Molecular typing of Salmonella serotype Thompson strains isolated from human and animal sources

One-hundred-and-thirteen isolates of Salmonella serotype Thompson from dive rse sources in seven countries were characterized by PvuII ribotyping and I S200 fingerprinting. Ten PvuII ribotypes were observed. The predominant Pvu II ribotype 1 represented a major clone of world-wide distribution but was not found in Australia; PvuII ribotypes 2 and 3 represented minor clones. H incII ribotyping discriminated subtypes within PvuII ribotype 1: HincII rib otype 1 was distributed widely but HincII ribotype 2 was found mainly in Sc ottish isolates. None of 101 isolates of PvuII ribotypes 1-3 contained copi es of IS200. All 12 isolates of PvuII ribotypes 4-10 were from Australia an d 7 of them contained copies of IS200 of 5 different profiles. These result s suggest the existence of at least two lineages of Salmonella Thompson wit h a different geographical distribution. The finding that most isolates fro m man and poultry in Scotland belonged to the same ribotype (PvuII 1/HincII 2) and were IS200-negative suggests that poultry is an important source of human infection in Scotland.