Vibrio parahaemolyticusandVibrio vulnificusin South America: water, seafood and human infections

Qualitative microbiome profiling along a wastewater system in Kampala, Uganda

Kampala, the capital city of Uganda, is rapidly expanding without adequate wastewater treatment facilities to accommodate the current estimated population of 1.68 million people. Hence, freshwater bodies and natural ecosystems around the city are heavily polluted with organic and inorganic contaminants. Yet, there is a paucity of data on pathogenic microorganisms, which potentially threatens health of local communities. We performed a qualitative microbial analysis using a whole metagenome sequencing approach encompassing over 150 gigabases of sequencing data to characterize the Nakivubo wastewater system, which includes a wastewater channel and surrounding wetlands. We found that microbial diversity is heterogeneous throughout the system and that three community state types could be differentiated. We showed the presence of various waterborne agents of gastrointestinal infections in humans, which were associated with leakage occurring around two locations along the wastewater channel. Our data indicate that the microbial decontamination capacity of the local wastewater treatment facility was insufficient at the time of sampling, and that several areas of the wetlands were contaminated with human pathogens, indicating that parts of the wetlands are potentially unsafe for urban agriculture.

Modelling of Indicator Escherichia coli Contamination in Sentinel Oysters and Estuarine Water

This study was performed to improve the ability to predict the concentrations of Escherichia coli in oyster meat and estuarine waters by using environmental parameters, and microbiological and heavy metal contamination from shellfish growing area in southern Thailand. Oyster meat (n = 144) and estuarine waters (n = 96) were tested for microbiological and heavy metal contamination from March 2016 to February 2017. Prevalence and mean concentrations of E. coli were 93.1% and 4.6 × 10³ most probable number (MPN)/g in oyster meat, and 78.1% and 2.2 × 10² MPN/100 mL in estuarine water. Average 7-day precipitation, ambient air temperature, and the presence of Salmonella were associated with the concentrations of E. coli in oyster meat (p < 0.05). Raw data (MPN/g of oyster meat and MPN/100 mL of estuarine water) and log-transformed data (logMPN/g of oyster meat and logMPN/100 mL of estuarine water) of E. coli concentrations were examined within two contrasting regression models. However, the more valid predictions were conducted using non-log transformed values. These findings indicate that non-log transformed data can be used for building more accurate statistical models in microbiological food safety, and that significant environmental parameters can be used as a part of a rapid warning system to predict levels of E. coli before harvesting oysters.

Investigation of a Farm-scale Multitrophic Recirculating Aquaculture System with the Addition of Rhodovulum sulfidophilum for Milkfish (Chanos chanos) Coastal Aquaculture

Globally, coastal aquaculture is growing due to the large demand for marine products. Specific impacts caused by coastal aquaculture on the environment include the discharge of culture farm effluents, stress on ground water (the absence of recycling), nutrient pollution, and diseases of cultured animals. Three methods, integrated multitrophic aquaculture (IMTA), recirculating aquaculture system (RAS), and beneficial bacteria for aquaculture, have been developed to solve these problems. In this study, the advantages of IMTA and RAS were integrated to develop a novel multitrophic recirculating aquaculture system (MRAS) to adapt to the farm-scale culturing of milkfish (Chanos chanos). The photosynthetic bacteria Rhodovulum sulfidophilum was added to enhance the performance of the farm-scale milkfish MRAS. This setting could promote growth of beneficial bacteria, such as the nitrogen cycle-associated microbial community and the anoxygenic phototrophic Acidobacteria community. The ammonia level was reduced, and the total phosphorous level was stable in the water recycled in the MRAS. The cyanobacteria, algae, Vibrio, Escherichia, and other potential pathogenic bacteria communities were inhibited in the MRAS. This study provides an effective design of a water recycling aquaculture system. Milkfish, Asian tiger shrimp (Penaeus monodon), Asian hard clam (Meretrix lusoria), and seaweed (Gracilaria sp.) can be cultured and simultaneously produced in the system.

