DISTRIBUTION AND HYBRIDIZATION PATTERNS OF THE INSERTION ELEMENT IS900 IN CLINICAL ISOLATES OF MYCOBACTERIUM-PARATUBERCULOSIS

Reference strains and 31 clinical isolates of M. paratuberculosis, mai nly from goats, were analysed for restriction fragment length polymorp hism (RFLP). Restriction digests of bacterial DNA were hybridized with a repetitive insertion sequence, IS900, to obtain banding patterns fo r comparison of strains. Twenty-five of the 31 field-strains hybridize d with IS900, and five hybridization patterns were identified. It was not possible to identify specific patterns for goat strains of M. para tuberculosis. Four hybridization patterns were similar, whereas the fi fth pattern of a sheep strain diverged considerably in position and nu mber of bands. Six goat strains failed to hybridize with IS900, and th e absence of IS900 was verified by the polymerase chain reaction and h ybridization with an oligonucleotide probe. The six IS900-negative goa t strains had diverging phenotypic properties, and the identification of these strains is discussed. The present study shows that M. paratub erculosis strains infecting goats are genetically similar to cattle st rains and that IS900 is a specific genetic element for identification of M. paratuberculosis.