Phenotypic and genetic characterization of Vibrio cholerae O1 clinical isolates collected through national antimicrobial resistance surveillance network in Nepal

Shakya, Geeta; Kim, Dong Wook; Clemens, John D.; Malla, Sarala; Upadhyaya, Bishnu Prasad; Dumre, Shyam Prakash; Shrestha, Sirjana; Adhikari, Shailaja; Sharma, Supriya; Rijal, Nisha; Shrestha, Sanjaya; Mason, Carl J.; Kansakar, Palpasa

doi:10.1007/s11274-012-1077-3

Cited by 10 publications

(9 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The catastrophic cholera outbreak in Haiti in 2010 was caused by a Wave 3 strain that contained ctxB genotype 7 [10], [14], [15]. We noted the CTX phage of Haitian strains differed from CTX-3b by several SNPs.…”

Section: Introductionmentioning

confidence: 80%

Molecular Insights Into the Evolutionary Pathway of Vibrio cholerae O1 Atypical El Tor Variants

et al. 2014

Self Cite

View full text Add to dashboard Cite

Pandemic V. cholerae strains in the O1 serogroup have 2 biotypes: classical and El Tor. The classical biotype strains of the sixth pandemic, which encode the classical type cholera toxin (CT), have been replaced by El Tor biotype strains of the seventh pandemic. The prototype El Tor strains that produce biotype-specific cholera toxin are being replaced by atypical El Tor variants that harbor classical cholera toxin. Atypical El Tor strains are categorized into 2 groups, Wave 2 and Wave 3 strains, based on genomic variations and the CTX phage that they harbor. Whole-genome analysis of V. cholerae strains in the seventh cholera pandemic has demonstrated gradual changes in the genome of prototype and atypical El Tor strains, indicating that atypical strains arose from the prototype strains by replacing the CTX phages. We examined the molecular mechanisms that effected the emergence of El Tor strains with classical cholera toxin-carrying phage. We isolated an intermediary V. cholerae strain that carried two different CTX phages that encode El Tor and classical cholera toxin, respectively. We show here that the intermediary strain can be converted into various Wave 2 strains and can act as the source of the novel mosaic CTX phages. These results imply that the Wave 2 and Wave 3 strains may have been generated from such intermediary strains in nature. Prototype El Tor strains can become Wave 3 strains by excision of CTX-1 and re-equipping with the new CTX phages. Our data suggest that inter-chromosomal recombination between 2 types of CTX phages is possible when a host bacterial cell is infected by multiple CTX phages. Our study also provides molecular insights into population changes in V. cholerae in the absence of significant changes to the genome but by replacement of the CTX prophage that they harbor.

show abstract

Section: Introductionmentioning

confidence: 80%

Molecular Insights Into the Evolutionary Pathway of Vibrio cholerae O1 Atypical El Tor Variants

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…In Nepal, at least three different resistance phenotypes of V. cholerae were previously reported to be in circulation [24]. A recent study reported temporal variation in drug resistance patterns of V. cholerae associated with cholera in Nepal between 2007 and 2010 [25]. In the present study, V. cholerae O1 associated with diarrheal outbreaks in Nepal, including those isolated from natural surface water samples, were MDR showing resistance towards SXT, NA, and S, suggesting that drug resistance patterns can change temporally, and spatially, and thus require continuous monitoring in order to select an effective drug of choice at any given time.…”

Section: Discussionmentioning

confidence: 99%

“…Genotypes 1, 2, 3, 7, 10, and 11 were found in serogroup O1 strains, genotypes 3, 4, 5, and 6 were found in serogroup O139 strains, and genotypes 8 and 9 were found only in serogroups O27 and O37 [46]. A previous study showed the presence of two different ctxB genotypes, namely 1 and 7, among V. cholerae associated with cholera in Nepal between 2007 and 2010 [25]. In the present study, ctxB genotype 7 was confirmed for all 28 V. cholerae O1 strains isolated in 2012 from three districts of Nepal.…”

Section: Discussionmentioning

confidence: 99%

“…A recent MLVA-based study carried out with V. cholerae O1 strains associated with cholera between 2007 and 2010 showed the circulation of four different groups of altered V. cholerae O1 El Tor strains in Western Nepal including Butwal and Kathmandu [25]. The molecular basis and epidemiological significance of such genetically divergent V. cholerae O1 altered El Tor remains an interesting area to explore.…”

