A fatal case of cholera caused by O1 El Tor serotype Ogawa occurred in Aichi Prefecture, Japan in 1995. The patient was identified locally, but the route of the infection was unknown. The causative isolate and 38 other domestic and imported O1 isolates, obtained between 1984 and 1997, were analysed by prophage typing, antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE). This was done to determine whether the isolate from this case differed from others associated with either mild cholera infections or asymptomatic carriage, and to elucidate the route of infection. Cholera toxin (CT) from 37 toxigenic isolates was assayed semi-quantitatively. The 39 isolates were divided into 12 temporary types in accordance with the results of the three typing techniques. The isolate from the fatal infection and nine other isolates were classified as temporary type IV. No difference in CT production was found between the isolate from the fatal case and the other 36 toxigenic isolates. Taken together, it is unlikely that a O1 isolate of distinguishable type was responsible for the fatal illness. Temporary type IV isolates were frequently present in both domestic and imported cases from 1994 to 1997 in Aichi, but they did not emerge before 1993. These results suggest that a new clone was introduced after 1993 from overseas and then disseminated into Aichi, and this may have been an important step in triggering the fatal case of cholera.


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