Phage type 193 of Salmonella typhimurium contains different chromosomal genotypes and multiple IS200 profiles

The common phage type 193 of Salmonella typhimurium was analyzed with respect to molecular markers of chromosomal genotype. Three profiles of the 16S rRNA genes and seven profiles of the DNA insertion element IS200 were found among ten representative strains of DT193. The IS200 profiles found within this single phage type were highly diverse, confirming that DT193 is a composite phage type containing several distinct clones and hybrid lines. IS200 profiling is thus appropriate both for primary strain discrimination, and for subdivision within certain phage types of S. typhimurium, such as DT193. This rapid molecular definition of clonality will be useful for the epidemiological investigation of food poisoning outbreaks.