Epidemiological Surveillance of Group A Streptococci Isolated from School Children Using emm Genotyping

Kim, Sun Joo

Abstract

BACKGROUND: Group A streptococci (GAS), the most common cause of bacterial pharyngitis, can be spread by interpersonal contact. While T typing is useful for screening, it does not completely identify organisms for epidemiological studies. The M protein is the most important virulence marker but has a drawback for epidemiological studies in that it is difficult to maintain the more than 80 necessary kinds of sera. The emm gene, which encodes the M protein, has variable sequences at the 5' N terminus, and emm genotyping using PCR and automatic sequencing has been reported lately.
METHODS
Beta-hemolytic streptococci (BHS) were isolated from the throats of elementary school children in Jinju. T typing and emm genotyping was performed and compared with the T and M typing results of 1995.
RESULTS
One hundred seventeen (20.1%) from 581 children yielded BHS, of which 83.8% were group A. T non-typeable strains were the most common (43.9%) and T12 was next (27.6%). The emm 12 was most frequent (33.7%), and emm 75 (10.2%), emm 18 (9.2%), emm 22 (8.2%), and emm 1 (7.1%) were relatively common. emm 2, 18, 50 and 75 were newly recognized. The isolation rate of BHS was 32.4% of which 57.1% was group A in 1995. T12 (44.7%) and T28 (13.2%) were the most common, and M12 (26.3%) and M28 (10.5%) were frequently identified in 1995.
CONCLUSIONS
GAS was relatively common in school children. The distribution of the T antigen did not change significantly except for the T non-typeable since 1995. emm genotypes were diverse and emm 2, 18, 50 and 75 were newly recognized. Continuous microbiologic and epidemiological surveillance for GAS should be conducted in the community.