A long-term study of streptococcal infection experienced at an outpatient clinic--outline of patients, diagnoses and serotype of isolates

Abstract

For the purpose of investigating the present condition of streptococcal infection in a typical pediatric outpatient clinic, this observance was undertaken at a private clinic in Matsuyama City, Ehime Pre., Shikoku Island.A total of 2373 cases of streptococcal infection, confirmed bacteriologically, were studied from May, 1975 to March, 1985. Results were as follows:1) Group A streptococci were identified in 96.2% of these cases; 68.1% of the patients had been diagnosed as pharyngitis and 31.2% as scarlet fever.2) Usually two epidemic peaks were observed in each year, which was measured as the period from the beginning of April to the end of the following March. One was a small peakoccuring in early summer (mainly May, June and July) and the other was a large peak occuring in winter (Oct., Nov. and Dec.). From the analysis of age distribution of the patients and serological types of group A streptococcal isolates, it seems that the typical epidemic is caused by onetype of streptococcus. The largest number of cases is seen in the winter, because of the patients' lowered resistance, andthe beginning of the school year in April exposes susceptible youngsters toinfection, resulting in a small epidemic peak in early summer.3) Prevalent serotypes of group A streptococci were types 12, 4 and 1. It was observed that the peak frequency of isolation could be found for each strain every 5 to 6 years.4) T-typable rate of group A streptococcal isolates was 99.6% and M-typable rate was 67.9%. Coincidence between T and M types was as follows; Type 3; 97.9%, Type 6; 97.7%, Type 4; 92.4%, Type 1; 91.3%, Type 12; 79.9%.5) M12 strain had a more statistically significant tendency to induce scarlet fever than did the other types of group A streptococci.6) 12.9% of the patients in this study were confirmed to be reinfected cases. It is speculatedthat this result suggests that the use of antibiotics in the early stages of infection surpressed the production of antibodies and was responsible for the later reinfection.