Direct detection of Vibrio cholerae and ctxA in Peruvian coastal water and plankton by PCR

Stress Responses in Pathogenic Vibrios and Their Role in Host and Environmental Survival

Vibrio is a genus of bacteria commonly found in estuarine, marine, and freshwater environments. Vibrio species have evolved to occupy diverse niches in the aquatic ecosystem, with some having complex lifestyles. About a dozen of the described Vibrio species have been reported to cause human disease, while many other species cause disease in other organisms. Vibrio cholerae causes epidemic cholera, a severe dehydrating diarrheal disease associated with the consumption of contaminated food or water. The human pathogenic non-cholera Vibrio species, Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis, septicemia, and other extra-intestinal infections. Infections caused by V. parahaemolyticus and V. vulnificus are normally acquired through exposure to sea water or through consumption of raw or undercooked contaminated seafood. The human pathogenic Vibrios are exposed to numerous different stress-inducing agents and conditions in the aquatic environment and when colonizing a human host. Therefore, they have evolved a variety of mechanisms to survive in the presence of these stressors. Here we discuss what is known about important stress responses in pathogenic Vibrio species and their role in bacterial survival.

Zooplankton act as cruise ships promoting the survival and pathogenicity of pathogenic bacteria

Bacteria in general interact with zooplankton in aquatic ecosystems. These zooplankton-bacterial interactions help to shape the bacterial community by regulating bacterial abundances. Such interactions are even more significant and crucially in need of investigation in the case of pathogenic bacteria, which cause severe diseases in humans and animals. Among the many associations between a host metazoan and pathogenic bacteria, zooplankton provide nutrition and protection from stressful conditions, promote the horizontal transfer of virulence genes, and act as a mode of pathogen transport. These interactions allow the pathogen to survive and proliferate in aquatic environments and to endure water treatment processes, thereby creating a potential risk to human health. This review highlights current knowledge on the contributions of zooplankton to the survival and pathogenicity of pathogenic bacteria. We also discuss the need to consider these interactions as a risk factor in water treatment processes.

Abundance and biofilm formation capability of Vibrio cholerae in aquatic environment with an emphasis on Hilsha fish (Tenualosa ilisha)

The potentially deadly and sporadic diarrhea-causing agent, Vibrio cholerae, is present in a great number in the freshwater aquatic environment and can be transmitted to humans by different aquatic organisms. In the perspective of Bangladesh, an anadromous fish species Hilsha (Tenualosa ilisha) can act as a transmission vehicle of V. cholerae from the aquatic to the household kitchen environment. The present study was carried out to investigate the presence of V. cholerae in the aquatic habitat of Bangladesh with a major emphasis on freshly caught Hilsha fish, along with river water and plankton samples from the fish capture site. The study also detected the biofilm formation capability of V. cholerae within Hilsha fish that might help the transmission and persistence of the pathogen in aquatic habitat. Twenty out of 65 freshly caught fish (30.8%) and 1 out of 15 water samples (6.67%) showed the presence of V. cholerae and none of the plankton samples were positive for V. cholerae. The isolated strains were identified as non-O1 and non-O139 serogroups of V. cholerae and contain some major toxin and virulence genes. A few strains showed cellular cytotoxicity on the HeLa cell line. All strains were able to form biofilm on the microtiter plate and the detection of three genes related to biofilm formation (vpsA, vpsL, and vpsR) were also assayed using qPCR. In this study, the in vitro biofilm formation ability of the isolated strains may indicate the long-term persistence of V. cholerae in different parts of Hilsha fish. The abundance of V. cholerae only in freshly caught Hilsha fish and the absence of the pathogen in the surrounding aquatic environment could stipulate the role of Hilsha fish as one of the major transmission routes of V. cholerae from the freshwater aquatic environment of Bangladesh to the household kitchen environment.

Vibrio pathogenicity island and phage CTX genes in Vibrio alginolyticus isolated from different aquatic environments

In the present study, we investigated the presence of four Vibrio cholerae virulence genes (ctxA, VPI, Zot and ace) in 36 Vibrio alginolyticus isolates obtained from different seawater, sediments and aquatic organisms. We tested the virulence of 13 V. alginolyticus strains against juveniles of Sparus aurata and this virulence was correlated with the presence of V. cholerae virulence genes. A positive amplification for the virulence pathogenicity island was produced by five V. alginolyticus strains and four for cholerae toxin. Some of the V. alginolyticus strains are pathogenic to aquatic animals and might have derived their virulence genes from V. cholerae. V. alginolyticus strains can be considered as a possible reservoir of V. cholerae virulence genes.

Non-serogroup O1/O139 agglutinable Vibrio cholerae: a phylogenetically and genealogically neglected yet emerging potential pathogen of clinical relevance

Somatic antigen agglutinable type-1/139 Vibrio cholerae (SAAT-1/139-Vc) members or O1/O139 V. cholerae have been described by various investigators as pathogenic due to their increasing virulence potential and production of choleragen. Reported cholera outbreak cases around the world have been associated with these choleragenic V. cholerae with high case fatality affecting various human and animals. These virulent Vibrio members have shown genealogical and phylogenetic relationship with the avirulent somatic antigen non-agglutinable strains of 1/139 V. cholerae (SANAS-1/139- Vc) or O1/O139 non-agglutinating V. cholerae (O1/O139-NAG-Vc). Reports on implication of O1/O139-NAGVc members in most sporadic cholera/cholera-like cases of diarrhea, production of cholera toxin and transmission via consumption and/or contact with contaminated water/seafood are currently on the rise. Some reported sporadic cases of cholera outbreaks and observed change in nature has also been tracable to these non-agglutinable Vibrio members (O1/O139-NAGVc) yet there is a sustained paucity of research interest on the non-agglutinable V. cholerae members. The emergence of fulminating extraintestinal and systemic vibriosis is another aspect of SANAS-1/139- Vc implication which has received low attention in terms of research driven interest. This review addresses the need to appraise and continually expand research based studies on the somatic antigen non-serogroup agglutinable type-1/139 V.cholerae members which are currently prevalent in studies of water bodies, fruits/vegetables, foods and terrestrial environment. Our opinion is amassed from interest in integrated surveillance studies, management/control of cholera outbreaks as well as diarrhea and other disease-related cases both in the rural, suburban and urban metropolis.

