title: Emergence of multidrug-resistant Salmonella enterica serovar typhi in Korea.
abstract: A chloramphenicol-resistant strain of Salmonella enterica serovar Typhi was first noted in Korea in 1992, when a resistant isolate was detected in a returned traveler. Continued isolation of multidrug-resistant (MDR) strains thereafter in other settings prompted a retrospective analysis of laboratory records and phenotypic and genotypic analyses of 12 chloramphenicol-resistant isolates. Among these, one isolate was resistant only to chloramphenicol, and the other isolates were also resistant to ampicillin and co-trimoxazole. MDR was transferred by conjugation from 9 of the 11 isolates. PCR showed that all isolates had an incompatible group HI1 plasmid, and oriT was detected in 10 isolates, which included strains with an unsuccessful transfer of resistance. All of the ampicillin-resistant isolates had a beta-lactamase band of pI 5.4 and bla(TEM) alleles. A PCR amplicon from an isolate showed that the sequences were identical to those of bla(TEM-1), suggesting that all isolates had a TEM-1 beta-lactamase. All isolates had class 1 integrons: 10 isolates had integrons of ca. 1.2 kb with dhfr7 gene cassettes, and 1 isolate had an integron of ca. 2.3 kb with aacA4 and bla(OXA-1)-like gene cassettes. The pulsed-field gel electrophoresis patterns of 7 of 11 MDR isolates were identical and indistinguishable from those reported for isolates in India and Indonesia. In conclusion, some of the MDR strains in Korea are related to those in other Asian countries. Susceptibility testing became necessary for selection of antimicrobial agents for the optimal treatment of patients with the emergence of MDR Salmonella serovar Typhi in Korea.
authors.affiliation: Department of Laboratory Medicine, Yonsei University College of Medicine, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea.
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.forename: Jong Hwa
authors.initials: JH
authors.lastname: Yum
authors.forename: Young Sik
authors.initials: YS
authors.lastname: Lim
authors.forename: Hyun Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Bok Kwon
authors.initials: BK
authors.lastname: Lee
authors.forename: Yunsop
authors.initials: Y
authors.lastname: Chong
mesh_terms: D000483:Alleles; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002701:Chloramphenicol / Q000494:pharmacology; D003227:Conjugation, Genetic / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D007525:Isoelectric Focusing; D007723:Korea / Q000453:epidemiology; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012485:Salmonella typhi / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D014435:Typhoid Fever / Q000453:epidemiology* / Q000382:microbiology*; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D002701:Chloramphenicol; D001618:beta-Lactamases