One hundred and twenty Salmonella Typhimurium strains, including 103 isolates from cattle, gathered between 1977 and 1999 in Hokkaido prefecture were analyzed using fluorescent amplified-fragment length polymorphism (FAFLP) to examine the genotypic basis of the epidemic. Among these strains, there were 17 FAFLP profiles that formed 4 distinct clusters (A, B, C, and D). All 12 definitive phage type 104 strains examined belonged to cluster A. Isolates that belonged to cluster A have become increasingly common since 1992 with the increase of bovine Salmonellosis caused by S.Typhimurium. These results indicate that a clonal exchange of S.Typhimurium has taken place since 1992, and show a remarkable degree of homogenecity at the molecular level among contemporary isolates from cattle in this region. Moreover we have sequenced a 142-bp fragment that was identified as a polymorfic marker of strains that belong to cluster A, and also shows homology with a segment of P22 phage. FAFLP is apparently suited for epidemiological typing of S. Typhimurium, and can provide a source of molecular markers useful for studies of genetic variation in natural populations of S. Typhimurium. (Clinical Microbiology Section, Hokkaido Research Station TEL +81-11-851-5226)
References:
Tamada et al.: Molecular typing and epidemiological study of Salmonella enterica Serotype Typhimurium isolates from cattle by fluorescent-amplified length polymorphism fingerprinting and pulsed-field gel electrophoresis. J. Clinical. Microbiol. 39: 1057-1066 (2001)
