Corrigendum: Surveillance and Genomics of Toxigenic Vibrio cholerae O1 From Fish, Phytoplankton and Water in Lake Victoria, Tanzania.
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SUBMITTER: Hounmanou YMG
PROVIDER: S-EPMC6934033 | biostudies-literature | 2019
REPOSITORIES: biostudies-literature
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Corrigendum: Surveillance and Genomics of Toxigenic <i>Vibrio cholerae</i> O1 From Fish, Phytoplankton and Water in Lake Victoria, Tanzania.
Hounmanou Yaovi M Gildas YMG Leekitcharoenphon Pimlapas P Hendriksen Rene S RS Dougnon Tamegnon V TV Mdegela Robinson H RH Olsen John E JE Dalsgaard Anders A
Frontiers in microbiology 20191220
[This corrects the article DOI: 10.3389/fmicb.2019.00901.]. ...[more]
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Project description:The occurrence of toxigenic Vibrio cholerae O1 during a non- outbreak period in Lake Victoria was studied and genetic characteristics for environmental persistence and relatedness to pandemic strains were assessed. We analyzed 360 samples of carps, phytoplankton and water collected in 2017 during dry and rainy seasons in the Tanzanian basin of Lake Victoria. Samples were tested using PCR (ompW and ctxA) with DNA extracted from bacterial isolates and samples enriched in alkaline peptone water. Isolates were screened with polyvalent antiserum O1 followed by antimicrobial susceptibility testing. Whole genome sequencing and bioinformatics tools were employed to investigate the genomic characteristics of the isolates. More V. cholerae positive samples were recovered by PCR when DNA was obtained from enriched samples than from isolates (69.0% vs. 21.3%, p < 0.05), irrespectively of season. We identified ten V. cholerae O1 among 22 ctxA-positive isolates. Further studies are needed to serotype the remaining ctxA-positive non-O1 strains. Sequenced strains belonged to El Tor atypical biotype of V. cholerae O1 of MLST ST69 harboring the seventh pandemic gene. Major virulence genes, ctxA, ctxB, zot, ace, tcpA, hlyA, rtxA, ompU, toxR, T6SS, alsD, makA and pathogenicity islands VPI-1, VPI-2, VSP-1, and VSP-2 were found in all strains. The strains contained Vibrio polysaccharide biosynthesis enzymes, the mshA gene and two-component response regulator proteins involved in stress response and autoinducers for quorum sensing and biofilm formation. They carried the SXT integrative conjugative element with phenotypic and genotypic resistance to aminoglycoside, sulfamethoxazole, trimethoprim, phenicol, and quinolones. Strains contained a multidrug efflux pump component and were resistant to toxic compounds with copper homeostasis and cobalt-zinc-cadmium resistance proteins. The environmental strains belonged to the third wave of the seventh pandemic and most are genetically closely related to recent outbreak strains from Tanzania, Kenya, and Uganda with as low as three SNPs difference. Some strains have persisted longer in the environment and were more related to older outbreak strains in the region. V. cholerae O1 of outbreak potential seem to persist in Lake Victoria through interactions with fish and phytoplankton supported by the optimum water parameters and intrinsic genetic features enhancing survival in the aquatic environment.
| S-EPMC6503148 | biostudies-literature
Project description:Pathogenic strains of Vibrio cholerae are responsible for endemic and pandemic outbreaks of the disease cholera. The complete toxigenic mechanisms underlying virulence in Vibrio strains are poorly understood. The hypothesis of this work was that virulent versus non-virulent strains of V. cholerae harbor distinctive genomic elements that encode virulence. The purpose of this study was to elucidate genomic differences between the O1 serotypes and non-O1 V. cholerae PS15, a non-toxigenic strain, in order to identify novel genes potentially responsible for virulence. In this study, we compared the whole genome of the non-O1 PS15 strain to the whole genomes of toxigenic serotypes at the phylogenetic level, and found that the PS15 genome was distantly related to those of toxigenic V. cholerae. Thus we focused on a detailed gene comparison between PS15 and the distantly related O1 V. cholerae N16961. Based on sequence alignment we tentatively assigned chromosome numbers 1 and 2 to elements within the genome of non-O1 V. cholerae PS15. Further, we found that PS15 and O1 V. cholerae N16961 shared 98% identity and 766 genes, but of the genes present in N16961 that were missing in the non-O1 V. cholerae PS15 genome, 56 were predicted to encode not only for virulence-related genes (colonization, antimicrobial resistance, and regulation of persister cells) but also genes involved in the metabolic biosynthesis of lipids, nucleosides and sulfur compounds. Additionally, we found 113 genes unique to PS15 that were predicted to encode other properties related to virulence, disease, defense, membrane transport, and DNA metabolism. Here, we identified distinctive and novel genomic elements between O1 and non-O1 V. cholerae genomes as potential virulence factors and, thus, targets for future therapeutics. Modulation of such novel targets may eventually enhance eradication efforts of endemic and pandemic disease cholera in afflicted nations.