Epidemic Dynamics of Vibrio parahaemolyticus Illness in a Hotspot of Disease Emergence, Galicia, Spain

Galicia in northwestern Spain has been considered a hotspot for Vibrio parahaemolyticus infections. Infections abruptly emerged in 1998 and, over the next 15 years, were associated with large outbreaks caused by strains belonging to a single clone. We report a recent transition in the epidemiologic pattern in which cases throughout the region have been linked to different and unrelated strains. Global genome-wide phylogenetic analysis revealed that most of the pathogenic strains isolated from infections were associated with globally diverse isolates, indicating frequent episodic introductions from disparate and remote sources. Moreover, we identified that the 2 major switches in the epidemic dynamics of V. parahaemolyticus in the regions, the emergence of cases and an epidemiologic shift in 2015-2016, were associated with the rise of sea surface temperature in coastal areas of Galicia. This association may represent a fundamental contributing factor in the emergence of illness linked to these introduced pathogenic strains.

blaNDM-1-producing Vibrio parahaemolyticus and V. vulnificus isolated from recreational beaches in Lagos, Nigeria

Twenty-six strains of Vibrio parahaemolyticus and 14 strains of V. vulnificus isolated from selected beaches in Lagos State, Nigeria, were examined for virulence and antimicrobial resistance genes. The V. parahaemolyticus isolates were further serotyped and subjected to pulsed field gel electrophoresis (PFGE). Five strains of V. vulnificus and one of V. parahaemolyticus carried the New Delhi-metallo-beta-lactamase gene bla_NDM-1, seven strains carried bla_TEM, and four strains of V. vulnificus and one of V. parahaemolyticus carried bla_CMY. Real-time PCR assay for detection of virulence genes tdh and trh in the V. parahaemolyticus isolates showed that five isolates were positive for tdh, two for trh, and one isolate carried both genes. Ten V. parahaemolyticus serogroups and 23 pulsotypes were identified from 26 isolates based on O and K antigens typing and PFGE. Five of the isolates belong to the pandemic strains O1:Kut and O3:K6, and three belonged to the highly virulent O4:Kut serotype. Nineteen of the isolates showed distinct PFGE banding patterns. These results highlighted the importance of Nigerian recreational beaches as reservoirs of antimicrobial resistance genes of global public health interest, such as bla_NDM-1.

Genotypic and phenotypic characterization of Escherichia coli isolated from mollusks in Brazil and the United States

The aim of this study was to determine the serogroups, antimicrobial resistance and genetic diversity of Escherichia coli isolates from samples of bivalve mollusks collected along Santa Catarina coast, Brazil, and from the Chesapeake Bay, Maryland, USA. One hundred forty‐one E. coli isolates were characterized for serogroups with 181 specific O antisera and antimicrobial susceptibility using the disk diffusion method. The genetic diversity was assessed using pulsed‐field gel electrophoresis (PFGE). The results showed that among the isolates, 19.9% were classified as multi‐drug resistant (MDR) and resistance was most frequently observed to cephalothin, nitrofurantoin, and ampicillin. The predominant serogroups were O6, O8, and O38. Some serogroups were recognized as pathogenic E. coli. PFGE dendrograms indicated extensive genetic diversity among the isolates. Although characteristics of the E. coli isolates were highly variable, it is important to note that E. coli belonging to pathogenic serogroups and MDR isolates are present in mollusks of both study areas. This is the first report on the phenotypic and genotypic characterization of E. coli from mollusks from Santa Catarina and the Chesapeake Bay that should encourage studies focusing on comparison of isolates across countries.

