Colicine Type of Shigella Sonnei Isolated from Mass Outbreak Cases in Yamaguchi Prefecture and its Neighboring Prefectures

Abstract

The most characteristic change in the recent epidemiological aspects of bacillary dysentery in this country is the prevalence of Shigella Sonnei as causative agents. The trend has been seen since 1962 and the percentage of them in Shigella isolations throughout the country has surpassed 70%, most recently. Mass outbreaks due to Shigella sonnei have also been increasing year by year. In Yamaguchi prefecture, there were as many as 21 bacillary dysentery epidemics in 1966, all of which were due to Shigella Sonnei.
In these circumstances in this country, interest in colicine typing of Shigella sonnei has increased rapidly and as the reports available accumulated, the reliability of this technique as an epidemiological marker has become widely recognized.
In this paper, the authors presented the results of colicine typing done by Abbott and Shannon's method on 1, 028 strains of Shigella sonnei ; 788 strains of them were those originated from 31 epidemic occasions occurring in Yamaguchi prefecture from July, 1963 to June, 1966; the remaining 240 were those isolated in 1966 in its neighboring prefectures, namely Tottori, Shimane, Ehime, Tokushima and Ooita prefecture, and sent to this institute.
It was proved that most of these strains belonged to either of two groups; one is a group compounding Type 4 and Type 14, the other a group compounding Type 6 and Type 11. It, however, is hard by usual technique to separate either Type 4 from Type 14 or Type 6 from Type 11. Then, in order to distinguish them, the authors applied Fredericq's agar stabbed technique Using three mutants of Escherichis coli K12 (Row/E, Row/I, K 12-30/I) as additional indicators in accordance with Okada's advocacy.
In 31 epidemics in Yamaguchi prefecture, 12 were proved caused by Type 14, 7 were by Type 0, 6 were by Type 6, 3 were by Type 4 and one was by Type 13; the remaining two occasions were found caused by mixed two types, Type 0 and Type 14 in one and Type 0 and Type 6 in another. There found some colicine types other than types above mentioned, though each being in a small number.
In strains sent from the neighboring prefectures, Type 14 maintained the most superior position in number, Type 6 ranked next, and Type 2 and Type 0 followed in order. Besides, a small number of Type 4, 5, 3, 8, 13 and 3A were also found.