| S-EPMC4338557 | biostudies-literature
Project description:Since the identification of the first cholera case in 2010, the disease has spread in epidemic form throughout the island nation of Haiti; as of 2014, about 700,000 cholera cases have been reported, with over 8,000 deaths. While case numbers have declined, the more fundamental question of whether the causative bacterium, Vibrio cholerae has established an environmental reservoir in the surface waters of Haiti remains to be elucidated. In a previous study conducted between April 2012 and March 2013, we reported the isolation of toxigenic V. cholerae O1 from surface waters in the Ouest Department. After a second year of surveillance (April 2013 to March 2014) using identical methodology, we observed a more than five-fold increase in the number of water samples containing culturable V. cholerae O1 compared to the previous year (1.7% vs 8.6%), with double the number of sites having at least one positive sample (58% vs 20%). Both seasonal water temperatures and precipitation were significantly related to the frequency of isolation. Our data suggest that toxigenic V. cholerae O1 are becoming more common in surface waters in Haiti; while the basis for this increase is uncertain, our findings raise concerns that environmental reservoirs are being established.
| S-EPMC4390201 | biostudies-literature
Project description:Prevalence of toxigenic Vibrio cholerae O1 in aquatic reservoirs in Bangladesh apparently increases coinciding with the occurrence of seasonal cholera epidemics. In between epidemics, these bacteria persist in water mostly as dormant cells, known as viable but non-culturable cells (VBNC), or conditionally viable environmental cells (CVEC), that fail to grow in routine culture. CVEC resuscitate to active cells when enriched in culture medium supplemented with quorum sensing autoinducers CAI-1 or AI-2 which are signal molecules that regulate gene expression dependent on cell density. V. cholerae O1 mutant strains with inactivated cqsS gene encoding the CAI-1 receptor has been shown to overproduce AI-2 that enhance CVEC resuscitation in water samples. Since V. cholerae non-O1 non-O139 (non-cholera-vibrios) are abundant in aquatic ecosystems, we identified and characterized naturally occurring variant strains of V. cholerae non-O1 non-O139 which overproduce AI-2, and monitored their co-occurrence with V. cholerae O1 in water samples. The nucleotide sequence and predicted protein products of the cqsS gene carried by AI-2 overproducing variant strains showed divergence from that of typical V. cholerae O1 or non-O1 strains, and their culture supernatants enhanced resuscitation of CVEC in water samples. Furthermore, prevalence of V. cholerae O1 in the aquatic environment was found to coincide with an increase in AI-2 overproducing non-O1 non-O139 strains. These results suggest a possible role of non-cholera vibrios in the environmental biology of the cholera pathogen, in which non-O1 non-O139 variant strains overproducing AI-2 presumably contribute in resuscitation of the latent pathogen, leading to seasonal cholera epidemics. Importance. Toxigenic Vibrio cholerae which causes seasonal epidemics of cholera persists in aquatic reservoirs in endemic areas. The bacteria mostly exist in a dormant state during inter-epidemic periods, but periodically resuscitate to the active form. The resuscitation is enhanced by signal molecules called autoinducers (AIs). Toxigenic V. cholerae can be recovered from water samples that normally test negative for the organism in conventional culture, by supplementing the culture medium with exogenous AIs. V. cholerae belonging to the non-O1 non-O139 serogroups which do not cause cholera are also abundant in natural waters, and they are capable of producing AIs. In this study we characterized V. cholerae non-O1 non-O139 variant strains which overproduce an autoinducer called AI-2, and found that the abundance of the cholera pathogen in aquatic reservoirs correlates with an increase in the AI-2 overproducing strains. Our results suggest a probable role of these variant strains in the environmental biology and epidemiology of toxigenic V. cholerae, and may lead to novel means for surveillance, prevention and control of cholera.