Recovery of Pasteurization-Resistant Vibrio parahaemolyticus from Seafoods Using a Modified, Two-Step Enrichment

Persistent Vibrio-parahaemolyticus-associated vibriosis cases, attributed, in part, to the inefficient techniques for detecting viable-but-non-culturable (VBNC) Vibrio pathogens and the ingestion of undercooked seafood, is the leading cause of bacterial seafood-borne outbreaks, hospitalizations, and deaths in the United States. The effect of extreme heat processing on Vibrio biology and its potential food safety implication has been underexplored. In the present work, environmental samples from the wet market, lagoon, and estuarine environments were analyzed for V. parahaemolyticus recovery using a modified, temperature-dependent, two-step enrichment method followed by culture-based isolation, phenotype, and genotype characterizations. The work recovered novel strains (30% of 12 isolates) of V. parahaemolyticus from prolonged-heat-processing conditions (80 °C, 20 min), as confirmed by 16S rDNA bacterial identification. Select strains, VHT1 and VHT2, were determined to be hemolysis- and urease-positive pathogens. PCR analyses of chromosomal DNA implicated the tdh-independent, tlh-associated hemolysis in these strains. Both strains exhibited significant, diverse antibiotic profiles (p < 0.05). Turbidimetric and viable count assays revealed the pasteurization-resistant V. parahaemolyticus VHT1/VHT2 (62 °C, 8 h). These findings disclose the efficiency of Vibrio extremist recovery by the modified, two-step enrichment technique and improve knowledge of Vibrio biology essential to food safety reformation.

Vibrio spp.: Life Strategies, Ecology, and Risks in a Changing Environment

Vibrios are ubiquitous bacteria in aquatic systems, especially marine ones, and belong to the Gammaproteobacteria class, the most diverse class of Gram-negative bacteria. The main objective of this review is to update the information regarding the ecology of Vibrio species, and contribute to the discussion of their potential risk in a changing environment. As heterotrophic organisms, Vibrio spp. live freely in aquatic environments, from marine depths to the surface of the water column, and frequently may be associated with micro- and macroalgae, invertebrates, and vertebrates such as fish, or live in symbiosis. Some Vibrio spp. are pathogenic to humans and animals, and there is evidence that infections caused by vibrios are increasing in the world. This rise may be related to global changes in human behavior (increases in tourism, maritime traffic, consumption of seafood, aquaculture production, water demand, pollution), and temperature. Most likely in the future, Vibrio spp. in water and in seafood will be monitored in order to safeguard human and animal health. Regulators of the microbiological quality of water (marine and freshwater) and food for human and animal consumption, professionals involved in marine and freshwater production chains, consumers and users of aquatic resources, and health professionals will be challenged to anticipate and mitigate new risks.

A method for correcting underestimation of enteric pathogen genome quantities in environmental samples

Exposure to enteric pathogens in the environment poses a serious risk for infection and disease. The accurate detection and quantification of enteric pathogens in environmental samples is critical for understanding pathogen transport and fate and developing risk assessment models. In this study, we successfully applied TaqMan real-time PCR assays to quantitatively detect five human-specific pathogens (Shigella/EIEC, Salmonella Typhi, Vibrio cholera, Norovirus, and Giardia) in samples from open drains, canals, floodwater, septic tanks, and anaerobic baffled reactors (ABR) collected in Mirpur, Dhaka, Bangladesh from April to October 2019. Overall, the grab and sediment samples showed low inhibition but the ultrafiltration samples collected from open drain had significantly higher (P = 0.0049) degree of PCR inhibition (median Ct = 31.06) compared to the extraction controls (Ct = 28.54). We developed a two-step method to adjust underestimation of pathogen quantities due to PCR inhibition and non-optimum PCR efficiency. Compared to other sample types, ultrafiltration samples demonstrated a wide range of concentration increase (1.0%-182.5%) by pathogens after adjusting for PCR inhibition and non-optimum efficiencies. These quantitative qPCR assays are successful in quantifying multiple enteric pathogens in environmental samples, and the adjustment method would be useful for correcting underestimates of pathogen quantities due to partial PCR inhibition and non-optimum efficiency.

Identification of chironomid species as natural reservoirs of toxigenic Vibrio cholerae strains with pandemic potential

Vibrio cholerae causes the fatal cholera diarrhea. Chironomids (Diptera; Chironomidae) are abundant in freshwater aquatic habitats and estuaries and are natural reservoirs of V. cholerae. Until now, only the non-O1/O139 serogroups of V. cholerae were identified in chironomids. Here, we explored whether chironomids are natural reservoirs of V. cholerae O1/O139 serogroups, which are associated with cholera endemics and pandemics. All four life stages of chironomids were sampled from two rivers, and a laboratory culture in Pune, India, and from a pond in Israel. In total, we analyzed 223 chironomid samples. The presence of V. cholerae O1/O139 serogroups was verified using molecular tools. Nine chironomid species were identified; of them, Chironomus circumdatus was the most abundant. The presence of V. cholerae serogroup O1 and the cholera toxin genes were detected in samples from all chironomid species. However, serogroup O139 was detected in only two chironomid species. Besides PCR to detect specific genes, a metagenomic analysis that was performed in three selected C. ramosus larvae, identified a list of virulence genes associated with V. cholerae. The findings provide evidence that chironomids are natural reservoirs of toxigenic V. cholerae O1/O139. Chironomid populations and V. cholerae show biannual peak patterns. A similar pattern is found for cholera epidemics in the Bengal Delta region. Thus, we hypothesize that monitoring chironomids in endemic areas of the disease may provide a novel tool for predicting and preventing cholera epidemics. Moreover, serogroup O139 was detected only in two chironomid species that have a restricted distribution in the Indian subcontinent, possibly explaining why the distribution of the O139 serogroup is limited.

Aptamer-nanobody based ELASA for detection of Vibrio cholerae O1

Background and Objectives

In recent years, the prevalence of diseases caused by Vibrio spp. is increasing in the world, and among them species, Vibrio cholerae is the most important Vibrio associated with pandemic and epidemic cholera outbreaks. Therefore, the development of a reliable method for early and accurate detection of V. cholerae for management of diseases is a real need. Aptamers with the ability to detect targets with high specificity and accuracy can be one of the candidates used for the whole cell and thereby V. cholerae detection.

Materials and Methods

In this research high-affinity DNA aptamers against with two major serotypes of Inaba (ATCC 39315) and Ogawa (clinical sample) were selected from DNA aptamer library through 12 rounds of Systematic Evolution of Ligands by Exponential (SELEX) enrichment procedure using live cells as a target which monitored with flow cytometry.

Results

The binding efficiency and dissociation constant of the isolated aptamers V.ch47 and V.ch27 were 56.4%, 53.3% and 15.404 ± 4.776 pM, 20.186 ± 3.655 pM, respectively. A sandwich Enzyme-linked aptamer sorbent assay (ELASA) was developed with the biotinylated V.ch47 aptamer and our previously developed nanobody anti-Lipopolysaccharides (LPS). We optimized this system with V. cholerae O1 and analyzed their cross reactivity with close physiological bacteria. The threshold of detection was obtained 10⁴ CFU/ml in the sandwich ELASA process.