Effect of supercritical carbon dioxide processing on Vibrio parahaemolyticus in nutrient broth and in oysters (Crassostrea gigas)

This study aimed to evaluate the technical feasibility of supercritical carbon dioxide (sc-CO₂) treatment for Vibrio parahaemolyticus inactivation in oysters (Crassostrea gigas) and in nutrient broth. For this purpose, a variable-volume reactor was used as experimental system and a 2³ factorial design was adopted considering the mass ratio between carbon dioxide and the product, pressurization and depressurization rate and pressurization cycles. Through statistical analysis of the experimental data, the mass ratio of 1:0.8 (product:carbon dioxide), depressurization rate of 10.0 MPa/min and one cycle of pressurization was determined as the best process condition to eliminate V. parahaemolyticus, and this was the condition used for the inactivation kinetic analysis. Comparison between the inactivation kinetics of V. parahaemolyticus showed that the behavior of this microorganism inactivation depends on the environment in which it operates and its initial count. The results confirm that the supercritical carbon dioxide is effective in inactivating microorganisms in oysters, including pathogenic V. parahaemolyticus, demonstrating the potential of this technology in the food industry.

Vibrio parahaemolyticus Senses Intracellular K+ To Translocate Type III Secretion System 2 Effectors Effectively

Many Gram-negative bacterial symbionts and pathogens employ a type III secretion system (T3SS) to live in contact with eukaryotic cells. Because T3SSs inject bacterial proteins (effectors) directly into host cells, the switching of secretory substrates between translocators and effectors in response to host cell attachment is a crucial step for the effective delivery of effectors. Here, we show that the protein secretion switch of Vibrio parahaemolyticus T3SS2, which is a main contributor to the enteropathogenicity of a food poisoning bacterium, is regulated by two gatekeeper proteins, VgpA and VgpB. In the absence of these gatekeepers, effector secretion was activated, but translocator secretion was abolished, causing the loss of virulence. We found that the K⁺ concentration, which is high inside the host cell but low outside, is a key factor for VgpA- and VgpB-mediated secretion switching. Exposure of wild-type bacteria to K⁺ ions provoked both gatekeeper and effector secretions but reduced the level of secretion of translocators. The secretion protein profile of wild-type bacteria cultured with 0.1 M KCl was similar to that of gatekeeper mutants. Furthermore, depletion of K⁺ ions in host cells diminished the efficiency of T3SS2 effector translocation. Thus, T3SS2 senses the high intracellular concentration of K⁺ of the host cell so that T3SS2 effectors can be effectively injected.

The pathogenesis of many Gram-negative bacterial pathogens arises from a type III secretion system (T3SS), whereby bacterial proteins (effectors) are directly injected into host cells. The injected effectors then modify host cell functions. For effective delivery of effector proteins, bacteria need to both recognize host cell attachment and switch the type of secreted proteins. Here, we identified gatekeeper proteins that play important roles in a T3SS2 secretion switch of Vibrio parahaemolyticus, a causative agent of food-borne gastroenteritis. We also found that K⁺, which is present in high concentrations inside the host cell but in low concentrations outside, is a key factor for the secretion switch. Thus, V. parahaemolyticus senses the high intracellular K⁺ concentration, triggering the effective injection of effectors.

Structure, function and regulation of the thermostable direct hemolysin (TDH) in pandemic Vibrio parahaemolyticus

Vibrio parahaemolyticus is a leading cause of seafood-associated bacterial gastroenteritis. The pathogen produces the thermostable direct hemolysin (TDH), which is the sole cause of the Kanagawa phenomenon (KP), a special β-type haemolysis in the Wagatsuma agar. TDH also exerts several other biological activities, the major includes lethal toxicity, cytotoxicity, and enterotoxicity. The structure and roles of TDH and the transcriptional regulation of tdh genes, are summarized in this review, which will give a better understanding of the pathogenesis of V. parahaemolyticus.

