Streptococcus tigurinus sp. nov., isolated from blood of patients with endocarditis, meningitis and spondylodiscitis

Abstract

Four Gram-stain-positive, catalase-negative, coccus-shaped bacterial strains were isolated from multiple blood cultures of patients with endocarditis, meningitis and spondylodiscitis. The isolates were tentatively identified as viridans streptococci on the basis of phenotypic characteristics. Comparative 16S rRNA gene sequencing studies showed that the organisms were members of theStreptococcus mitisgroup but did not correspond to any recognized species. The nearest phylogenetic relative wasS. mitisATCC 49456T, with 98.6 % sequence similarity. The representative strain AZ_3aTshowed less than 96.8, 97.6, 94.5 and 95.5 % similarity to the phylogenetically most closely related species byrecA,rpoB,sodAandgroELgene sequence analysis, respectively. DNA–DNA hybridization analyses showed a low reassociation value of 32.2 % between strain AZ_3aTandS. mitisDSM 12643T. Reassociation values with members of otherS. mitisgroup species ranged from 27.3 to 49.7 %. The G+C content of the DNA was 40.0 mol%. Based on our biochemical and molecular analyses, the isolates represent a novel species, for which the nameStreptococcustigurinussp. nov. is proposed. The type strain is AZ_3aT( = CCOS 600T = DSM 24864T).