An epidemiological study of Vibrio cholerae O1 in the Australian environment based on rRNA gene polymorphisms

Since 1977, Vibrio cholerae O1 has been isolated from the Australian aquatic environment and periodically cholera cases have occurred following exposure to these environments. To study the relationships between clinical isolates and environmental isolates from rivers and aquatic life, widely distributed throughout the country, a wide range of molecular typing methods were employed. In this paper we report the analysis of the 180 Australian isolates (10 clinical and 170 environmental) using ribotyping. Seven ribotype patterns were observed among the Australian inaba isolates, 2 of which included all clinical inaba isolates and 84% environmental inaba isolates collected from 9 rivers and creeks in eastern Australia during an 8-year period. Isolates from epidemiologically related clinical cases, asymptomatic household contacts and sewage were indistinguishable. The ogawa isolates were more diverse, with 9 ribotypes observed among 24 isolates from 8 rivers during the same period. Ribotype patterns were not shared between the serotypes with the exception of one ogawa isolate which could be distinguished using PFGE. Ribotyping has been useful in confirming an association between epidemiologically related clinical isolates and the aquatic environment and the persistence of several clones of the O1 serovar in the Australian environment during an 8-year period.