Novel ctxB variants of Vibrio cholerae O1 isolates, China

Ping, Zhang; Zhou, Haijian; Kan, Biao; Wang, Duochun

doi:10.1016/j.meegid.2013.08.004

Cited by 17 publications

(8 citation statements)

References 31 publications

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“…Other ctxB variants have been reported in association with O139 strains in Bangladesh (21) and El Tor O1 strains in China (17). Here, the ctxB of our SC2008 strain matched that from previously reported Chinese environmental O1 El Tor isolates (17). Factors which select for ctxB gene variants are not well understood.…”

Section: Discussionsupporting

confidence: 68%

“…Genotypes 1, 2, and 3 have been linked with O1 and O139 V. cholerae isolates (19): genotype 3 is responsible for the 7th pandemic, genotype 2 has been found only in El Tor isolates from Australia, and the first report of an atypical El Tor biotype that consisted of classical ctxB (genotype 1) and emerged between 1991 and 1994 in Matlab, Bangladesh, was published in 2002 (20). Other ctxB variants have been reported in association with O139 strains in Bangladesh (21) and El Tor O1 strains in China (17). Here, the ctxB of our SC2008 strain matched that from previously reported Chinese environmental O1 El Tor isolates (17).…”

Section: Discussionmentioning

confidence: 99%

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Distribution of Virulence-Associated Genes and Genetic Relationships in Non-O1/O139 Vibrio cholerae Aquatic Isolates from China

Li³

et al. 2014

Appl Environ Microbiol

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e Non-O1/O139 Vibrio cholerae is naturally present in aquatic ecosystems and has been linked with cholera-like diarrhea and local outbreaks. The distribution of virulence-associated genes and genetic relationships among aquatic isolates from China are largely unknown. In this study, 295 aquatic isolates of V. cholerae non-O1/O139 serogroups from different regions in China were investigated. Only one isolate was positive for ctxB and harbored a rare genotype; 10 (3.4%) isolates carried several types of rstR sequences, eight of which carried rare types of toxin-coregulated pili (tcpA There was no correlation between the prevalence of putative virulence genes and that of CTX prophage or TCP genes, whereas there were correlations among the putative virulence genes. Further multilocus sequence typing (MLST) placed selected isolates (n ‫؍‬ 70) into 69 unique sequence types (STs), which were different from those of the toxigenic O1 and O139 counterparts, and each isolate occupied a different position in the MLST tree. The V. cholerae non-O1/O139 aquatic isolates predominant in China have high genotypic diversity; these strains constitute a reservoir of potential virulence genes, which may contribute to evolution of pathogenic isolates. Vibrio cholerae is the causative agent of cholera, a life-threatening diarrheal disease. Of the more than 200 known V. cholerae serogroups, only O1 and O139 are associated with epidemic and pandemic cholera (1). V. cholerae strains in other serogroups (non-O1/O139 V. cholerae) are often nonpathogenic or associated with only mild illness (2). However, depending in part on the virulence factors which they carry, they have been linked with more-severe, cholera-like illness and have been associated with sporadic cases and outbreaks of gastroenteritis and extraintestinal infections in both developing and developed countries (2-7).Two genetic elements associated with virulence in pathogenic O1 and O139 V. cholerae are a lysogenic filamentous bacteriophage (CTX prophage), which encodes cholera toxin (CT) (8), and the toxin coregulated pilus (TCP) pathogenicity island, which encodes factors involved in intestinal colonization. The CTX prophage uses TCP as a receptor, allowing V. cholerae infection and prophage integration into the bacterial chromosome (8), resulting in the emergence of new toxigenic strains. Non-O1/O139 strains that carry the genes for the CTX prophage and TCP and express CT have been linked with occurrences of severe disease. Other factors that have been associated with virulence include heat-stable toxin (NAG-ST) and hemolysin (Hly) (9). Recently, several novel virulence mechanisms, including a type III secretion system (TTSS) and a type 6 secretion system (T6SS), have been identified in non-O1/O139 isolates (10, 11).Non-O1/O139 V. cholerae strains are naturally present in aquatic ecosystems, such as rivers, estuaries, and coastal waters (4, 12). We hypothesize that carriage of these and other virulence factors by non-O1/O139 strains creates an environmental reservoir of criti...

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Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Distribution of Virulence-Associated Genes and Genetic Relationships in Non-O1/O139 Vibrio cholerae Aquatic Isolates from China

Li³

et al. 2014

Appl Environ Microbiol

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“…Furthermore, variant ctxB genotypes were found in O1 El Tor isolates in Haiti (37) and the O139 isolates during 1998 to 2005 in Bangladesh (38). Recently, we found that the ctxB-CL type of V. cholerae O1 El Tor appeared in 1992 and replaced the prototype El Tor from 2002 to 2010 in China (39), with other El Tor variants that differed from known ctxB genotypes also identified (40). Interestingly, we found no evidence of a shift to the ctxB-CL type among Chinese O139 isolates included in this study.…”