El Niño Southern Oscillation (ENSO) and Health: An Overview for Climate and Health Researchers

The El Niño Southern Oscillation (ENSO) is an important mode of climatic variability that exerts a discernible impact on ecosystems and society through alterations in climate patterns. For this reason, ENSO has attracted much interest in the climate and health science community, with many analysts investigating ENSO health links through considering the degree of dependency of the incidence of a range of climate diseases on the occurrence of El Niño events. Because of the mounting interest in the relationship between ENSO as a major mode of climatic variability and health, this paper presents an overview of the basic characteristics of the ENSO phenomenon and its climate impacts, discusses the use of ENSO indices in climate and health research, and outlines the present understanding of ENSO health associations. Also touched upon are ENSO-based seasonal health forecasting and the possible impacts of climate change on ENSO and the implications this holds for future assessments of ENSO health associations. The review concludes that there is still some way to go before a thorough understanding of the association between ENSO and health is achieved, with a need to move beyond analyses undertaken through a purely statistical lens, with due acknowledgement that ENSO is a complex non-canonical phenomenon, and that simple ENSO health associations should not be expected.

Vibrio spp. infections

Vibrio is a genus of ubiquitous bacteria found in a wide variety of aquatic and marine habitats; of the >100 described Vibrio spp., ~12 cause infections in humans. Vibrio cholerae can cause cholera, a severe diarrhoeal disease that can be quickly fatal if untreated and is typically transmitted via contaminated water and person-to-person contact. Non-cholera Vibrio spp. (for example, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio vulnificus) cause vibriosis - infections normally acquired through exposure to sea water or through consumption of raw or undercooked contaminated seafood. Non-cholera bacteria can lead to several clinical manifestations, most commonly mild, self-limiting gastroenteritis, with the exception of V. vulnificus, an opportunistic pathogen with a high mortality that causes wound infections that can rapidly lead to septicaemia. Treatment for Vibrio spp. infection largely depends on the causative pathogen: for example, rehydration therapy for V. cholerae infection and debridement of infected tissues for V. vulnificus-associated wound infections, with antibiotic therapy for severe cholera and systemic infections. Although cholera is preventable and effective oral cholera vaccines are available, outbreaks can be triggered by natural or man-made events that contaminate drinking water or compromise access to safe water and sanitation. The incidence of vibriosis is rising, perhaps owing in part to the spread of Vibrio spp. favoured by climate change and rising sea water temperature.

Detection of Total and Pathogenic Vibrio parahaemolyticus in Shellfish Growing along the South Yellow Sea and the East China Sea

This study was conducted to monitor the densities of total and pathogenic Vibrio parahaemolyticus in 300 samples of nine shellfish species harvested from the coasts of the South Yellow Sea and the East China Sea (N 23° to 34°, E 116° to 124°), People's Republic of China, between May and October 2015. Total V. parahaemolyticus densities were measured, and V. parahaemolyticus isolates were biochemically identified with probes for the thermostable direct hemolysin gene (tdh) and the thermostable direct hemolysin-related hemolysin gene (trh). We found that 202 of the 300 samples were positive for V. parahaemolyticus from all the sites: 58 of the 100 samples from the Fujian province, 71 of the 100 samples from the Zhejiang province, and 73 of the 100 samples from the Jiangsu province. In most (170) of the 300 samples, V. parahaemolyticus densities were 0.3 to 10 most probable number (MPN)/g; five lots exceeded 110 MPN/g, and two lots were estimated at 110 MPN/g. Among the 202 V. parahaemolyticus strains, only one was trh positive. Densities of V. parahaemolyticus in these shellfish were temperature dependent, with highest densities in June and July. Among the nine mollusk species, V. parahaemolyticus was most abundant in the agemaki clam (Sinonovacula constricta). The highest and lowest V. parahaemolyticus prevalences were found in oriental cyclina (Cyclina sinensis, 93.8%) and mussels (Mytilus edulis, 28.1%), respectively. Overall, although V. parahaemolyticus is widely distributed in marine environments, the density of V. parahaemolyticus was low and the prevalence of the main virulence factor was very low in shellfish along the coasts of the South Yellow Sea and East China Sea, which is important from a public health perspective. Data presented here will be useful for correlational research and can be utilized for developing risk management plans that establish food safety guidelines for V. parahaemolyticus in Chinese shellfish.