Conclusion

Our results showed that the sandwich ELASA is sensitive enough for the rapid detection of V. cholerae from other bacteria.

Environmental Reservoirs of Vibrio cholerae: Challenges and Opportunities for Ocean-Color Remote Sensing

The World Health Organization has estimated the burden of the on-going pandemic of cholera at 1.3 to 4 million cases per year worldwide in 2016, and a doubling of case-fatality-rate to 1.8% in 2016 from 0.8% in 2015. The disease cholera is caused by the bacterium Vibrio cholerae that can be found in environmental reservoirs, living either in free planktonic form or in association with host organisms, non-living particulate matter or in the sediment, and participating in various biogeochemical cycles. An increasing number of epidemiological studies are using land- and water-based remote-sensing observations for monitoring, surveillance, or risk mapping of Vibrio pathogens and cholera outbreaks. Although the Vibrio pathogens cannot be sensed directly by satellite sensors, remotely-sensed data can be used to infer their presence. Here, we review the use of ocean-color remote-sensing data, in conjunction with information on the ecology of the pathogen, to map its distribution and forecast risk of disease occurrence. Finally, we assess how satellite-based information on cholera may help support the Sustainable Development Goals and targets on Health (Goal 3), Water Quality (Goal 6), Climate (Goal 13), and Life Below Water (Goal 14).

Detection of Cholera Toxin-Producing Vibrio cholerae in Phytoplankton from Santubong and Samariang Estuaries

Many cholera outbreaks worldwide were associated with cholera toxin-producing Vibrio cholerae. The bacteria are ubiquitous in aquatic environment, whilst phytoplankton is associated with adaptation of the Vibrio species. This study was conducted to detect cholera toxin-producing Vibrio cholerae, and to determine association of the selected water physicochemical parameters with the number of the bacteria. In this study, a total of ten phytoplankton samples were collected at Santubong and Samariang Estuaries in Kuching, Sarawak. Water physicochemical parameters (temperature, pH and salinity) were recorded. Vibrio bacteria were cultivated on thiosulfate citrate bile-salts sucrose selective agar and analysed for cholera toxin-producing Vibrio cholerae using polymerase chain reaction by targeting ctxA gene that encodes for virulence cholera enterotoxin subunit A. The result revealed that a range of 1.0 × 107 – 8.0 × 107 CFU/ml of yellow colonies growing on the thiosulfate citrate bile-salts sucrose agars. Inversely, no samples were positive with cholera toxin-producing Vibrio cholerae. The physicochemical parameters at Samariang Estuary were more associated with the number of bacteria in the samples compared to Santubong Estuary.

Possible impacts of sea level rise on disease transmission and potential adaptation strategies, a review

Sea levels are projected to rise in response to climate change, causing the intrusion of sea water into land. In flat coastal regions, this would generate an increase in shallow water covered areas with limited circulation. This scenario raises a concern about the consequences it could have on human health, specifically the possible impacts on disease transmission. In this review paper we identified three categories of diseases which are associated with water and whose transmission can be affected by sea level rise. These categories include: mosquitoborne diseases, naturalized organisms (Vibrio spp. and toxic algae), and fecal-oral diseases. For each disease category, we propose comprehensive adaptation strategies that would help minimize possible health risks. Finally, the City of Key West, Florida is analyzed as a case study, due to its inherent vulnerability to sea level rise. Current and projected adaptation techniques are discussed as well as the integration of additional recommendations, focused on disease transmission control. Given that sea level rise will likely continue into the future, the promotion and implementation of positive adaptation strategies is necessary to ensure community resilience.

Modulating the Global Response Regulator, LuxO of V. cholerae Quorum Sensing System Using a Pyrazine Dicarboxylic Acid Derivative (PDCApy): An Antivirulence Approach

Vibrio cholerae is a Gram-negative pathogen which causes acute diarrhoeal disease, cholera by the expression of virulence genes through quorum sensing (QS) mechanism. The QS circuit of V. cholerae is controlled by the global quorum regulator, LuxO, which at low cell density (LCD) state produces major virulence factors such as, toxin co-regulated pilus (TCP) and cholera toxin (CT) to mediate infection. On the contrary, at the high cell density (HCD) state the virulent genes are downregulated and the vibrios are detached from the host intestinal epithelial cells, promoted by HapA protease. Hence, targeting the global regulator LuxO would be a promising approach to modulate the QS to curtail V. cholerae pathogenesis. In our earlier studies, LuxO targeted ligand, 2,3 pyrazine dicarboxylic acid (PDCA) and its derivatives having desired pharmacophore properties were chemically synthesized and were shown to have biofilm inhibition as well as synergistic activity with the conventionally used antibiotics. In the present study, the QS modulatory effect of the PDCA derivative with pyrrolidine moiety designated as PDCA^py against the V. cholerae virulence gene expression was analyzed at various growth phases. The data significantly showed a several fold reduction in the expression of the genes, tcp and ct whereas the expression of hapR was upregulated at the LCD state. In addition, PDCA^py reduced the adhesion and invasion of the vibrios onto the INT407 intestinal cell lines. Collectively, our data suggest that PDCA^py could be a potential QS modulator (QSM) for the antivirulence therapeutic approach.

Respiratory Problems Associated with Surfing in Coastal Waters

A pilot project was conducted to examine the health status and possible adverse health effects associated with seawater exposure (microbial water-quality indicators and phytoplankton abundance and their toxins) of surfers in Monterey Bay, Central California coastal waters. Forty-eight surfers enrolled in the study and completed an initial health background survey and weekly health surveys online using Survey Monkey. Descriptive statistics and generalized estimating equation, a regression technique, were used to identify longitudinal and correlated results. The surfers were predominately Caucasian, male, and physically active. They surfed approximately 4 h a week. Their average age was 34 years. The data indicated that the surfers were generally "healthy," with a low prevalence of diabetes, high cholesterol, and hypertension. Their most common health problems were allergies and asthma. During the study, 10% of the surfers reported gastrointestinal symptoms and 29% reported upper respiratory symptoms. This study suggests surfers were significantly more likely to report upper respiratory symptoms when they had a history of allergies, housemates with upper respiratory symptoms, and/or a history of previous adverse health symptoms while surfing during a "red tide" (an event often associated with the presence of phytoplankton toxins). Additionally, female surfers reported upper respiratory symptoms more than males.

