Epidemiological Study on Streptococcal Infectious Diseases and Group A Streptococci in Akita: Classification of 21 Serotypes of Group. A Streptococci

The present study was undertaken to obtain quantitative data on the recent prevalence of streptococcal infectious disease accompanied with rash, rheumatic fever and acute nephritis in Akira Prefecture, and to classify epidemiologically 21 serotypes of group A streptococci into some classes. The obtained results were summerized as follows. 1. It was estimated to be approximately 25, 143, 495 and 1, 192 patients (per one year) with streptococcal infectious disease accompanied with rash, rheumatic fever and acute nephritis, respectively, based on the data of infectious diseases surveillance and control programs in Akita Prefecture during a 2 year period between 1978 to 1979. While morbidity rates of scarlet fever in this prefecture, 1976 to 1979, revealed 22.7 to 28.3 per 100, 000 of population. 2. From 800 patients with various streptococcal infections, 216 strains and 11 serotypes of group A streptococci were isolated during the period 1976 through 1979. Of these serotypes, 28.7% was type T 4 and 28.2% type T 12. 3. Of 469 persons in 4 regions of this prefecture, 272 (58%) possessed type specific T antibodies against more than one serotype of group A streptococci. The rate of one or more T antibody positive was considerably low in the group of infants under age 3 years, but increased abruptly with age and came to 85.7% at the group of age 10-12 years. The further detailed test revealed that predominant serotypes of detected antibodies against the organisms were T 12, 4, 44, and 14 among 20 detected different serotypes, representing 35.6%, 25.6%, 23.2% and 21.5% in positive rate, respectively. It appeared to be regional differences in the rates of antibody positive and the serotypes of antibodies. It was also suggested that the rates of T antibody positive correlated inversely with the morbidity rates of scarlet fever in the 4 regions. 4. Based on the epidemiological study with positive rates of individual type specific T antibodies and with detection rates of individual serotypes of the isolates from patients with various streptococcal infections, 21 serotypes of group A streptococci were classified into seven classes (type T 2, 8, 9, 25 and Imp. 19; type T 11, 14, 27, 44 and 49; type T 3 and 23; type T 5, 13 and 28; type T 1 and B 3264; type T 6 and 22; type T 4 and 12). On the basis of serotype distribution (ratio) of the detected T antibodies and the isolated streptococci, it was also tried to estimate individual pathogenic indexes of 21 tested serotypes