| S-EPMC8253391 | biostudies-literature
Project description:This study was carried out in order to investigate the spatial variation of algal toxin (microcystin) concentrations along the shoreline of Lake Victoria. A total of 16 nearshore stations differing in connectivity to the main lake basin were categorized as either closed bays (ratio of bay area to bay opening < 1) or open bays (ratio ? 1) and sampled during November and December 2009. Water samples were analyzed for total phosphorus (TP), chlorophyll a, phytoplankton community composition and concentrations of microcystin (MC). Open and closed bays were significantly different for phytoplankton abundance and composition: Average phytoplankton biovolume was higher for closed bays (45 mm3 L-1 ± 11 SE) than open bays (5 ± 2 mm3 L-1). Cyanobacterial biovolume (mainly Microcystis spp., Anabaena spp. and Planktolyngbya spp.) also was significantly higher in closed bays (82 ± 9% of total biovolume) than in open bays (44 ± 5%). In contrast, diatom biovolume was lower in closed bays (7 ± 1%) than in open bays (36 ± 6%). MCs were found only among sites from closed bays and concentrations ranged from 0.4 to 13 ?g L-1 MC-LR equiv. and coincided with high abundance of Microcystis spp. It is concluded that the level of water exchange from individual bays to the main basin is an important factor influencing eutrophication and microcystin production in nearshore habitats of Lake Victoria.
| S-EPMC5221727 | biostudies-literature
Project description:BackgroundToxigenic Vibrio cholerae serogroup O1 is the causative pathogen in the sixth and seventh cholera pandemics. Cholera toxin is the major virulent factor but other virulence and virulence-related factors play certain roles in the pathogenesis and survival in the host. Along with the evolution of the epidemic strains, the virulence-related genes also experience variation, gain and loss, and lead to genetic divergence in different strains.ResultsIn this study, we analyzed the virulence-related gene profiles in the toxigenic serogroup O1 strains isolated from 1923 to 2015, the genomes of which were publicly available. The virulence-related genes of the V. cholerae O1 strains were annotated based on the Virulence Factors Database (VFDB). An average of 230.1 virulence-related genes per strain were identified; significant differences in the average numbers were found between the classical and El Tor biotypes, and increasing trends in the number of virulence-related genes along with the isolation years were observed in the El Tor biotype strains. A total of 176 homologs of virulence-related genes were found from these strains, of which 25 belonged to the core genes, suggesting their conservative and necessary roles in V. cholerae pathogenesis. We described the diversities of the homologs by defining gene sequence type, and illustrated its association with gene duplication; we found that gene duplication clearly increased the complexity of the gene sequence types in the core virulence-related genes. In addition, we provided virulence-related gene profiles whose genetic characteristic depend on the isolation years from the view of gene gain and loss, variation, gene duplication and gene sequence type number.ConclusionsOur study reveals the comprehensive variation dynamics of the virulence-related genes in toxigenic V. cholerae serogroup O1 during epidemics. The increasing trend for the virulence-related genes may suggest the evolutional advantage of strains by gaining virulence-related genes with diverse functional categories.
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Project description:Vibrio cholerae O1 exists as two major serotypes, Inaba and Ogawa, which are associated with the O antigen of the lipopolysaccharide and are capable of unequal reciprocal interconversion. The 20-kilobase rfb regions encoding O-antigen biosynthesis in strains 569B (Inaba) and O17 (Ogawa) have been cloned in Escherichia coli K-12 and the nucleotide sequences have been determined. Besides several base substitutions and a small deletion in the 569B sequence relative to O17, there is a single nucleotide change resulting in a TGA stop codon within the gene for the 32-kDa RfbT protein. We have demonstrated that rfbT is responsible for serotype conversion (Inaba to Ogawa). The construction of a specific rfbT mutation in the Ogawa strain O17, and the ability of the gene from O17 to complement Inaba strains to Ogawa, confirmed rfbT as the gene required for the Ogawa serotype. By Southern hybridization and sequencing of PCR products of a number of strains, we have shown that the changes observed in one Inaba strain (569B) are not conserved in other Inaba strains. This may explain why some Inaba strains are able to convert to Ogawa whereas others are not. The protein encoded by rfbT has been identified and expressed in E. coli K-12 using a phage T7 expression system. Amino-terminal analysis of partially purified protein has identified the translational start of the protein. Primer extension studies have enabled the 5' end of the mRNA to be defined. It exists as a separate transcript from the rest of the rfb region, and the distinctive G + C content of rfbT suggests that it has been acquired from a non-Vibrio source.