Responses of Mytilus galloprovincialis hemocytes to environmental strains of Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio vulnificus

Marine bivalves are exposed to different types of bacteria in the surrounding waters, in particular of the Vibrio genus. In the hemocytes of the mussel Mytilus spp. immune responses to different vibrios have been largely characterized. However, little information is available on the hemocyte responses to human pathogenic vibrios commonly detected in coastal waters and bivalve tissues that are involved in seafood-borne diseases. In this work, functional parameters of the hemocytes from the Mediterranean mussel M. galloprovincialis were evaluated in response to in vitro challenge with different vibrios isolated from environmental samples of the Adriatic sea (Italy): V. parahaemolyticus Conero, V. alginolyticus 1513 and V. vulnificus 509. V. parahaemolyticus ATCC 43996 was used for comparison. At the 50:1 bacteria hemocyte ratio, only V. parahaemolyticus strains induced significant lysosomal membrane destabilisation. Stimulation of extracellular lysozyme release, total ROS, O₂^- and NO production were observed, although to different extents and with distinct time courses for different vibrios, V. vulnificus 509 in particular. Further comparisons between V. parahaemolyticus Conero and V. vulnificus 509 showed that only the latter induced dysregulation of the phosphorylation state of p38 MAP Kinase and apoptotic processes. The results indicate that mussel hemocytes can mount an efficient immune response towards V. parahaemolyticus and V. alginolyticus strains, whereas V. vulnificus 509 may affect the hemocyte function. This is the first report on immune responses of mussels to local environmental isolates of human pathogenic vibrios. These data reinforce the hypothesis that Mytilus hemocytes show specific responses to different vibrio species and strains.

The cytotoxic type 3 secretion system 1 of Vibrio rewires host gene expression to subvert cell death and activate cell survival pathways

Bacterial effectors potently manipulate host signaling pathways. The marine bacterium Vibrio parahaemolyticus (V. para) delivers effectors into host cells through two type 3 secretion systems (T3SSs). T3SS1 is vital for V. para survival in the environment, whereas T3SS2 causes acute gastroenteritis in human hosts. Although the natural host is undefined, T3SS1 effectors attack highly conserved cellular processes and pathways to orchestrate nonapoptotic cell death. To understand how the concerted action of T3SS1 effectors globally affects host cell signaling, we compared gene expression changes over time in primary fibroblasts infected with V. para that have a functional T3SS1 (T3SS1⁺) to those in cells infected with V. para lacking T3SS1 (T3SS1^-). Overall, the host transcriptional response to both T3SS1⁺ and T3SS1^-V. para was rapid, robust, and temporally dynamic. T3SS1 rewired host gene expression by specifically altering the expression of 398 genes. Although T3SS1 effectors targeted host cells at the posttranslational level to cause cytotoxicity, V. para T3SS1 also precipitated a host transcriptional response that initially activated cell survival and repressed cell death networks. The increased expression of several key prosurvival transcripts mediated by T3SS1 depended on a host signaling pathway that is silenced posttranslationally later in infection. Together, our analysis reveals a complex interplay between the roles of T3SS1 as both a transcriptional and posttranslational manipulator of host cell signaling.

Vibrio Parahaemolyticus: A Review on Distribution, Pathogenesis, Virulence Determinants and Epidemiology

Vibrio parahaemolyticus is a Gram-negative, halophilic bacterium isolated from marine environments globally. After the consumption of contaminated seafood, V. parahaemolyticus causes acute gastroenteritis. To initiate infection, a wide range of virulence factors are required. A complex group of genes is known to participate in the pathogenicity of V. parahaemolyticus; however, to understand the full mechanism of infection, extensive research is yet required. V. parahaemolyticus has become the leading cause of seafood-related gastroenteritis in Japan, the United States and several other parts of the world. In addition, outbreaks caused by the pandemic clone of this organism are escalating and spreading universally. To minimize the risk of V. parahaemolyticus infection and warrant the safety of seafood, collaboration between governments and scientists is required. We herein provide an updated review of the pathogenicity determinants and distribution of V. parahaemolyticus to deliver a better understanding of the significance of V. parahaemolyticus and its host-pathogen interactions.

