Objectives: To examine strain variation amongst Australian isolates of Mycobacterium paratuberculosis.
Design: Pulsed field gel electrophoresis was optimised for differentiation of M paratuberculosis strains, and this typing technique was then applied to a collection of Australian isolates.
Procedure: DNAs from 35 Australian isolates of M paratuberculosis and a UK reference strain were digested with one or other of three restriction endonucleases. The banding patterns obtained after pulsed field gel electrophoresis of the DNA fragments were compared.
Results: The Australian isolates were divided into two groups on the basis of their DNA banding pattern. Both were different from the UK reference strain. Seven isolates from cattle in Victoria and the Northern Territory had the same pattern as five isolates from alpacas in Victoria and Western Australia. Another 20 isolates from cattle in Victoria, Western Australia and the Northern Territory had the same pattern as isolates from two sheep and a goat in New South Wales.
Conclusion: Pulsed field gel electrophoresis was a useful tool for strain typing of M paratuberculosis, and could be used to study the transmission of strains in Australia.