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
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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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    • "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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    • "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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