NEW YORK (Reuters Health) - Using genome-wide investigative methods, researchers have clarified the molecular events in M3 group A Streptococcus (GAS) strains that lead to the emergence of virulent subclones capable of causing epidemic disease.
In the new study, Dr. James M. Musser, from Baylor College of Medicine in Houston, and colleagues analyzed strains obtained from 255 patients over an 11-year period in Ontario, Canada. The strains represented peaks in invasive infection that occurred in 1995 and 2000.
The researchers’ findings are published in the July 26th early edition of the Proceedings of the National Academy of Sciences.
The authors identified genotypic differences between the strains and, for the most part, this was due to the acquisition or loss of prophages. Some of the genotypes were associated with rapid population expansion. Moreover, the genotype influenced the character and severity of infection.
In combination with immunologic tests, molecular genetic analysis identified a 4-amino acid duplication in the M protein as playing a key role in epidemic GAS infection.
“Our genome-wide analysis revealed a hitherto unknown complexity of the molecular population genetics of strains of a single GAS M protein serotype,” the authors note. “It is likely that study of other microbial pathogens by the general strategy we used may be a very fruitful line of investigation.”
Source: Proc Natl Acad Sci Early Edition 2004. [ Google search on this article ]
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