Molecular subtyping within a single Salmonella typhimurium phage type, DT204c, with a PCR-generated probe for IS200

We report primers and conditions for the generation by PCR of a probe for the DNA insertion element IS200. This probe was shown to be suitable for genotypic subtyping within a single phage type of Salmonella typhimurium. A collection of isolates of DT204c, a phage type implicated in the spread of multiple drug resistance in bovine animals and to man, was analyzed. Three IS200 profiles, corresponding to related chromosomal genotypes were characterized in DT204c. Molecular discrimination within a single phage type of S. typhimurium has general significance for genotypic typing, and for the definition of epidemiological clonality in Salmonella.