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Research Article

Streptococcus peroris sp. nov. and Streptococcus infantis sp. nov., new members of the Streptococcus mitis group, isolated from human clinical specimens

Kawamura, Yoshiaki, Hou, Xiao-Gang, Todome, Yuko, Sultana, Ferdousi, Hirose, Kenji, Shu, Sin-Ei, Ezaki, Takayuki, Ohkuni, Hisashi

International Journal of Systematic and Evolutionary Microbiology 1998; 48(3):921 · https://doi.org/10.1099/00207713-48-3-921

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Summary auto-generated

This study describes the discovery and characterization of two new streptococcal species isolated from human clinical specimens, particularly from children with Kawasaki disease and other conditions. Eight alpha-haemolytic streptococcal strains showed very low DNA-DNA hybridization similarity (less than 33%) with all established members of the Streptococcus mitis group, indicating they represented novel taxa. These eight strains were divided into two distinct similarity groups based on DNA-DNA hybridization data, biochemical testing, and 16S rRNA gene sequencing. Group I strains formed a phylogenetic branch near S. gordonii, while Group II strains clustered with the S. mitis-S. oralis-S. pneumoniae complex. Both groups showed approximately 97-98% 16S rRNA sequence identity with S. mitis, but only 40-60% DNA-DNA homology with each other. Biochemical analysis distinguished each group, particularly in carbohydrate fermentation patterns, enzyme production, and enzymatic substrate utilization. The authors propose two new species names: Streptococcus peroris (Group I, type strain O-66T) and Streptococcus infantis (Group II, type strain O-122T). Both species are facultatively anaerobic, alpha-haemolytic, Gram-positive cocci isolated from human tooth surfaces and pharyngeal specimens.

Key findings

  • Two novel streptococcal species were identified from human clinical isolates showing less than 33% DNA-DNA homology with known Streptococcus mitis group members but phylogenetically belonging to this group
  • Streptococcus peroris (Group I) and Streptococcus infantis (Group II) can be differentiated by biochemical characteristics including differential carbohydrate utilization and enzyme production patterns
  • Although these two new species share 97.2% 16S rRNA gene sequence similarity with each other, they form distinct phylogenetic branches within the mitis group based on DNA-DNA hybridization data, demonstrating the importance of multiple molecular methods for accurate bacterial taxonomy
  • Both species were isolated from human tooth surfaces and pharynx, with S. infantis associated with Kawasaki disease in pediatric patients

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Abstract

Taxonomic studies were performed on eight strains of α-haemolytic streptococci that showed very low DNA-DNA hybridization similarity values with all established members of the mitis group of the genus Streptococcus. These strains were isolated from the tooth surface and pharynx of humans. 16S rRNA gene sequence analysis showed that these strains belonged to the mitis group, but that they fell into two new branches. DNA-DNA hybridization demonstrated two new similarity groups. From the results of the present study, the names Streptococcus peroris sp. nov. and Streptococcus infantis sp. nov. are proposed for these new groups. The type strains are 0–66T(= GTC 848T= JCM 10158T) and 0–122T(= GTC 849T= JCM 10157T), respectively.