Ecological fitness and virulence features of Vibrio parahaemolyticus in estuarine environments

Vibrio parahaemolyticus is a commonly encountered and highly successful organism in marine ecosystems. It is a fast-growing, extremely versatile copiotroph that is active over a very broad range of conditions. It frequently occurs suspended in the water column (often attached to particles or zooplankton), and is a proficient colonist of submerged surfaces. This organism is an important pathogen of animals ranging from microcrustaceans to humans and is a causative agent of seafood-associated food poisoning. This review examines specific ecological adaptations of V. parahaemolyticus, including its broad tolerances to temperature and salinity, its utilization of a wide variety of organic carbon and energy sources, and its pervasive colonization of suspended and stationary materials that contribute to its success and ubiquity in temperate and tropical estuarine ecosystems. Several virulence-related features are examined, in particular the thermostable direct hemolysin (TDH), the TDH-related hemolysin (TRH), and the type 3 secretion system, and the possible importance of these features in V. parahaemolyticus pathogenicity is explored. The impact of new and much more effective PCR primers on V. parahaemolyticus detection and our views of virulent strain abundance are also described. It is clear that strains carrying the canonical virulence genes are far more common than previously thought, which opens questions regarding the role of these genes in pathogenesis. It is also clear that virulence is an evolving feature of V. parahaemolyticus and that novel combinations of virulence factors can lead to emergent virulence in which a strain that is markedly more pathogenic evolves and propagates to produce an outbreak. The effects of global climate change on the frequency of epidemic disease, the geographic distribution of outbreaks, and the human impacts of V. parahaemolyticus are increasing and this review provides information on why this ubiquitous human pathogen has increased its footprint and its significance so dramatically.

Detection of Intestinal Pathogens in River, Shore, and Drinking Water in Lima, Peru

Water quality management is an ongoing struggle for many locations worldwide. Current testing of water supplies can be time-consuming, expensive, and lack sensitivity. This study describes an alternative, easy-to-use, and inexpensive method to water sampling and testing at remote locations. This method was employed to detect a number of intestinal pathogens in various locations of Lima, Peru. A total of 34 PCR primer pairs were tested for specificity and high-yield amplification for 12 different pathogens using known DNA templates. Select primers for each pathogen were then tested for minimum detection limits of DNA. Water samples were collected from 22 locations. PCR was used to detect the presence of a pathogen, virulence factors, or differentiate between pathogenic species. In 22 water samples, cholera toxin gene was detected in 4.5% of samples, C. perfringens DNA was detected in 50% of samples, E. histolytica DNA was detected in 54.5% of samples, Giardia intestinalis DNA was detected in 4.5% of samples, Leptospira spp. DNA was detected in 29% of samples, and T. gondii DNA was detected in 31.8% of samples. DNA from three pathogens, C. perfringens, E. histolytica, and T. gondii, were found in residential samples, which accounted for 10 out of 22 samples.

Hybridoma as a specific, sensitive, and ready to use sensing element: a rapid fluorescence assay for detection of Vibrio cholerae O1

Over the last decade, isolation and purification of monoclonal antibodies, for diagnostic analysis, have been carried out using the hybridoma expression system. The present study describes a novel example of a detection system using hybridoma cells containing antibody against O1 antigen directly for V. cholerae diagnosis, which is a major health problem in many parts of the world, especially in developing countries. This method has advantages such as simplicity, ease of process, and it does not require manipulation of hybridoma cell. For this approach, an efficient amount of fluorescence calcium indicator, fura 2-AM, was utilized, which emitted light when the intracellular calcium concentration increased as result of antigen binding to specific antibody. More reliable results are obtained via this method and it is considerably faster than other methods, which has the response time of less than 45 s for detection of V. Cholerae O1. Also, the limit of detection was computed to be 50 CFU/mL (<13 CFU per assay). In addition, no significant responses were observed in the presence of other bacteria with specific hybridoma or other cell lines exposed to V. cholerae O1. Furthermore, this method was successfully applied to V. cholerae O1 detection in spiked environmental samples, including water and stool samples without any pretreatment. All results reveal that hybridoma cells can provide a valuable, simple, and ready to use tool for rapid detection of other pathogenic bacteria, toxins, and analytes.

Response of Vibrio cholerae to Low-Temperature Shifts: CspV Regulation of Type VI Secretion, Biofilm Formation, and Association with Zooplankton

The ability to sense and adapt to temperature fluctuation is critical to the aquatic survival, transmission, and infectivity of Vibrio cholerae, the causative agent of the disease cholera. Little information is available on the physiological changes that occur when V. cholerae experiences temperature shifts. The genome-wide transcriptional profile of V. cholerae upon a shift in human body temperature (37°C) to lower temperatures, 15°C and 25°C, which mimic those found in the aquatic environment, was determined. Differentially expressed genes included those involved in the cold shock response, biofilm formation, type VI secretion, and virulence. Analysis of a mutant lacking the cold shock gene cspV, which was upregulated >50-fold upon a low-temperature shift, revealed that it regulates genes involved in biofilm formation and type VI secretion. CspV controls biofilm formation through modulation of the second messenger cyclic diguanylate and regulates type VI-mediated interspecies killing in a temperature-dependent manner. Furthermore, a strain lacking cspV had significant defects for attachment and type VI-mediated killing on the surface of the aquatic crustacean Daphnia magna Collectively, these studies reveal that cspV is a major regulator of the temperature downshift response and plays an important role in controlling cellular processes crucial to the infectious cycle of V. cholerae

IMPORTANCE

Little is known about how human pathogens respond and adapt to ever-changing parameters of natural habitats outside the human host and how environmental adaptation alters dissemination. Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, experiences fluctuations in temperature in its natural aquatic habitats and during the infection process. Furthermore, temperature is a critical environmental signal governing the occurrence of V. cholerae and cholera outbreaks. In this study, we showed that V. cholerae reprograms its transcriptome in response to fluctuations in temperature, which results in changes to biofilm formation and type VI secretion system activation. These processes in turn impact environmental survival and the virulence potential of this pathogen.

Molecular Epidemiology and Antibiotic Susceptibility of Vibrio cholerae Associated with a Large Cholera Outbreak in Ghana in 2014

BACKGROUND

Ghana is affected by regular cholera epidemics and an annual average of 3,066 cases since 2000. In 2014, Ghana experienced one of its largest cholera outbreaks within a decade with more than 20,000 notified infections. In order to attribute this rise in cases to a newly emerging strain or to multiple simultaneous outbreaks involving multi-clonal strains, outbreak isolates were characterized, subtyped and compared to previous epidemics in 2011 and 2012.