Section: Discussionmentioning

confidence: 85%

A Molecular Surveillance Reveals the Prevalence of Vibrio cholerae O139 Isolates in China from 1993 to 2012

et al. 2014

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bVibrio cholerae serogroup O139 was first identified in 1992 in India and Bangladesh, in association with major epidemics of cholera in both countries; cases were noted shortly thereafter in China. We characterized 211 V. cholerae O139 isolates that were isolated at multiple sites in China between 1993 and 2012 from patients (n ‫؍‬ 92) and the environment (n ‫؍‬ 119). Among clinical isolates, 88 (95.7%) of 92 were toxigenic, compared with 47 (39.5%) of 119 environmental isolates. Toxigenic isolates carried the El Tor CTX prophage and toxin-coregulated pilus A gene (tcpA), as well as the Vibrio seventh pandemic island I (VSP-I) and VSP-II. Among a subset of 42 toxigenic isolates screened by multilocus sequence typing (MLST), all were in the same sequence type as a clinical isolate (MO45) from the original Indian outbreak. Nontoxigenic isolates, in contrast, generally lacked VSP-I and -II, and fell within13 additional sequence types in two clonal complexes distinct from the toxigenic isolates. In further pulsed-field gel electrophoresis (PFGE) (with NotI digestion) studies, toxigenic isolates formed 60 pulsotypes clustered in one group, while the nontoxigenic isolates formed 43 pulsotypes which clustered into 3 different groups. Our data suggest that toxigenic O139 isolates from widely divergent geographic locations, while showing some diversity, have maintained a relatively tight clonal structure across a 20-year time span. Nontoxigenic isolates, in contrast, exhibited greater diversity, with multiple clonal lineages, than did their toxigenic counterparts.

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“…Other atypical El Tor isolates have been reported in other countries in Asia (7,8) and Africa (9,10), as well as in Mexico (11). Previously, we identified three novel El Tor variants from China in which the ctxB genotype was different from known genotypes (12). These results suggested that there were variants in China; however, the traits have not been investigated.…”

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confidence: 82%

The Seventh Pandemic Vibrio cholerae O1 El Tor Isolate in China Has Undergone Genetic Shifts

Zhang

Liang

et al. 2014

J Clin Microbiol

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Vibrio cholerae is the causative agent of the life-threatening diarrheal disease cholera (1). Seven distinct pandemics of cholera have been recorded since the first pandemic in 1817. The sixth pandemic, and presumably the earlier pandemics, were caused by V. cholerae O1 of the classical biotype. The current seventh pandemic, which originated in Indonesia in 1961, is the most extensive in geographic spread and duration, and the causative agent is V. cholerae O1 of the El Tor biotype. In 1992, an outbreak of O139 cholera emerged in the coastal areas of India and then spread to many countries in Asia (2, 3).The classification of the classical and El Tor biotypes of V. cholerae O1 is based on several phenotypic and genetic traits. The phenotypic traits include chicken erythrocyte agglutination (CCA), Voges-Proskauer (VP) test results, susceptibility to polymyxin B (PB; 50 units), and biotype-specific phages (1). The genetic traits include the variants of the gene encoding the cholera toxin subunit B (ctxB). In addition, the repeat sequence transcriptional regulator (rstR) gene and the major toxin coregulated pilus gene (tcpA) possess classical and El Tor-specific alleles, while the repeat in the toxin gene (rtxC) is present in El Tor but absent in classical biotype isolates (4).Several atypical or variant El Tor biotypes have recently been identified. The Matlab variant was the first atypical El Tor biotype. It was identified in Matlab, Bangladesh, between 1991 and 1994 (5). Another study (6) reported a hybrid CTX⌽ isolate carrying El Tor rstR and classical ctxB that has completely replaced the El Tor biotype in Kolkata, India, since 1995. Other atypical El Tor isolates have been reported in other countries in Asia (7,8) and Africa (9, 10), as well as in Mexico (11). Previously, we identified three novel El Tor variants from China in which the ctxB genotype was different from known genotypes (12). These results suggested that there were variants in China; however, the traits have not been investigated.In this study, 330 V. cholerae O1 El Tor biotype isolates were characterized and compared; these isolates were collected over nearly 50 years (1961 to 2010) and were obtained from different provinces in China from 1961to 2010, either from outbreaks or sporadic cases. All of the bacterial isolates were screened for the oxidase reaction and were identified by a slide agglutination test using specific polyvalent antisera against V. cholerae O1 (Ogawa and Inaba; S&A Reagents Lab, Bangkok, Thailand). The serogroups of these isolates were reconfirmed by real-time PCR targeting the O1 rfb-specific O biosynthetic gene (13).For phenotypic tests, polymyxin B (PB; 50 units) susceptibility test, CCA, and the VP reaction were performed using standard procedures (14) and a previous report (15). The V. cholerae reference classical isolate 569B and the reference El Tor isolate N16961 were included as controls. The phenotypic tests were repeated three times to ensure reliable results.To complement the phenotypic characterization of th...

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Novel ctxB variants of Vibrio cholerae O1 isolates, China

Cited by 17 publications

References 31 publications

Distribution of Virulence-Associated Genes and Genetic Relationships in Non-O1/O139 Vibrio cholerae Aquatic Isolates from China

Distribution of Virulence-Associated Genes and Genetic Relationships in Non-O1/O139 Vibrio cholerae Aquatic Isolates from China

A Molecular Surveillance Reveals the Prevalence of Vibrio cholerae O139 Isolates in China from 1993 to 2012

The Seventh Pandemic Vibrio cholerae O1 El Tor Isolate in China Has Undergone Genetic Shifts

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