title: Antimicrobial resistance pattern and plasmid profile of Salmonella typhi isolated from an outbreak in Tehran province.
abstract: The antimicrobial resistance patterns and plasmid profiles of Salmonella typhi isolates from sporadic cases (n = 33) and an outbreak (n = 48) were compared. Of 28 sporadic drug-resistant isolates, 24 (85.7%) were multiply resistant. The predominant antibiotic resistance pattern was TeCmSmSxTAp, which was also the most common pattern of the outbreak isolates. 13 drug-resistant strains isolated before the outbreak (46.4%) were able to transfer the whole resistance pattern or part of it to Escherichia coli K 12 by conjugation. Although 20 of the sporadic strains contained plasmid DNA, transferable R plasmids were only detected in 13 (65%) of them. Among the outbreak strains, the rate of R plasmid transfer was 92.3%, with only the TeCmSmSxTAp pattern transferred. Plasmid profiling and Hind III endonuclease digestion of plasmid DNA identified a 91.2 megadaltons (Mda) plasmid that was recovered from most of the outbreak isolates and from 4 strains collected before the outbreak. This plasmid coded for TeCmSmSxtAp and transferred the pattern of resistance in toto. The results indicate multidrug-resistant S. typhi as a potential cause of infection in the region.
authors.affiliation: Molecular Microbiology Unit, Pasteur Institute of Iran, Tehran, Islamic Republic of Iran.
authors.forename: A R
authors.initials: AR
authors.lastname: Bahrmand
authors.forename: A A
authors.initials: AA
authors.lastname: Velayati
mesh_terms: D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D006801:Humans; D007492:Iran / Q000453:epidemiology; D010957:Plasmids; D012485:Salmonella typhi / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D012703:Serotyping; D014435:Typhoid Fever / Q000453:epidemiology / Q000382:microbiology*