METHODOLOGY/PRINCIPAL FINDINGS

Serotypes, biotypes, antibiotic susceptibilities were determined for 92 Vibrio cholerae isolates collected in 2011, 2012 and 2014 from Southern Ghana. For a subgroup of 45 isolates pulsed-field gel electrophoresis, multilocus sequence typing and multilocus-variable tandem repeat analysis (MLVA) were performed. Eighty-nine isolates (97%) were identified as ctxB (classical type) positive V. cholerae O1 biotype El Tor and three (3%) isolates were cholera toxin negative non-O1/non-O139 V. cholerae. Among the selected isolates only sulfamethoxazole/trimethoprim resistance was detectable in 2011, while 95% of all 2014 isolates showed resistance towards sulfamethoxazole/trimethoprim, ampicillin and reduced susceptibility to ciprofloxacin. MLVA achieved the highest subtype discrimination, revealing 22 genotypes with one major outbreak cluster in each of the three outbreak years. Apart from those clusters genetically distant genotypes circulate during each annual epidemic.

CONCLUSIONS/SIGNIFICANCE

This analysis suggests different endemic reservoirs of V. cholerae in Ghana with distinct annual outbreak clusters accompanied by the occurrence of genetically distant genotypes. Preventive measures for cholera transmission should focus on aquatic reservoirs. Rapidly emerging multidrug resistance must be monitored closely.

Prevalence and Distribution of Vibrio spp. in Wild Aquatic Birds of the Southern Caribbean Sea, Venezuela, 2011-12

Vibrio spp. are associated with waterbirds mainly in temperate latitudes. We evaluated the prevalence and distribution of Vibrio spp. from fecal samples of resident and migratory aquatic birds collected during October 2011 and March 2012 at two coastal sites in the tropical southern Caribbean Sea. We amplified DNA by PCR in 40% of samples, resulting in 47% and 36% estimated prevalence for resident and migratory birds in Cuare Wildlife Refuge, and 33% and 44% in Margarita Island, respectively. We found nontoxigenic Vibrio cholerae in Cuare Wildlife Refuge with a higher prevalence in resident birds (18%). Our PCR results for Vibrio and V. cholerae were not significantly different between sites or bird migratory status. The 16S rRNA phylogenetic analysis sequences from fecal samples from Cuare Wildlife Refuge were highly similar to V. cholerae and Vibrio vulnificus , whereas sequences from Margarita Island samples formed clusters with species related to the Harveyi clade. Our findings indicate that several species of Vibrio are common in aquatic birds along the southern Caribbean Sea and contribute to our understanding of the role of birds as possible reservoirs of potentially pathogenic bacteria.

El Niño, Climate, and Cholera Associations in Piura, Peru, 1991-2001: A Wavelet Analysis

In Peru, it was hypothesized that epidemic cholera in 1991 was linked to El Niño, the warm phase of El Niño-Southern Oscillation. While previous studies demonstrated an association in 1997-1998, using cross-sectional data, they did not assess the consistency of this relationship across the decade. Thus, how strong or variable an El Niño-cholera relationship was in Peru or whether El Niño triggered epidemic cholera early in the decade remains unknown. In this study, wavelet and mediation analyses were used to characterize temporal patterns among El Niño, local climate variables (rainfall, river discharge, and air temperature), and cholera incidence in Piura, Peru from 1991 to 2001 and to estimate the mediating effects of local climate on El Niño-cholera relationships. The study hypothesis is that El Niño-related connections with cholera in Piura were transient and interconnected via local climate pathways. Overall, our findings provide evidence that a strong El Niño-cholera link, mediated by local hydrology, existed in the latter part of the 1990s but found no evidence of an El Niño association in the earlier part of the decade, suggesting that El Niño may not have precipitated cholera emergence in Piura. Further examinations of cholera epicenters in Peru are recommended to support these results in Piura. For public health planning, the results may improve existing efforts that utilize El Niño monitoring for preparedness during future climate-related extremes in the region.

Evaluation of two methods for direct detection of Fusarium spp. in water

Fusarium is a waterborne fungus that causes severe infections especially in patients with prolonged neutropenia. Traditionally, the detection of Fusarium in water is done by culturing which is difficult and time consuming. A faster method is necessary to prevent exposure of susceptible patients to contaminated water. The objective of this study was to develop a molecular technique for direct detection of Fusarium in water. A direct DNA extraction method from water was developed and coupled to a genus-specific PCR, to detect 3 species of Fusarium (verticillioides, oxysporum and solani). The detection limits were 10 cells/L and 1 cell/L for the molecular and culture methods, respectively. To our knowledge, this is the first method developed to detect Fusarium directly from water.

A luminescent hybridoma-based biosensor for rapid detection of V. cholerae upon induction of calcium signaling pathway

In this study, a hybridoma based biosensor was developed for rapid, sensitive and selective detection of Vibrio cholerae O1 which converts the antibody-antigen binding to bioluminescence light. After investigation on hybridoma performance, the biosensor was constructed by transfecting specific hybridoma cells with aequorin reporter gene and the bioluminescence activities of stable biosensor were measured. The sensitivity of biosensor was as few as 50 CFU/ml and it showed no responses to other entric bacteria. Moreover, the response time of biosensor was estimated in 7th second which means this method is considerably faster than many available detection assays. In addition, this biosensor was successfully applied to V. cholerae detection in environmental samples with no significant loss in sensitivity, demonstrating our proposed biosensor provides a sensitive and reliable method for detection of V. cholerae in natural samples. The application of whole hybridoma cell directly as a sensing element in biosensor construction which mentioned for the first time in present study suggests that hybridoma cells could provide a valuable tool for future studies in both basic and diagnostic sciences and could be considered as a fast and specific sensing element for detection of other pathogens in different applications.

A global map of suitability for coastal Vibrio cholerae under current and future climate conditions

Vibrio cholerae is a globally distributed water-borne pathogen that causes severe diarrheal disease and mortality, with current outbreaks as part of the seventh pandemic. Further understanding of the role of environmental factors in potential pathogen distribution and corresponding V. cholerae disease transmission over time and space is urgently needed to target surveillance of cholera and other climate and water-sensitive diseases. We used an ecological niche model (ENM) to identify environmental variables associated with V. cholerae presence in marine environments, to project a global model of V. cholerae distribution in ocean waters under current and future climate scenarios. We generated an ENM using published reports of V. cholerae in seawater and freely available remotely sensed imagery. Models indicated that factors associated with V. cholerae presence included chlorophyll-a, pH, and sea surface temperature (SST), with chlorophyll-a demonstrating the greatest explanatory power from variables selected for model calibration. We identified specific geographic areas for potential V. cholerae distribution. Coastal Bangladesh, where cholera is endemic, was found to be environmentally similar to coastal areas in Latin America. In a conservative climate change scenario, we observed a predicted increase in areas with environmental conditions suitable for V. cholerae. Findings highlight the potential for vulnerability maps to inform cholera surveillance, early warning systems, and disease prevention and control.

