Differentiation of Salmonella typhi strains by ribosomal RNA gene restriction patterns

Owing to the limited value of phage typing to determine the epidemiological association of Salmonella typhi (S. typhi) strains isolated from the source of typhoid fever, we analyzed ribosomal RNA (rRNA) gene restriction patterns to differentiate the independently isolated strains of identical phage type. The data showed that the restriction patterns of PstI was most polymorphic among four enzymes (BamHI, EcoRI, PstI, and SmaI) used, which revealed 13 types among 25 strains belonged to 4 phage types, 1 untypable and 2 not-determined strains. Total 25 strains of S. typhi were divided into 15 combination types by the rRNA restriction patterns with three enzymes (BamHI, PstI, and SmaI).