Plasmid-mediated multidrug resistance in Salmonella typhi in Kuwait

Multidrug resistant Salmonella typhi infection is common in Kuwait. Between January 1993 and December 1994, 266 strains of S. typhi were isolated from blood of suspected typhoid fever cases attending the Infectious Disease Hospital, Kuwait. Of these, 205 strains were isolated from patients from the Indian sub-continent, 105 (45%) of which showed resistance to one or more drugs; 91 of these resistant strains showed resistance to the oral antimicrobials ampicillin, chloramphenicol, tetracycline and co-trimoxazole (ACTCo). All 266 isolates were sensitive to fluoroquinolones and cephalosporines. The minimum inhibitory concentrations (MIC) for ampicillin, chloramphenicol and tetracycline in resistant strains were >1000 mu g/ml. All 91 strains with ACTCo resistance pattern transferred their resistance to a recipient E. coli strain, whereas none of the remaining 14 strains with different resistance patterns transferred theirs. This paper reaffirms that multidrug resistant S. typhi is quite common in Kuwait and that such resistance is encoded by auto-transferring plasmids.