Influence of Environmental Factors on Vibrio spp. in Coastal Ecosystems

Various studies have examined the relationships between vibrios and the environmental conditions surrounding them. However, very few reviews have compiled these studies into cohesive points. This may be due to the fact that these studies examine different environmental parameters, use different sampling, detection, and enumeration methodologies, and occur in diverse geographic locations. The current article is one approach to compile these studies into a cohesive work that assesses the importance of environmental determinants on the abundance of vibrios in coastal ecosystems.

Toxigenic Vibrio cholerae identified in estuaries of Tanzania using PCR techniques

The current study assessed the occurrence of the Vibrio cholerae serogroups O1 and O139 in environmental samples along salinity gradients in three selected estuaries of Tanzania both through culture independent methods and by cultured bacteria. Occurrence of V. cholerae was determined by PCR targeting the V. cholerae outer membrane protein gene ompW. Furthermore, the presence of toxigenic strains and serogroups O1 and O139 was determined using multiplex PCR with specific primers targeting the cholera toxin gene subunit A, ctxA, and serotype specific primers, O1-rfb and O139-rfb, respectively. Results showed that V. cholerae occurred in approximately 10% (n = 185) of both the environmental samples and isolated bacteria. Eight of the bacteria isolates (n = 43) were confirmed as serogroup O1 while one belonged to serogroup O139, the first reported identification of this epidemic strain in East African coastal waters. All samples identified as serogroup O1 or O139 and a number of non-O1/O139 strains were ctxA positive. This study provides in situ evidence of the presence of pathogenic V. cholerae O1 and O139 and a number of V. cholerae non-O1/O139 that carry the cholera toxin gene in estuaries along the coast of Tanzania.

Snapshot of Vibrio parahaemolyticus densities in open and closed shellfish beds in Coastal South Carolina and Mississippi

Vibrio parahaemolyticus is a Gram negative, halophilic bacterium that is ubiquitous in warm, tropical waters throughout the world. It is a major cause of seafood-associated gastroenteritis and is generally associated with consumption of raw or undercooked seafood, especially oysters. This study presents a snapshot of total V. parahaemolyticus densities in surface waters and shellstock American oysters (Crassostrea virginica) from open and closed shellfish harvesting areas, as well as "more rural areas" on two different US coasts, the Atlantic and the Gulf. Sampling was conducted from 2001 to 2003 at five sites near Charleston/Georgetown, SC and at four locations in the Gulfport/Pascagoula, MS area. V. parahaemolyticus numbers were determined by a direct plating method using an alkaline-phosphatase-labeled DNA probe targeting the species-specific thermolabile hemolysin gene (tlh) that was used for identification of bacterial isolates. The greatest difference between the two coasts was salinity; mean salinity in SC surface waters was 32.9 ppt, whereas the mean salinity in MS waters was 19.2 ppt, indicating more freshwater input into MS shellfish harvesting areas during the study period. The mean V. parahaemolyticus numbers in oysters were almost identical between the two states (567.4 vs. 560.1 CFU/g). Bacterial numbers in the majority of surface water samples from both states were at or below the limit of detection (LOD = <10 CFU/mL). The bacterial concentrations determined during this study predict a low public health risk from consumption of oysters in shellfish growing areas on either the Gulf or the Atlantic US coast.

Protein A-conjugated iron oxide nanoparticles for separation ofVibrio choleraefrom water samples

Pathogen separation is of great significance for precise detection and prevention of disease outbreaks. For the first time, protein A conjugated with chitosan-coated iron oxide nanoparticles was prepared for pathogen separation at low concentrations from liquid samples.Vibrio choleraeO1 (VO1) bacteria were used for testing the effectiveness of this conjugate. Transmission electron microscopy (TEM) was used to confirm the presence of captured VO1. The results showed that, after binding with a specific antibody, the conjugate allows separation of VO1 bacteria from water samples at a concentration as low as 10 cfu mL⁻¹. Moreover, the conjugate can be used in parallel with conventional or modern diagnostic tests for quick and accurate detection of pathogens.

Environmental reservoirs and mechanisms of persistence of Vibrio cholerae

It is now well accepted that Vibrio cholerae, the causative agent of the water-borne disease cholera, is acquired from environmental sources where it persists between outbreaks of the disease. Recent advances in molecular technology have demonstrated that this bacterium can be detected in areas where it has not previously been isolated, indicating a much broader, global distribution of this bacterium outside of endemic regions. The environmental persistence of V. cholerae in the aquatic environment can be attributed to multiple intra- and interspecific strategies such as responsive gene regulation and biofilm formation on biotic and abiotic surfaces, as well as interactions with a multitude of other organisms. This review will discuss some of the mechanisms that enable the persistence of this bacterium in the environment. In particular, we will discuss how V. cholerae can survive stressors such as starvation, temperature, and salinity fluctuations as well as how the organism persists under constant predation by heterotrophic protists.

Detection of Vibrio parahaemolyticus, Vibrio vulnificus and Vibrio cholerae with respect to seasonal fluctuations in temperature and plankton abundance

Over a 1-year period, bi-monthly estuarine surface water and plankton samples (63-200 and > 200 μm fractions) were assayed by polymerase chain reaction for the prevalence of total Vibrio parahaemolyticus, V. vulnificus and V. cholerae and select genes associated with clinical strains found in each species. Neither temperature nor plankton abundance was a significant correlate of total V. parahaemolyticus; however, the prevalence of genes commonly associated with clinical strains (trh, tdh, ORF8) increased with temperature and copepod abundance (P < 0.05). The prevalence of total V. vulnificus and the siderophore-related viuB gene also increased with temperature and copepod and decapod abundance (P < 0.001). Temperature and copepod abundance also covaried with the prevalence of V. cholerae (P < 0.05), but there was no significant relationship with ctxA or other genes commonly found in clinical strains. Results show that genes commonly associated with clinical Vibrio strains were more frequently detected in association with chitinous plankton. We conclude that V. parahaemolyticus, V. vulnificus, V. cholerae and subpopulations that harbour genes common to clinical strains respond distinctly to seasonal changes in temperature as well as shifts in the taxonomic composition of discrete plankton fractions.

