Diversity in the arrangement of the CTX prophages in classical strains of Vibrio cholerae O1

Basu, Arnab

doi:10.1016/s0378-1097(99)00562-5

Cited by 5 publications

(5 citation statements)

References 18 publications

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“…This region originated from prophage islands and is known to exist in two or more copies in pathogenic O1 strains (3,19,53,74). This could explain the presence of two amplification products (alleles) in the V. cholerae O1 In-124(ϩ) strain.…”

Section: Discussionmentioning

confidence: 99%

Vibrio cholerae Strain Typing and Phylogeny Study Based on Simple Sequence Repeats

et al. 2007

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Vibrio cholerae is the etiological agent of cholera. Its natural reservoir is the aquatic environment. To date, practical typing of V. cholerae is mainly serological and requires about 200 antisera. Simple sequence repeats (SSR), also termed VNTR (for variable number of tandem repeats), provide a source of high genomic polymorphism used in bacterial typing. Here we describe an SSR-based typing method that combines the variation in highly mutable SSR loci, with that of shorter, relatively more stable mononucleotide repeat (MNR) loci, for accurate and rapid typing of V. cholerae. Vibrio cholerae, a gram-negative bacterium, is the causal agent of the severe diarrheal disease cholera. Its natural reservoir is the aquatic environment (49, 84). Cholera pandemics are caused by specific serogroups of V. cholerae that are pathogenic only to humans (35,84). Since 1817, V. cholerae has caused a number of pandemics. The first seven were presumed to be caused by O1 serogroup of V. cholerae (68). In October 1992, a new serogroup, defined O139, caused a severe outbreak of cholera in southeast India. Within 10 months, the O139 serogroup was disseminated all over the Indian subcontinent and soon thereafter spread to 11 neighboring countries, temporarily displacing the O1 serogroups (64). Since then both serogroups coexist and are responsible for large outbreaks. Genomic studies indicated that O139 epidemic strain arose by horizontal acquisition of unique DNA (15, 47).Traditionally, V. cholerae classification is serological and requires about 200 antisera based on the somatic O antigen (72). Isolates of V. cholerae are divided into three major subgroups: O1, O139, and non-O1/non-O139, of which only the O1 and O139 serogroups are associated with cholera pandemics and epidemics. Non-O1, non-O139 serogroups are recognized as causative agents of sporadic and localized outbreaks (73). Pathogenic V. cholerae isolates carry virulence genes, such as the toxins genes ctxAB (25,65,68). The environmental V. cholerae strains from non-O1, non-O139 serogroups are a possible natural reservoir of potentially new emerging epidemic strains (67,73). This assumption is supported by the finding that some of these environmental strains harbor virulence genes (23) and thus are likely to evolve into novel pathogenic strains by horizontal gene transfer (24,25). The emergence of new pathogenic V. cholerae strains requires not only an efficient, rapid, and accurate identification tool but also a means for determining genetic relationships among environmental and clinical isolates.Genome-based bacterial identification and typing is essential for several disciplines, including taxonomy, epidemiology, determining phylogenetic relationships, and the study of evolutionary mechanisms. It allows distinguishing among strains within a species to monitor epidemics and routes of contamination. Recent advances in biotechnology have resulted in the development of numerous methods for microorganism typing that differ in their sensitivity, rapidity, complexity, discrimin...

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Section: Discussionmentioning

confidence: 99%

Vibrio cholerae Strain Typing and Phylogeny Study Based on Simple Sequence Repeats

et al. 2007

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“…Traditional culturing methods require time-consuming enrichments and labor-intensive procedures that require several days. However, the TaqMan PCR developed in this study requires only 3 h. Other molecular systems for identifying V. cholerae in food and water, such as PCR fingerprinting and ribotyping (1,41) and detection of virulence genes by PCR ( 6,8,28,36,44,46; Arya, Letter), require additional verification steps that increase analysis time. The real value of the TaqMan PCR is the potential for rapid analysis of numerous pathogen-free samples, thereby allowing laboratories the ability to quickly screen products before they are released for human consumption.…”

Section: Discussionmentioning

confidence: 99%

TaqMan PCR for Detection of Vibrio cholerae O1, O139, Non-O1, and Non-O139 in Pure Cultures, Raw Oysters, and Synthetic Seawater

