title: 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.forename: J A
authors.initials: JA
authors.lastname: Jacobs
authors.affiliation: Department of Medical Microbiology, University Hospital of Maastricht, PO Box 5800, 6202 AZ Maastricht and *Research Laboratory for Infectious Diseases, National Institute of Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands.
authors.forename: C S
authors.initials: CS
authors.lastname: Schot
authors.affiliation: Department of Medical Microbiology, University Hospital of Maastricht, PO Box 5800, 6202 AZ Maastricht and *Research Laboratory for Infectious Diseases, National Institute of Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands.
authors.forename: L M
authors.initials: LM
authors.lastname: Schouls
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006461:Hemolysis; D006736:Horses; D006801:Humans; D008297:Male; D010641:Phenotype; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D011817:Rabbits; D012756:Sheep; D013045:Species Specificity; D013291:Streptococcus / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D013552:Swine
chemical_list: D012336:RNA, Ribosomal, 16S