ABSTRACT
Objective To evaluate the capability of multilocus variable-number tandem-repeat ( VNTR) analysis ( MLVA) and pulsed-field gel electrophoresis ( PFGE) for genotyping Salmonella enterica serovar Typhi (S.Typhi) isolates.Methods Five polymorphic VNTRs (SAL02,SAL11,SAL16,SAL20, and TR4699 ) that were observed in S.Typhi strains from previous studies were selected to establish MLVA . Twenty-one epidemiologically unrelated S.Typhi strains that were isolated from Shenzhen ,China from 2002 to 2007 were genotyped by the established MLVA , and the results were compared with those by PFGE . Results The Simpson′s index of diversity ( D value ) for all five different VNTRs ranged from 0.838 to 0.943 .A total of 19 MLVA profiles and 19 PFGE profiles were found , respectively .The D value for both MLVA and PFGE were 0.99 and the test results from two analyses were identical .Conclusion The five polymorphic VNTRs analysis could be used as an alternative typing scheme for epidemiologic investigation of S.Typhi infection .
ABSTRACT
BACKGROUND: Clostridium difficile infection (CDI) has markedly risen and is associated with hypervirulent ribotype 027 outbreaks in North America and Europe since 2003. The aims of this study were to determine the prevalence of ribotype 027 among C. difficile isolates in Korea, to characterize the ribotype 027 isolates, and to determine the clinical severity of CDI in patients infected with these isolates. METHODS: A total of 1,251 isolates of C. difficile recovered from stool specimens of suspected CDI patients at two tertiary-care hospitals and one commercial laboratory between 2002 and 2009. Genes for toxin A (tcdA), toxin B (tcdB), and binary toxin (cdtA and cdtB) were detected by PCR. Mutation in the tcdC gene was detected by sequencing after PCR amplification. For molecular genotyping, we performed PCR-ribotyping, pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat analysis (MLVA). Minimum inhibitory concentrations of moxifloxacin were determined using Etest strips (AB bioMerieux, Sweden). RESULTS: We identified 7 isolates as ribotype 027. These isolates had the same tcdC mutation as the epidemic strain, and 6 of them were resistant to moxifloxacin. The isolates were categorized into 3 different PFGE types and 7 different MLVA types. All the 7 cases had occurred sporadically. CONCLUSIONS: C. difficile ribotype 027 is uncommon, but it has emerged in Korea. The spread of this ribotype should be closely monitored in order to avoid an outbreak of CDI in Korea.