A follow-up study of throat carriers of streptococci among schoolchildren in Otsu City.

Studies on the prevalence of beta-hemolytic streptococci in throats among primary school children were performed in Otsu City. In the first study, evidence of streptococcal infections was investigated in 41373 children of first grade of all primary schools for the 13 years from 1970 to 1982. An average of 12.2% of the strains isolated belonged to group A. The order of frequency of the other Groups was B, C and G respectively. The most predominant type of Group A streptococci was Type 12. In the second study, evidence of streptococcal infections was investigated in 87 children of the first grade of one primary school for the 5 years from 1977 to 1982. Throat cultures were repeated four times a year during the period of five years. Entire negative throat cultures over a 5-year period were observed in only 4 children. The prevalence of beta-hemolytic streptococci and Group A streptococci in throats were higher than those observed in the first study. The predominant types of Group A were Types 1, 6 and 28, although the relative predominance of these Types varied at different times during 5 years. High serum ASO titers were observed in the children who harbored Type 6 strains of Group A streptococci in throats. In 5 children Group A streptococci were frequently recovered from throats during the study period, and the same type of strains of Group A streptococci were isolated repeatedly.