Detection of Escherichia coli, Salmonella species, and Vibrio cholerae in tap water and bottled drinking water in Isfahan, Iran

BACKGROUND

The quality of drinking water has an important role in human infection and disease. This study was aimed at comparing polymerase chain reaction and culture in detecting Escherichia coli, Salmonella species and Vibrio cholera in tape water and bottled drinking water in various seasons in Isfahan province, Iran.

METHODS

A total of 448 water samples from tap water and bottled mineral water were taken over 6 months, from July 2010 to December 2010, and after filtration, samples were examined by culture and polymerase chain reaction methods for detection of Escherichia coli, Salmonella species, and Vibrio cholerae.

RESULTS

The culture method showed that 34 (7.58%), 4 (0.89%) and 3 (0.66%) of all 448 water samples were positive for Escherichia coli, Salmonella species, and Vibrio cholera, respectively. The uidA gene from Escherichia coli, IpaB gene from Salmonella species, and epsM gene from Vibrio cholera were detected in 38 (26.38%), 5 (3.47%), and 3 (2.08%) of 144 tap-water samples, respectively. Escherichia coli was detected in 8 (2.63%) of 304 samples of bottled drinking water from 5 companies. The water of southern part of Isfahan and company 5 had the highest prevalence of bacteria. The Escherichia coli water contamination was significantly higher (P < 0.05) in the hot seasons (July-August) than cold (November-December) seasons and in company 5 than other companies. There were significant differences (P < 0.05) for the prevalence of bacteria between the tap waters of southern part and tap waters of central part of Isfahan.

CONCLUSIONS

This study showed that the polymerase chain reaction assays can be an extremely accurate, fast, safe, sensitive and specific approach to monitor drinking water quality from purification facilities and bottled water companies. Also, our study confirmed the presence of Escherichia coli, Salmonella species, and Vibrio cholerae as water-borne pathogens in tap water and bottled drinking water of Isfahan, Iran. The present study showed the important public health problem in Isfahan, Iran.

Real-time PCR and NASBA for rapid and sensitive detection of Vibrio cholerae in ballast water

Transport of ballast water is one major factor in the transmission of aquatic organisms, including pathogenic bacteria. The IMO-guidelines of the Convention for the Control and Management of Ships' Ballast Water and Sediments, states that ships are to discharge <1 CFU per 100 ml ballast water of toxigenic Vibrio cholerae, emphasizing the need to establish test methods. To our knowledge, there are no methods sensitive and rapid enough available for cholera surveillance of ballast water. In this study real-time PCR and NASBA methods have been evaluated to specifically detect 1 CFU/100ml of V. cholerae in ballast water. Ballast water samples spiked with V. cholerae cells were filtered and enriched in alkaline peptone water before PCR or NASBA detection. The entire method, including sample preparation and analysis was performed within 7 h, and has the potential to be used for analysis of ballast water for inspection and enforcement control.

Phenotypic and genetic analyses of 111 clinical and environmental O1, O139, and non-O1/O139 Vibrio cholerae strains from different geographical areas

A total of 111 clinical and environmental O1, O139 and non-O1/O139 Vibrio cholerae strains isolated between 1978 and 2008 from different geographical areas were typed using a combination of methods: antibiotic susceptibility, biochemical test, serogroup, serotype, biotype, sequences containing variable numbers of tandem repeats (VNTRs) and virulence genes ctxA and tcpA amplification. As a result of the performed typing work, the strains were organized into four clusters: cluster A1 included clinical O1 Ogawa and O139 serogroup strains (ctxA(+) and tcpA(+)); cluster A2 included clinical non-O1/O139 strains (ctxA(-) and tcpA(-)), as well as environmental O1 Inaba and non-O1/O139 strains (ctxA(-) and tcpA(-)/tcpA(+)); cluster B1 contained two clinical O1 strains and environmental non-O1/O139 strains (ctxA(-) and tcpA(+)/tcpA(-)); cluster B2 contained clinical O1 Inaba and Ogawa strains (ctxA(+) and tcpA(+)). The results of this work illustrate the advantage of combining several typing methods to discriminate between clinical and environmental V. cholerae strains.

Ecology and genetic structure of a northern temperate Vibrio cholerae population related to toxigenic isolates

Although Vibrio cholerae is an important human pathogen, little is known about its populations in regions where the organism is endemic but where cholera disease is rare. A total of 31 independent isolates confirmed as V. cholerae were collected from water, sediment, and oysters in 2008 and 2009 from the Great Bay Estuary (GBE) in New Hampshire, a location where the organism has never been detected. Environmental analyses suggested that abundance correlates most strongly with rainfall events, as determined from data averaged over several days prior to collection. Phenotyping, genotyping, and multilocus sequence analysis (MLSA) revealed a highly diverse endemic population, with clones recurring in both years. Certain isolates were closely related to toxigenic O1 strains, yet no virulence genes were detected. Multiple statistical tests revealed evidence of recombination among strains that contributed to allelic diversity equally as mutation. This relatively isolated population discovered on the northern limit of detection for V. cholerae can serve as a model of natural population dynamics that augments predictive models for disease emergence.

Development of a dry reagent-based triplex PCR for the detection of toxigenic and non-toxigenic Vibrio cholerae

Vibrio cholerae has caused severe outbreaks of cholera worldwide with thousands of recorded deaths annually. Molecular diagnosis for cholera has become increasingly important for rapid detection of cholera as the conventional methods are time-consuming and labour intensive. However, traditional PCR tests still require cold-chain transportation and storage as well as trained personnel to perform, which makes them user-unfriendly. The aim of this study was to develop a thermostabilized triplex PCR test for cholera which is in a ready-to-use form and requires no cold chain. The PCR test specifically detects both toxigenic and non-toxigenic strains of V. cholerae based on the cholera toxin A (ctxA) and outer-membrane lipoprotein (lolB) genes. The thermostabilized triplex PCR also incorporates an internal amplification control that helps to check for PCR inhibitors in samples. PCR reagents and the specific primers were lyophilized into a pellet form in the presence of trehalose, which acts as an enzyme stabilizer. The triplex PCR was validated with 174 bacteria-spiked stool specimens and was found to be 100 % sensitive and specific. The stability of the thermostabilized PCR was evaluated using the Q10 method and it was found to be stable for approximately 7 months at 24 °C. The limit of detection of the thermostabilized triplex PCR assay was 2×104 c.f.u. at the bacterial cell level and 100 pg DNA at the genomic DNA level, comparable to conventional PCR methods. In conclusion, a rapid thermostabilized triplex PCR assay was developed for detecting toxigenic and non-toxigenic V. cholerae which requires minimal pipetting steps and is cold chain-free.

