Multi-locus sequence typing (MLST) of Serotype B III Streptococcus and correlation with pathogenic potential
Ms Nicola Jones, Professor Carol Baker, Professor Elsayed Sameer, Professor H.Dele Davies
- Start Date:
01 January 2002
Alberta Children's Hospital, Calgary, Canada
GBS serotype III is responsible for ~ 80% of meningitis cases due to GBS. In a recent study of 1207 pregnant women in Alberta, we compared the serotype distributions of vaginal-rectal GBS isolates to all isolates from neonates with invasive GBS disease. We also determined serum concentrations of Ia, Ib, II, III, and V CPS-specific IgG according to serotype of the vaginal-rectal colonizing GBS strain. Serotype III accounted for 20.6% (48/233) of colonizing strains, but 37% (27/73) of invasive isolates from neonates were of this serotype(P<0.01). Maternal colonization with type III was least likely to be associated with moderate concentrations of serotype III CPS-specific IgG suggesting that serotype III GBS is more invasive than other serotypes in our population. However, it is apparent that colonization with some serotype III isolates is associated with low maternal antibodies while others are associated with high maternal antibodies. The reasons for these differences have not yet been explored. We hypothesize that using multi-locus serotyping (MLST), we will identify two major groups (divisions) in serotype III. One group will more likely be associated with low maternal antibodies (high virulence group) and neonatal disease, while the other group will more likely be associated with higher maternal antibodies (low virulence group) and less commonly associated with neonatal disease. Our study may lead to a better understanding of the pathogenic factors associated with type III GBS meningitis. This may in turn lead to therapeutic maneuvers, including development of appropriate vaccines or other methods of prevention.
Results from this study have been published in a scientific journal as follows:
Davies HD, Jones N, Whittam TS, Elsayed S, Bisharat N, Baker CJ,
Multilocus sequence typing of serotype III group B streptococcus and correlation with pathogenic potential.
J Infect Dis 2004 Mar 15;189(6):1097-102. Epub 2004 Feb 27. http://www.journals.uchicago.edu/JID/journal/issues/v189n6/31175/31175.web.pdf