DISTINCTIVE IS200 INSERTION BETWEEN GYRA AND RCSC GENES IN SALMONELLA-TYPHI

While probing the vicinity of ompC, a copy of the IS200 insertion elem ent was found between the gyrA and rcsC genes of Salmonella typhi, the causal agent of typhoid fever, This distinctive feature was conserved throughout 63 S. typhi isolates of different geographical origins and was absent from 46 other Salmonella serotypes, including those most a ssociated with human infections, as well as from 19 other enteric bact eria, Furthermore, the location of this IS200 copy corresponds to a co nstant band, present throughout the 14 PstI S. typhi IS200 fingerprint s, encompassing several Vi phage types. Interestingly, an apparently u nrelated serotype not frequently associated with human disease, Salmon ella weltevreden, contained an IS200 copy at the same position, althou gh if was accompanied by an additional segment of cryptic DNA, On the basis of these findings, PCR assays were designed for molecular typing of S. typhi, and these are potentially useful in studying the epidemi ology of typhoid fever.