| S-EPMC48702 | biostudies-other
Project description:BackgroundCholera has been endemic in Douala, since 1971 when it was first recorded in Cameroon. Outbreaks have often started in slum areas of the city including New Bell. Despite the devastating nature of outbreaks, always resulting in high mortality and morbidity, a paucity of information exists on the reservoirs of the causative agent, V. cholerae, and factors maintaining its persistence. This has complicated disease prevention, resulting in frequent outbreaks of cholera. We investigated water sources in New Bell for contamination with V. cholerae O1 with pathogenic potential, to highlight their role in disease transmission. Antibiotic susceptibility pattern of isolates and the environmental factors maintaining its persistence were investigated.MethodWater samples from various sources (taps, dug wells, streams) were analyzed for contamination with V. cholerae O1 using standard methods. Antibiotic susceptibility was determined by disc diffusion method. Pathogenic potential of isolates was determined by analyzing for genes for cholera toxin (ctx), toxin co-regulated pilus (tcpA), and zonula occludens toxin (zot) by PCR. Physico-chemical characteristics of water (pH, temperature and salinity) were investigated using standard methods. The Spearman's Rank correlation was used to analyze the relationship between physico-chemical factors and the occurrence of V. cholerae O1. Differences were considered significant at P?0.05.ResultsTwenty-five V. cholerae O1 strains were isolated from stream and well samples in both dry and rainy seasons. Twenty-three (92%) isolates were multidrug resistant. All isolates had genes for at least one virulence factor. Cholera toxin gene was detected in 7 isolates. Of the 15 isolates positive for tcpA gene, two had Classical type tcpA while 13 had tcpA El Tor. All tcpA Classical positive isolates were positive for ctx gene. Isolates were grouped into nine genotypes based on the genes analyzed. pH and salinity significantly correlated with isolation of V. cholerae O1.ConclusionMultidrug resistant Vibrio cholerae O1 with pathogenic potential is present in some wells and streams in study area. pH and salinity are among the factors maintaining the persistence of the organism. Findings indicate an urgent need for potable water supply in study area and in addition, regular disinfection of water from contaminated sources to prevent outbreak of cholera.
| S-EPMC3750389 | biostudies-literature
Project description:Vibrio cholerae is ubiquitous in aquatic environments, with environmental toxigenic V. cholerae O1 strains serving as a source for recurrent cholera epidemics and pandemic disease. However, a number of questions remain about long-term survival and evolution of V. cholerae strains within these aquatic environmental reservoirs. Through monitoring of the Haitian aquatic environment following the 2010 cholera epidemic, we isolated two novel non-toxigenic (ctxA/B-negative) Vibrio cholerae O1. These two isolates underwent whole-genome sequencing and were investigated through comparative genomics and Bayesian coalescent analysis. These isolates cluster in the evolutionary tree with strains responsible for clinical cholera, possessing genomic components of 6th and 7th pandemic lineages, and diverge from "modern" cholera strains around 1548 C.E. [95% HPD: 1532-1555]. Vibrio Pathogenicity Island (VPI)-1 was present; however, SXT/R391-family ICE and VPI-2 were absent. Rugose phenotype conversion and vibriophage resistance evidenced adaption for persistence in aquatic environments. The identification of V. cholerae O1 strains in the Haitian environment, which predate the first reported cholera pandemic in 1817, broadens our understanding of the history of pandemics. It also raises the possibility that these and similar environmental strains could acquire virulence genes from the 2010 Haitian epidemic clone, including the cholera toxin producing CTXϕ.
| S-EPMC5081557 | biostudies-literature
Project description:Cholera outbreaks have occurred in Tanzania since 1974. To date, the genetic epidemiology of these outbreaks has not been assessed.96 Vibrio cholerae O1 isolates from five regions were characterized, and their genetic relatedness assessed using multi-locus variable-number tandem-repeat analysis (MLVA) and whole genome sequencing (WGS).Of the 48 MLVA genotypes observed, 3 were genetically unrelated to any others, while the remaining 45 genotypes separated into three MLVA clonal complexes (CCs) - each comprised of genotypes differing by a single allelic change. In Kigoma, two separate outbreaks, 4 months apart (January and May, 2015), were each caused by genetically distinct strains by MLVA and WGS. Remarkably, one MLVA CC contained isolates from both the May outbreak and ones from the 2011/2012 outbreak in Dar-es-Salaam. However, WGS revealed the isolates from the two outbreaks to be distinct clades. The outbreak that started in August 2015 in Dar-es-Salaam and spread to Morogoro, Singida and Mara was comprised of a single MLVA CC and WGS clade. Isolates from within an outbreak were closely related differing at fewer than 5 nucleotides. All isolates were part of the 3rd wave of the 7th pandemic and were found in four clades related to isolates from Kenya and Asia.We conclude that genetically related V. cholerae cluster in outbreaks, and distinct strains circulate simultaneously.
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