A Vibrio cholerae O139 strain was isolated from a cholera patient in August 1997 in Kaohsiung County, Taiwan. This was the first
case of V. cholerae O139 emerging in Taiwan. An epidemiological study showed that the infectious source was turtle eggs. One clinical
isolate and fourteen isolates from environmental specimens of the turtle farm were collected. From all isolates, the genes encoded for
cholera toxin (ctxA and ctxB) and for toxin-coregulated pili genes (tcpA and tcpI) were specifically amplified by polymerase chain reactions.
In pulsed-field gel electrophoresis (PFGE) studies, these isolates were categorized to five subtypes using SfiI restriction digestion;
whereas three distinct subtypes were identified when NotI was used for digestion. The banding pattern of the clinical isolate in PFGE only
differed by 1-3 bands from those of the environmental isolates regardless of the restriction enzyme used. The Dice coefficients were found
to be in the range of 0.88-1.0 and 0.87-1.0, respectively, by using SfiI and NotI for the subtyping. When these isolates were analyzed by
plasmid profile analysis, the profile pattern of the clinical strain was identical to 12 of the 14 environmental strains. Based on these results,
it was concluded that the fifteen strains studied were descended from the same origin, with the clinical isolate originated from the environmental
isolates. The data suggests that the molecular subtyping is a powerful tool for tracing and verifying the infectious sources of V.
cholerae cases.