. On the basis of phenotypic and phylogenetic data, the unidentified organism represents a novel species of the genus Streptococcus, for which the name Streptococcus plurextorum sp. nov. is proposed. The type strain is 1956-02(T) (=CECT 7308(T)=CCUG 52972(T)).