STRAIN TYPING WITH IS200 FINGERPRINTS IN SALMONELLA-ABORTUSOVIS

A collection of Salmonella abortusovis isolates was examined for the p resence of insertion element IS200. All proved to contain three or fou r copies of the element. One IS200 hybridization band of similar to 9 kb was found in all isolates, indicating that all S. abortusovis strai ns carry an IS200 element in similar or identical locations; this band can be potentially useful for serovar identification. S. abortusovis collection isolates from distinct geographic areas were highly polymor phic, suggesting that IS200 fingerprints might provide information on the geographic origin of S. abortusovis strains. Isolates obtained fro m the same geographic area (the island of Sardinia, Italy) were less p olymorphic: all shared three constant IS200 hybridization bands, indic ating that they derive from a single ancestor. Most strains analyzed c ontained an additional copy of IS200 in the variable region of the vir ulence plasmid. Certain Sardinian flocks proved to be infected by only one S. abortusovis strain, while others harbored two strains. Strain typing with IS200 fingerprints proved to be more reliable than plasmid analysis, because the latter yielded a high degree of polymorphism, e ven among isolates from the same flock.