Multilocus variable-number tandem repeat analysis of Vibrio cholerae O1 El Tor strains harbouring classical toxin B

International Vaccine Institute, Seoul, Republic of Korea.
Journal of Medical Microbiology (Impact Factor: 2.25). 03/2010; 59(Pt 7):763-9. DOI: 10.1099/jmm.0.017939-0
Source: PubMed


Atypical Vibrio cholerae O1 strains - hybrid strains (strains that cannot be classified either as El Tor or classical biotype) and altered strains (El Tor biotype strains that produce classical cholera toxin) - are currently prevalent in Asia and Africa. A total of 74 hybrid and altered strains that harboured classical cholera toxin were investigated by multilocus variable-number tandem repeat analysis (MLVA). The results showed that the hybrid/altered strains could be categorized into three groups and that they were distant from the El Tor strain responsible for the seventh cholera pandemic. Hybrid/altered strains with a tandem repeat of the classical CTX prophage on the small chromosome were divided into two MLVA groups (group I: Mozambique/Bangladesh group; group III: Vietnam group), and altered strains with the RS1-CTX prophage containing the El Tor type rstR and classical ctxB on the large chromosome were placed in two MLVA groups (group II: India/Bangladesh group; group III: India/Vietnam group).

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Available from: Mohammad Ansaruzzaman, Oct 14, 2015
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    • "No other consensus alleles of MLVA groups matched the current SNP group consensus alleles. However, there were 2 isolates from Africa (M823 and M826) with the profiles 10, 6, -, 7/8, x, x from this study, which matched 2 MLVA profiles of isolates from MLVA group III Vietnam from Choi et al.[19]. These African isolates were collected in 1984 and 1990 while isolates from Choi et al.[19] were collected between 2002–2008. "
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    ABSTRACT: Seven pandemics of cholera have been recorded since 1817, with the current and ongoing pandemic affecting almost every continent. Cholera remains endemic in developing countries and is still a significant public health issue. In this study we use multilocus variable number of tandem repeats (VNTRs) analysis (MLVA) to discriminate between isolates of the 7th pandemic clone of Vibrio cholerae. MLVA of six VNTRs selected from previously published data distinguished 66 V. cholerae isolates collected between 1961-1999 into 60 unique MLVA profiles. Only 4 MLVA profiles consisted of more than 2 isolates. The discriminatory power was 0.995. Phylogenetic analysis showed that, except for the closely related profiles, the relationships derived from MLVA profiles were in conflict with that inferred from Single Nucleotide Polymorphism (SNP) typing. The six SNP groups share consensus VNTR patterns and two SNP groups contained isolates which differed by only one VNTR locus. MLVA is highly discriminatory in differentiating 7th pandemic V. cholerae isolates and MLVA data was most useful in resolving the genetic relationships among isolates within groups previously defined by SNPs. Thus MLVA is best used in conjunction with SNP typing in order to best determine the evolutionary relationships among the 7th pandemic V. cholerae isolates and for longer term epidemiological typing.
    BMC Microbiology 05/2012; 12:82. DOI:10.1186/1471-2180-12-82 · 2.73 Impact Factor
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    • "Using multi-locus variable number tandem repeat analysis, a recent study demonstrated that altered strains from Vietnam are distant from the El Tor prototype strain responsible for the seventh cholera pandemic (Choi et al., 2010). In spite of the minor divergences observed in the present study, the Vietnamese V. cholerae O1 strains with the RS1–CTX prophage (El Tor type rstR and classical ctxB) array on the large chromosome is likely to be more closely related to V. cholerae O1 El Tor variant strains currently circulating in Bangladesh (Nair et al., 2006), India (Goel et al., 2010) and Thailand (Okada et al., 2010). "
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    ABSTRACT: Since 2007, there has been a re-emergence of cholera outbreaks in northern Vietnam. To understand the molecular epidemiological relatedness and determine the antibiotic susceptibility profiles of responsible V. cholerae O1 outbreak strains, a representative collection of 100 V. cholerae O1 strains was characterized. V. cholerae O1 strains isolated from diarrhoeal patients in northern Vietnam between 2007 and 2010 were investigated for antibiotic susceptibility and characterized by using phenotypic and genotypic tests, including PFGE analysis. Ten clinical V. cholerae O1 isolates from Bangladesh and Zimbabwe were included for comparison. The results revealed that all isolates were resistant to co-trimoxazole and nalidixic acid, 29 % were resistant to tetracycline and 1 % were resistant to azithromycin. All strains were susceptible to ampicillin-sulbactam, doxycycline, chloramphenicol and ciprofloxacin and 95 % were susceptible to azithromycin. MIC values did show reduced susceptibility to fluoroquinolones and 63 % of the strains were intermediately resistant to tetracycline. The isolates expressed phenotypic traits of both serogroup O1 Ogawa and El Tor and harboured an rstR El Tor and ctxB classical biotype. Among the outbreak isolates, only a single PFGE pattern was observed throughout the study period. This study shows that multi-drug resistant V. cholerae altered El Tor producing classical CT strains are now predominant in northern Vietnam.
    Journal of Medical Microbiology 03/2012; 61(Pt 3):431-7. DOI:10.1099/jmm.0.034744-0 · 2.25 Impact Factor
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    • "Atypical El Tor strains have been classified into two different groups on the basis of genetic structures of the CTX prophage and RS1 element on each chromosome (Lee et al., 2009; Nguyen et al., 2009). Group 1 strains harbor a tandem repeat of the classical CTX prophage on the small chromosome and Group II strains contain the RS1 and CTX prophage with El Tor type rstR and classical ctxB on the large chromosome (Lee et al., 2009; Choi et al., 2010). All the strains used in this study belonged to Group II strains. "
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    ABSTRACT: Thirty-four Vibrio cholerae isolates collected from a cholera outbreak in Hyderabad, South India were found to belong to serogroup Ol biotype El Tor serotype Ogawa. The genotype of all the isolates was confirmed by PCR assays. All the isolates were found PCR positive for ctxAB, ompW, rflOl, rtxC, and tcpA genes. All the isolates but one harboured rstR ( El Tor ) allele. However, one isolate carried both rstR ( EL Tor ) as well as rstR ( Classical ) alleles. Cholera toxin (ctxB) genotyping of the isolates confirmed the presence of altered cholera toxin B of classical biotype in all the isolates. All the isolates except VCH35 harboured an RS1-CTX prophage array on the large chromosome. The isolate VCH35 contained a tandem repeat of classical CTX prophage on the small chromosome. The clonal relationship among the V. cholerae isolates as carried out by enterobacterial repetitive intergenic consensus sequences PCR, BOX PCR and randomly amplified polymorphic DNA, uniformly showed a genetic relationship among the outbreak isolates. The results of this study suggest that altered El Tor biotype V. cholerae with the classical cholera toxin gene are involved in cholera outbreaks in India.
    The Journal of Microbiology 04/2011; 49(2):280-4. DOI:10.1007/s12275-011-0317-9 · 1.44 Impact Factor
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