EPIDEMIOLOGIC EVALUATION BY PCR RIBOTYPING OF SPORADIC AND OUTBREAK-ASSOCIATED STRAINS OF SALMONELLA-ENTERICA SEROTYPE TYPHIMURIUM

Salmonella enterica serotype Typhimurium has a very large diffusion wo rldwide within human and non-human hosts. The simultaneous circulation in the same geographical areas of many bacterial clones requires the use of reliable, reproducible and highly discriminatory typing techniq ues for epidemiological studies.Molecular biological methods, such as plasmid profile analysis, restriction endonuclease digestion of plasmi d and chromosomal DNA and hybridization-based procedures have proven t o be useful tools for strain differentiation. More recently, detection of polymorphisms in the intergenic spacer regions of rRNA genes by po lymerase chain reaction (PCR ribotyping) has been successfully applied to characterize bacterial strains. In this study, PCR ribotyping was performed on 45 epidemiologically related and unrelated strains of S. enterica serotype Typhimurium isolated in northern and southern Italy during 1992. Isolates were simultaneously characterized by traditional ribotyping. Results suggest that PCR ribotyping is a rapid, easy-to-p erform and reproducible typing method able to determine relatedness am ong isolates of this serotype.