Annual surveys were carried out on about 200, 000 persons working with eating facilities and catering services in Tokyo every year during a five-year period beginning in 1959 in order to detect etiological organisms of estival intestinal diseases. In these surveys, dysentery bacilli were detected and isolated strains examined for sensitivity to antibiotics. As a result, the following trend was observed during this quinennial period.
1. The rate of dysentery bacilli from healthy persons was 0.32 per cent in 1959 and decreased gradually to 0.14 per cent in 1962 and 0.18 per cent in 1963. It was reduced to half in these five years.
2. The predominant types of isolated organisms were flex. 2a, 2b, and 3a and sonnei in 1959, occupying as much as 80 per cent of the total organisms detected. They consisted of three types, flex. 2a, sonnei, and 3a, in 1963, amounting to more than 80 per cent of the total organisms isolated.
3. The rate of drug-resistance of these isolated strains was one-third - one-half that of the strains derived from patients. This rate, which was 4.0 per cent in 1959, increased about four times in five years, reaching 14.6 per cent in 1963. It is of particular interest to note that such strains as resistant to three different antibiotics increased in number among the resistant strains isolated in later years. Such triple resistant strains occupied 52 per cent of the whole resistant strains detected in 1959 and 70 per cent of those isolated in 1963.
Antibiotic-resistant strains detected from healthy subjects have been even increasing in number. So have been strains resistant to three different antibiotics found among them. This constitutes an important problem in the control of dysentery.