Section: Discussionmentioning

confidence: 99%

“…Cholera treatment is often hindered due to emergence of multi-drug resistance in V. cholerae [20,21]. Compounding the problem related to selecting an effective antibiotic for cholera treatments, even less is known about drug resistance properties of V. cholerae O1 bacterium in Nepal [22-25]. In the present study, V. cholerae strains associated with the 2012 cholera outbreaks in three district of Nepal were investigated for microbiological and molecular characteristics.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cholera outbreaks (2012) in three districts of Nepal reveal clonal transmission of multi-drug resistant Vibrio choleraeO1

et al. 2014

View full text Add to dashboard Cite

BackgroundAlthough endemic cholera causes significant morbidity and mortality each year in Nepal, lack of information about the causal bacterium often hinders cholera intervention and prevention. In 2012, diarrheal outbreaks affected three districts of Nepal with confirmed cases of mortality. This study was designed to understand the drug response patterns, source, and transmission of Vibrio cholerae associated with 2012 cholera outbreaks in Nepal.MethodsV. cholerae (n = 28) isolated from 2012 diarrhea outbreaks {n = 22; Kathmandu (n = 12), Doti (n = 9), Bajhang (n = 1)}, and surface water (n = 6; Kathmandu) were tested for antimicrobial response. Virulence properties and DNA fingerprinting of the strains were determined by multi-locus genetic screening employing polymerase chain reaction, DNA sequencing, and pulsed-field gel electrophoresis (PFGE).ResultsAll V. cholerae strains isolated from patients and surface water were confirmed to be toxigenic, belonging to serogroup O1, Ogawa serotype, biotype El Tor, and possessed classical biotype cholera toxin (CTX). Double-mismatch amplification mutation assay (DMAMA)-PCR revealed the V. cholerae strains to possess the B-7 allele of ctx subunit B. DNA sequencing of tcpA revealed a point mutation at amino acid position 64 (N → S) while the ctxAB promoter revealed four copies of the tandem heptamer repeat sequence 5'-TTTTGAT-3'. V. cholerae possessed all the ORFs of the Vibrio seventh pandemic island (VSP)-I but lacked the ORFs 498–511 of VSP-II. All strains were multidrug resistant with resistance to trimethoprim-sulfamethoxazole (SXT), nalidixic acid (NA), and streptomycin (S); all carried the SXT genetic element. DNA sequencing and deduced amino acid sequence of gyrA and parC of the NAR strains (n = 4) revealed point mutations at amino acid positions 83 (S → I), and 85 (S → L), respectively. Similar PFGE (NotI) pattern revealed the Nepalese V. cholerae to be clonal, and related closely with V. cholerae associated with cholera in Bangladesh and Haiti.ConclusionsIn 2012, diarrhea outbreaks in three districts of Nepal were due to transmission of multidrug resistant V. cholerae El Tor possessing cholera toxin (ctx) B-7 allele, which is clonal and related closely with V. cholerae associated with cholera in Bangladesh and Haiti.

show abstract

Genomic Science in Understanding Cholera Outbreaks and Evolution of Vibrio cholerae as a Human Pathogen

Robins

Mekalanos

2014

Cholera Outbreaks

View full text Add to dashboard Cite

Modern genomic and bioinformatic approaches have been applied to interrogate the V. cholerae genome, the role of genomic elements in cholera disease, and the origin, relatedness, and dissemination of epidemic strains. A universal attribute of choleragenic strains includes a repertoire of pathogenicity islands and virulence genes, namely the CTX–ϕ prophage and Toxin Co-regulated Pilus (TCP) in addition to other virulent genetic elements including those referred to as Seventh Pandemic Islands. During the last decade, the advent of Next Generation Sequencing (NGS) has provided highly resolved and often complete genomic sequences of epidemic isolates in addition to both clinical and environmental strains isolated from geographically unconnected regions. Genomic comparisons of these strains, as was completed during and following the Haitian outbreak in 2010, reveals that most epidemic strains appear closely related, regardless of region of origin. Non-O1 clinical or environmental strains may also possess some virulence islands, but phylogenic analysis of the core genome suggests they are more diverse and distantly related than those isolated during epidemics. Like Haiti, genomic studies that examine both the Vibrio core- and pan-genome in addition to Single Nucleotide Polymorphisms (SNPs) conclude that a number of epidemics are caused by strains that closely resemble those in Asia, and often appear to originate there and then spread globally. The accumulation of SNPs in the epidemic strains over time can then be applied to better understand the evolution of the V. cholerae genome as an etiological agent.

show abstract

Phenotypic and genetic characterization of Vibrio cholerae O1 clinical isolates collected through national antimicrobial resistance surveillance network in Nepal

Cited by 10 publications

References 26 publications

Molecular Insights Into the Evolutionary Pathway of Vibrio cholerae O1 Atypical El Tor Variants

Molecular Insights Into the Evolutionary Pathway of Vibrio cholerae O1 Atypical El Tor Variants

Cholera outbreaks (2012) in three districts of Nepal reveal clonal transmission of multi-drug resistant Vibrio choleraeO1

Genomic Science in Understanding Cholera Outbreaks and Evolution of Vibrio cholerae as a Human Pathogen

Contact Info

Product

Resources

About