Multiplex polymerase chain reaction-based assay for the specific detection of toxin-producing Vibrio cholerae in fish and fishery products

A multiplex polymerase chain reaction (MPCR)-based assay was developed for the simultaneous detection of Vibrios using the genus-specific RNA polymerase subunit A (rpoA) gene and specific detection of toxin-producing Vibrio cholerae strains using two sets of primer based on cholera toxin subunit A (ctxA) and repeat in toxin subunit A (RtxA)-producing genes. The MPCR method developed is applicable to both the simultaneous and the two-step detection of genus Vibrio total and toxigenic V. cholerae species. This assay was specific as no amplification occurred with the other bacterial pathogens tested. The sensitivity of the assay was tested by artificially spiking the shrimp homogenate with the toxigenic strain of V. cholerae (NICED 16582) in different dilutions. The developed MPCR assay could detect three cells of V. cholerae in 12 h pre-enrichment in APW. The proposed method is rapid, sensitive, and specific for the detection of Vibrio genus as well as toxin-producing V. cholerae strains in environmental samples.

Detection of Vibrio cholerae O1 and O139 in environmental water samples by an immunofluorescent-aggregation assay

Environmental waters are an important reservoir for Vibrio cholerae, and effective surveillance of the pathogen can help to warn of and prevent infection with this potentially fatal pathogen. An immunofluorescent-aggregation (IFAG) assay to detect V. cholerae O1 and O139 was established and evaluated with estuarine water samples. The practical application of this assay was compared with the conventional culture method and real-time PCR. The IFAG method had a sensitivity of 10(3) CFU/ml for detection of V. cholerae O1 and O139 strains in a suspension containing 10 different species of enterobacterial strains (total, 10(5) CFU/ml). Ten fluorescent bacterial aggregate colonies were randomly picked and tested positive in serum agglutination tests for the V. cholerae O1 and O139 strains, showing a high specificity. The enrichment broths of 146 samples of estuarine water were tested, and the percentage positive by the IFAG assay was 19.9% (29/146), which was significantly higher than that of the conventional culture method (10.3%, 15/146; P < 0.01) but lower than that of real-time PCR (29.5%, 43/146; P < 0.01). The coincidence rates of real-time PCR and IFAG detection were decreased with the reduction of the V. cholerae concentration. The IFAG method, with a high specificity and a relatively high sensitivity, may be used for detection and isolation of V. cholerae in environmental water samples.

Comparison between a TaqMan polymerase chain reaction assay and a culture method for ctx-positive Vibrio cholerae detection

The main objective of the present work was to evaluate a real-time polymerase chain reaction (PCR) method to detect toxigenic Vibrio cholerae in Pangasius hypophthalmus, a freshwater fish cultured mainly in South East Asia. A FDA traditional culture method and a real-time PCR method of the ctx gene were used for detection of V. cholerae in spiked samples of pangasius fish. After an overnight enrichment of samples at 37 degrees C in alkaline peptone water, 2 cfu/25 g of fish was detected with both methods. Although both methods were very sensitive, obtaining results with culture methods may take several days, while real-time PCR takes only a few hours. Furthermore, with traditional methods, complementary techniques such as serotyping, although not available for all serogroups, are needed to identify toxigenic V. cholerae. However, with real-time PCR, toxigenic serogroups are detected in only one step after overnight enrichment.

New Biotype of Vibrio cholerae O1 from Clinical Isolates in Surabaya

A surveillance of new pathogenic variants of Vibrio cholerae O1 strains was initiated to identify the emerge and spread throughout Surabaya. Findings from seven years (1994–2000) and from years 2008 until now by using a two-fold surveillance strategy was pursued involving 1) hospital-based case recognition, and 2) environment samples. Rectal swabs and environment samples were transported to ITD-UNAIR, Surabaya for culture and isolates were characterized by serotypic identification and arbitrarily primed PCR fingerprints revealed a group of strains with similar fingerprint patterns that are distinct from those of the current El Tor epidemic strain. These strains have been analyzed by in vitro technique and the group has been denominated the Surabaya-Indonesian variant of V. cholerae O1.

Virulence profile and clonal relationship among the Vibrio cholerae isolates from ground and surface water in a cholera endemic area during rainy season

All the V. cholerae non-O1, non-O139 isolates from ground and surface water samples collected during the rainy season (rainfall contributes significantly in the spread of cholera) contained ompW and a regulatory toxR gene, while many others possessed accessory cholera toxin (ace), hemolysin (hlyA) and outer membrane protein (ompU) genes. All the isolates lacked ctxAB, tcp, zot, rfbO1 and rfbO139 genes. The strains could be grouped into two main clusters colligating the isolates from ground water and surface water samples. The results suggest that surface water harbors various virulent V. cholerae strains that contaminate the ground water due to rain or poor hygienic practices, and result in the emergence of new toxigenic strains for cholera.

Novel PCR-based genotyping method, using genomic variability between repetitive sequences of toxigenic Vibrio cholerae O1 El Tor and O139

A novel genotyping method for toxigenic Vibrio cholerae O1 El Tor and O139 was developed. The method was designed to amplify DNA sequences "sandwiched" between any given pair of repetitive sequences, "V. cholera repeats (VCR)", in highly polymorphic "integron island" of ca. 125 kb in the small chromosome of toxigenic V. cholerae so that the resultant PCR amplicons would present with a strain-specific electrophoretic pattern. The VCR-targeted PCR assay (VCR-PCR) for 37 strains of toxigenic V. cholerae O1 El Tor and O139 revealed that the O1 strains isolated before 1990 showed distinct clonality whereas those isolated after 1990 could be separated into two clones, one consisting of strains isolated from South American countries and another of those from other countries. By contrast, O139 strains were genotypically homogenous regardless of the geographic origin or time of isolation. VCR-PCR therefore would be a robust but rapid method for genotypic differentiation of toxigenic V. cholerae O1 El Tor and O139 strains and to recognize strains with epidemic potential.

Vibrio cholerae non-O1, non-O139 associated with seawater and plankton from coastal marine areas of the Caribbean Sea

The aim of this study was to characterize the virulence properties and the antimicrobial resistance of Vibrio cholerae isolates from a coastal area of the Caribbean Sea. Three V. cholerae isolates were obtained from seawater and plankton using the HP selective medium for Helicobacter pylori. These V. cholerae isolates belonged to the non-O1, non-O139 serogroups and they did not have cholera toxin genes. They were resistant to penicillins and some cephalosporins and were sensitive to netilmicin, tetracyclines, sulfamethoxazole-trimethoprim and quinolones. This is the first study that provides biochemical and molecular evidence of non-O1, non-O139 V. cholerae isolates, non-toxigenic, carrying antibiotic resistance in seawater and plankton from a coastal area of the Caribbean Sea.