Lyon

2001

Appl Environ Microbiol

117

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Vibrio cholerae is recognized as a leading human waterborne pathogen. Traditional diagnostic testing for Vibrio is not always reliable, because this bacterium can enter a viable but nonculturable state. Therefore, nucleic acid-based tests have emerged as a useful alternative to traditional enrichment testing. In this article, a TaqMan PCR assay is presented for quantitative detection of V. cholerae in pure cultures, oysters, and synthetic seawater. Primers and probe were designed from the nonclassical hemolysin (hlyA) sequence of V. cholerae strains. This probe was applied to DNA from 60 bacterial strains comprising 21 genera. The TaqMan PCR assay was positive for all of the strains of V. cholerae tested and negative for all other species of Vibrio tested. In addition, none of the other genera tested was amplified with the TaqMan primers and probe used in this study. The results of the TaqMan PCR with raw oysters and spiked with V. cholerae serotypes O1 and O139 were comparable to those of pure cultures. The sensitivity of the assay was in the range of 6 to 8 CFU g ؊1 and 10 CFU ml ؊1 in spiked raw oyster and synthetic seawater samples, respectively. The total assay could be completed in 3 h. Quantification of the Vibrio cells was linear over at least 6 log units. The TaqMan probe and primer set developed in this study can be used as a rapid screening tool for the presence of V. cholerae in oysters and seawater without prior isolation and characterization of the bacteria by traditional microbiological methods.Vibrio cholerae is a waterborne pathogen that causes gastrointestinal disorders with a wide range of clinical manifestations, including vomiting and rice-like diarrhea (24). The association of human illness with consumption of V. choleraecontaminated oysters, seawater, and other shellfish is well documented (29, 37). Consumption of raw oysters correlates strongly with gastrointestinal infections, and several Vibrio species, including strains of Vibrio parahaemolyticus, Vibrio vulnificus, and V. cholerae, have been implicated as the causative agents.Coastal areas with brackish waters and estuarine regions are niches for many Vibrio species, including strains of toxigenic O1 V. cholerae. Epidemic cholera strains are endemic in several regions, including the U.S. gulf coast and Australia, and are occasionally involved in illnesses in these regions (24). Because Vibrio species attach to material suspended in water, shellfish and mollusks that are in these environments can be expected to consume Vibrio during feeding (24).Traditional identification methods currently used are time-consuming and laborious, requiring prolonged incubation and selective enrichment to reduce the growth of background flora. Vibrio cells may also enter a viable but not culturable (VBNC) state, caused by nutrient starvation and physical stress. This may explain the failure of traditional culture techniques to isolate this organism from contaminated water and food samples implicated in food-borne outbreaks (10,27,47). Several investigator...

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“…It has been shown previously that the genome of CTXφ contains a 4.5‐kb central core region comprising the ctxAB , zot , ace , orfU and cep genes. A central core with a repetitive sequence (RS) of 2.4 kb, designated RS2, constitutes the CTX genetic element [9,10]. The CTX genetic element can also be flanked by one or more copies of a 2.7‐kb RS, designated RS1.…”

Section: Introductionmentioning

confidence: 99%

Genomic organisation of the CTX element among toxigenic Vibrio cholerae isolates

Bakhshi

Pourshafie

Navabakbar

et al. 2008

Clinical Microbiology and Infection

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The composition and gene arrangement of the CTX genetic element were compared in 36 Vibrio cholerae isolates obtained during 2004-2006 from Iran. Long-PCR amplification of the CTX genetic element, using primers targeting ig1 and attB2, revealed three PCR products of c. 6.9, 5.6 and 2.6 kb, respectively. Southern blot hybridisation revealed that 30%, 17% and 53% of the isolates had one, two and three copies of the zot gene, respectively. PCR analysis of internal regions showed that isolates with three copies of the CTX genetic element carried one complete (6.9 kb) and two truncated CTX elements (each of 5.6 kb). In contrast, isolates with one or two copies of CTX carried the complete 6.9-kb CTX element. Pulsed-field gel electrophoresis revealed two pulsotypes among the isolates, with 75% of the isolates belonging to pulsotype 2. The pulsotype 2 isolates had varying CTX genomic arrangements, whereas the pulsotype 1 isolates had a homogeneous CTX arrangement. Thus, variations in the content, arrangement and copy number of the CTX genetic element may occur in isolates belonging to the same clone.

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Diversity in the arrangement of the CTX prophages in classical strains of Vibrio cholerae O1

Cited by 5 publications

References 18 publications

Vibrio cholerae Strain Typing and Phylogeny Study Based on Simple Sequence Repeats

Vibrio cholerae Strain Typing and Phylogeny Study Based on Simple Sequence Repeats

TaqMan PCR for Detection of Vibrio cholerae O1, O139, Non-O1, and Non-O139 in Pure Cultures, Raw Oysters, and Synthetic Seawater

Genomic organisation of the CTX element among toxigenic Vibrio cholerae isolates

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