Long-term observations on type distribution of clinical isolated of beta-hemolytic streptococci in Sapporo. I. T-type distribution of group A hemolytic streptococci during the thirty one-year period between 1969 and 1999

Abstract

During the thirty one-year period between 1969 and 1999, a total of 6,876 strains of group A streptococci isolated in Sapporo City General Hospital were classified by T-agglutination method. This research consisted of 5,866 strains of scarlet fever-patients (scarlet fever-strains), 450 of child-patients (child-strains), 141 of adult-patients (adult-strains) and 409 strains of the indistinct. The results were summarized as follows: 1. Total of 6,866 strains were classified to sixteen kinds of T-types such as T12 (44.1%), T4 (21.7%), T1 (9.2%), T6 (4.4%), T3 (2.8%), T22 (2.1%), T18 (1.9%), T28 (1.6%) & others. This pattern of type distribution, three prevailing types of T12/T4/T1, have been reported in other areas generally. But original increase of isolation rates of strains of some T-types as T6, for example, also appeared in Sapporo. 2. Long-term observations demonstrated that the isolation rates of individual T-type, especially T4 or T1, had been forming a small epidemic-wave having a 4 to 8 year-interval and these of type T3 or type T6 on the other hand were repeating sudden prevalence every several years. 3. The isolation rates of type T12 or type T4 in scarlet fever-strains, were significantly higher than in child-strains or adult-strains. It was shown that Type T1 was distributed widely irrespective of patient-group and age-group. It was also characteristic to be distributed to many T-types in adult-strains.