Plasmid profile analysis as a tool for characterization of epidemic Shigella sonnei strains.

The usefulness of plasmid profile analysis as a marker to determine the strain number of Shigella sonnei implicated in an epidemic outbreak and its prevalency in our community was studied. We could define two multirresistant strains and determine that the drug resistance was plasmid mediated in both. One strain carried a tra- plasmid which encoded (Sm, Sd)r, the other one carried two tra+ plasmids which encoded (Ap-Cb, Sm, Sd)r and (Sm, Km-Nm, Sd, Tp)r respectively. These strains and some coisolates collected during the later phase of the outbreak carried cryptic plasmids which showed similar electrophoretic mobilities.