Development of a regulatable expression system for the functional study of Vibrio vulnificus essential genes

We developed a regulatable gene expression system for Vibrio vulnificus, which contains a lacIq-pTrc cassette. Monomeric red fluorescence protein (mRFP) was used as a reporter to test this system. The results showed that this system tightly controlled the expression of mRFP without leaky expression and was suitable for the controlled expression of genes encoding recombinant proteins in V. vulnificus. To demonstrate the utility of this system, a dominant negative form of V. vulnificus VVMO6_RS04990, a homolog of Escherichia coli LolD that is essential in lipoprotein transport and membrane biogenesis, was inducibly expressed. Expression of the dominant negative LolD homolog, which has a mutation in the ATPase domain, resulted in a growth defect in V. vulnificus cells and impaired cell envelope stability. This result suggests that the V. vulnificus LolD homolog plays a role in cell envelope biogenesis. This tight and titratable expression system will therefore be a valuable tool for the study of essential genes in V. vulnificus.

Transcriptome analysis of the effect of polyunsaturated fatty acids against Vibrio vulnificus infection in Oreochromis niloticus

Vibrio vulnificus infection causes severe economic losses in Oreochromis niloticus aquaculture by inducing pro-inflammatory cytokines, that lead to inflammation and mortality. Omega-3 fatty acids, such as Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA), have been reported for their anti-inflammatory and antibacterial abilities in murine and zebrafish models. However, the anti-inflammatory and antibacterial functions of DHA and EPA in commercial aquaculture organisms such as Oreochromis niloticus remain unknown. The present study demonstrates antibacterial function and transcriptional modulation of inflammation-associated genes by DHA and EPA in Vibrio vulnificus infection in Oreochromis niloticus fish models. The administration of EPA or DHA improved the Oreochromis niloticus survival rate against Vibrio vulnificus infection. The induction of proinflammatory cytokines, Interleukin (IL)-1β, IL-6, Tumor necrosis factor (TNF)-α, and Toll-like receptor (TLR)-2 by Vibrio vulnificus was suppressed in fish that were administered DHA. Bacterial membrane disruption and the killing of Vibrio vulnificus by EPA and DHA was observed using SEM, TEM, and cytoplasm leakage studies. In silico analysis of the transcription profile in Ingenuity Pathway Analysis software showed that DHA may enhance anti-Vibrio vulnificus activity in Oreochromis niloticus via the activation of peroxisome proliferator-activated receptor α (PPARα) to inhibit nuclear factor kappa B and suppress hepatocyte nuclear factor 4 α (HNF4α). In summary, the results of the present study demonstrated that DHA and EPA reduce the severity of Vibrio vulnificus infection and increase the survival rate of Oreochromis niloticus.

LptD is a promising vaccine antigen and potential immunotherapeutic target for protection against Vibrio species infection

Outer membrane proteins (OMPs) are unique to Gram-negative bacteria. Several features, including surface exposure, conservation among strains and ability to induce immune responses, make OMPs attractive targets for using as vaccine antigens and immunotherapeutics. LptD is an essential OMP that mediates the final transport of lipopolysaccharide (LPS) to outer leaflet. The protein in Vibrio parahaemolyticus was identified to have immunogenicity in our previous report. In this study, broad distribution, high conservation and similar surface-epitopes of LptD were found among the major Vibrio species. LptD was further revealed to be associated with immune responses, and it has a strong ability to stimulate antibody response. More importantly, it conferred 100% immune protection against lethal challenge by V. parahaemolyticus in mice when the mice were vaccinated with LptD, and this finding was consistent with the observation of efficient clearance of bacteria in vaccination mice. Strikingly, targeting of bacteria by the LptD antibody caused significant decreases in both the growth and LPS level and an increase in susceptibility to hydrophobic antibiotics. These findings were consistent with those previously obtained in lptD-deletion bacteria. These data demonstrated LptD is a promising vaccine antigens and a potential target for antibody-based therapy to protect against Vibrio infections.