Background: T typing has been used as a screening test for epidemiologic studies of group A streptococci (GAS) infections or carriers, and M typing has been performed for virulence studies. However, M typing is difficult to perform in routine laboratories. Recently, genotyping of the emm gene, which encodes the M protein, has become available. We investigated which T antigen is closely associated with a certain emm genotype.

Methods: GAS were collected from the children in Jinju who were asymptomatic carriers (N=349) or had acute pharyngitis (N=122) during the 3 year-period from 2002 through 2004. T typing was performed by a slide aggulutination, and emm genotyping by PCR and DNA sequencing.

Results: More than 90% of T1, T3, T6, T12, T25, and T5/27/44 antigens were associated with emm1, emm3, emm6, emm12 and 22, emm75, and emm44/61 genotypes, respectively; however, other T antigens, such as T2, T4, T7, T11, and B3264, were not associated with any particular emm genotypes.

Conclusion: Several T antigens are so closely associated with particular emm genotypes that one could predict emm genotypes based on the result of T typing. (Korean J Clin Microbiol 2006;9(1):18-23)