Insertion sequence IS200 fingerprinting of Salmonella typhi: an assessment of epidemiological applicability

When Pst I-generated digests of genomic DNA from each of the type strains of 49 of the Vi phage types of Salmonella typhi were probed with a PCR-amplified IS200 gene probe, all strains were found to possess at least 11 IS200 elements carried on fragments in the range 24.2-1.2 kb. Fourteen fingerprints were identified but two patterns designated IS200Sty1 and IS200Sty2 predominated. In one strain, a plasmid-mediated IS200 element was identified. When IS200 fingerprinting was applied to epidemiologically-unrelated strains of S. typhi isolated in Ecuador, 3 patterns were identified in 10 strains belonging to 9 different phage types. It is concluded that Vi phage typing remains the method of choice for the primary differentiation of S. typhi but that IS200 fingerprinting may be of limited use in laboratories which do not have access to phage typing.