[Shigella boydii strains having a provisional serovar isolated from travellers' diarrhea in Tokyo]

Two Shigella strains (85-634 and 94-30) isolated from two sporadic travellers with diarrhea who returning to Tokyo from abroad, did not react to any antisera to Shigella prepared commercially. These strains had the typical biochemical characteristics of S. boydii and were biochemically identical, and were positive in the Serény test and other tests for invasiveness; these indicate that they can cause shigellosis in humans. The results of serological analyses using the antisera to 6 kinds of provisional Shigella serovars, showed that both strains had provisional S. boydii serovar E16553. Although the serovar has been reported by Gross et al in the United Kingdom, this may be the first report in Japan.