Molecular analysis of multi-drug resistant Salmonella typhi from urban paediatric population of Bangladesh.

The prevalence and genetic basis of resistance of multi-drug resistant (MDR) S typhi strains from an urban paediatric population was determined. Blood cultures performed on 109 cases of suspected typhoid fever yielded 30(27.5%) S typhi isolates. Of these, 20(67%) S typhi isolates were resistant to the common antimicrobials used in Bangladesh, eg, chloramphenicol, ampicillin, cotrimoxazole, streptomycin and tetracycline, while 6(20%) isolates were resistant only to streptomycin. However, all the isolates were sensitive to fluquinolones and cephalosporins. Molecular analysis demonstrated that all MDR strains possessed a single large transferable 98 MDal plasmid. On conjugation, chloramphenicol, ampicillin and cotrimoxazole resistance was transferred from MDR strains to E coli K-12. Restriction endonuclease analysis of plasmid DNA showed similar digest profiles of all 5 selected donors and their transconjugants. This trend of increasing resistant strains of S typhi, especially by the transferable plasmid is of major public health concern.