GENOMIC RELATIONSHIPS BETWEEN SELECTED PHAGE TYPES OF SALMONELLA-ENTERICA SUBSP ENTERICA SEROTYPE TYPHIMURIUM DEFINED BY RIBOTYPING, IS200 TYPING AND PFGE

The genomic relationship between isolates representing 17 definitive p hage types (DTs) of Salmonella enterica subsp. enterica serotype typhi murium (S. typhimurium) were analysed using three different typing met hods: IS200 typing using the restriction enzymes EcoRI and PvuII, ribo typing using SmaI and EcoRI, and PFGE using XbaI. These methods were u sed to study four DTs in greater detail; in all 18 (DT 49), 10 (DT 110 ), five (DT 120) and seven (DT 135) isolates were studied. The combine d data generated two large clusters, which could be divided into five groups. Within the first cluster, a close similarity was indicated bet ween isolates of the following phage types: group A - DTs 44, 49, 135 and 204c, with DT 9 distantly related; group B - DTs 95 and 99; and gr oup C-DTs 104a, 110 and 120. The other large cluster contained group D - DTs 10, 20 and 146, with DT 12 distantly related, and group E - DTs 69, 103 and 153. The same grouping was observed by principal componen t analysis, but a minimum spanning tree linked DT 12 to group E and no t group D in this analysis. Among the typing methods used, IS200 gave the best representation of the overall similarity between the S. typhi murium isolates. Five different IS200 profiles were obtained among iso lates belonging to DT 49. Only one profile was observed within each of the phage types DT 110, 120 and 135. All isolates within each of thes e four phage types were of one ribotype. Isolates of DT 49 showed four PFGE patterns, while one pattern was present within isolates of the t hree other phage types. Members of these four phage types were found t o be clonally related as they formed tight subclusters separated from isolates of other phage types.