Numerical taxonomic, chemical and clinical studies on group b streptococci.
thesisposted on 19.11.2015, 09:10 by Ayad Fadhil Yousif. Nakkash
One hundred and eighty-three strains of the genus Streptococcus (19 strains were representatives of serological Groups A, C, D, E, F. G, H, K, M, N, O and Q; and 164 strains of serological Group B from bovine and human sources) were tested for 103 characters based on their morphology, physiology and biochemistry. Computer analysis of the results indicated that the majority of strains received as serological Group B grouped into eight clusters distinct from streptococci of other serological Groups. Serological grouping and typing, phage typing, plasmid studies, moles % G+C and DNA-DNA hybridization, and chemical analysis of the polar lipids were performed on representative strains from each of the eight numerical taxonomic clusters. The results indicate that while there are differences between strains of streptococci of serological Group B (Streptococcus agalactiae) on the basis of biochemical tests, serotyping and phage typing, there is no correlation between any of these differences and source of isolation. The differences between the strains, whether they be isolated from human or bovine sources, are no greater than might be expected due to variation within one bacterial species. This conclusion is supported by the results of the polar lipid and DNA studies. Indeed, all the evidence presented here strongly suggests that streptococci of serological Group B which cause human and bovine diseases are in fact all members of one species, Streptococcus agalactiae. Of interest is the isolation of plasmids from, one strain of bovine origin but none from the human strains examined. However, on the basis of this preliminary plasmid study, there is no evidence that the presence of such plasmids has any role in the pathogenicity of these bacteria. Further work is necessary to elucidate the biochemical or genetical basis of pathogenicity in the species Streptococcus agalactiae. The carriage rate of streptococci of serological Group B in pregnant women and their neonates living in the Leicester area was assessed during a six months clinical survey (May to October 1979) conducted at the Leicester Royal Infirmary. The isolates were serogrouped and sero- and phage-typed in order to determine the spread of the bacteria.