Haemolytic activity of the Streptococcus milleri group' and relationship between haemolysis restricted to human red blood cells and pathogenicity in S. intermedius.

Abstract	A collection of 297 clinically documented 'Streptococcus milleri' strains, identified to the genotype level by 16S rRNA gene hydridisation, was screened for haemolysis of human and animal red blood cells. Forty-nine strains (65%) of the S. intermedius genotype displayed haemolysis restricted to human blood; they were named 'exclusive human haemolytic' (EHH) S. intermedius strains. The 26 remaining S. intermedius strains were named S. intermedius non-EHH strains. Quantitative studies on the haemolysis indicated that intermedilysin was the factor involved. The S. intermedius EHH strains represented the S. intermedius phenotype, whereas the S. intermedius non-EHH strains were phenotypically characteristic of S. constellatus. The complete 16S rRNA sequences of the S. intermedius EHH strains exhibited identity with S. intermedius strains ATCC 27335 (= NCDO 2227, NCTC 11324); the 16S rRNA sequences of the S. intermedius non-EHH strains were identical to S. constellatus strain ATCC 27823 (= NCDO 2226, NCTC 11325) except for positions 228 and 229 that carried an S. intermedius sequence signature. The 16S sequence similarities between the non-EHH strains and the S. constellatus and the S. intermedius type strains were 99.5% and 98.6%, respectively. Hybridisations of the complete 16S rRNA genes with oligonucleotide probes indicated a 16S rRNA homogeneity within the S. intermedius EHH and the non-EHH strains respectively. The S. intermedius EHH strains were isolated most frequently from infection- and abscess-related specimens. The present data emphasise the genetic variability within the S. constellatus species and redefine the S. intermedius species as a homogeneous group at the 16S rRNA level.
Authors	J A Jacobs, C S Schot, L M Schouls
Journal	Journal of medical microbiology (J Med Microbiol) Vol. 49 Issue 1 Pg. 55-62 (Jan 2000) ISSN: 0022-2615 [Print] England
PMID	10628826 (Publication Type: Journal Article)
Chemical References	RNA, Ribosomal, 16S
Topics	Animals Cattle Female Genetic Variation Genotype Hemolysis Horses Humans Male Phenotype Phylogeny RNA, Ribosomal, 16S (chemistry, genetics) Rabbits Sheep Species Specificity Streptococcus (classification, genetics, pathogenicity) Swine

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