AN EPIDEMIOLOGIC-STUDY OF VIBRIO-CHOLERAE O1 IN THE AUSTRALIAN ENVIRONMENT BASED ON RIBOSOMAL-RNA GENE POLYMORPHISMS

Since 1977, Vibrio cholerae O1 has been isolated from the Australian a quatic environment and periodically cholera cases have occurred follow ing 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 molec ular typing methods were employed, In this paper we report the analysi s of the 180 Australian isolates (10 clinical and 170 environmental) u sing ribotyping. Seven ribotype patterns were observed among the Austr alian inaba isolates, 2 of which included all clinical inaba isolates and 84% environmental inaba isolates collected from 9 rivers and creek s in eastern Australia during an 8-year period, Isolates from epidemio logically related clinical cases: asymptomatic household contacts and sewage were indistinguishable. The ogawa isolates were more diverse, w ith 9 ribotypes observed among 24 isolates from 8 rivers during the sa me period. Ribotype patterns were not shared between the serotypes wit h the exception of one ogawa a isolate which could be distinguished us ing PFGE. Ribotyping has been useful in confirming an association betw een epidemiologically related clinical isolates and the aquatic enviro nment and the persistence of several clones of the O1 serovar in the A ustralian environment during an 8-year period.