Asymptomatic infections with positive throat culture for group A beta-hemolytic streptococci(GABHS) and high antistreptolysin O(ASO) concentration may lead to sequelae such as rheumatic fever or acute poststreptococcal glomerulonephritis. Children with asymptomatic infections were treated with oral penicillin V to evaluate the effectiveness of penicillin treatment on the asymptomatic infections.

Throat culture and ASO concentration analysis were performed against healthy elementary school children. Thirty-six children with positive throat culture for GABHS and ASO concentrations of 400 IU/mL or more were divided into two groups. Twenty-two children were treated with oral penicillin V for 10 days, and the others were not treated. Eradication rate of GABHS and the change of ASO concentration between the two groups were compared after one month later.

Eradication rates of GABHS between treated and untreated children were 91% (20/22) and 50%(7/14) respectively(p<0.05). Children showing elevation of ASO levels more than 100IU/mL were 22%(4/18) in the treated group and 30%(3/10) in the untreated group, while children showing a decrease of more than 200IU/mL in the ASO level were 44% (8/18) and 40%(4/10) respectively.

We confirmed the validity of penicillin treatment because when we treated the asymptomatic children with penicillin V, the GABHS was eradicated effectively. But there was no significant difference of decrease in the ASO levels between the two groups doe to long half-life of ASO or poor compliance. Treatment failure was 22% in terms of elevated ASO levels after penicillin treatment.