Vibrio vulnificus: death on the half shell. A personal journey with the pathogen and its ecology

A One-Step RPA-CRISPR Assay Using crRNA Based on Suboptimal Protospacer Adjacent Motif for Vibrio vulnificus Detection

Vibrio vulnificus is a hazardous foodborne pathogen responsible for approximately 95% of seafood-related deaths. This highlights the urgent requirement for specialized detection tools to be developed and used by food enterprises and food safety authorities. The DETECTR (DNA endonuclease targeted CRISPR trans reporter) system that combines CRISPR/Cas and recombinase polymerase amplification (RPA) has been utilized to develop a molecular detection assay for V. vulnificus. However, because the incompatibility between RPA and Cas12a cleavage has not been addressed, it is a two-step assay that lacks convenience and presents contamination risk. Here, we developed a one-step RPA-CRISPR assay for V. vulnificus using a special crRNA targeting a sequence with a suboptimal protospacer adjacent motif (PAM). The entire assay, conducted at 37°C, takes only 40-60 min, yields results visualized under blue light, and exhibits exceptional specificity and sensitivity (detecting 4 pathogen genome copies per reaction). This study offers a valuable tool for detecting V. vulnificus, aiding in foodborne infection prevention, and exemplifies one-step RPA-CRISPR assays managing Cas-cleavage activity through PAM adjustments.

Public health aspects of Vibrio spp. related to the consumption of seafood in the EU

Vibrio parahaemolyticus, Vibrio vulnificus and non-O1/non-O139 Vibrio cholerae are the Vibrio spp. of highest relevance for public health in the EU through seafood consumption. Infection with V. parahaemolyticus is associated with the haemolysins thermostable direct haemolysin (TDH) and TDH-related haemolysin (TRH) and mainly leads to acute gastroenteritis. V. vulnificus infections can lead to sepsis and death in susceptible individuals. V. cholerae non-O1/non-O139 can cause mild gastroenteritis or lead to severe infections, including sepsis, in susceptible individuals. The pooled prevalence estimate in seafood is 19.6% (95% CI 13.7-27.4), 6.1% (95% CI 3.0-11.8) and 4.1% (95% CI 2.4-6.9) for V. parahaemolyticus, V. vulnificus and non-choleragenic V. cholerae, respectively. Approximately one out of five V. parahaemolyticus-positive samples contain pathogenic strains. A large spectrum of antimicrobial resistances, some of which are intrinsic, has been found in vibrios isolated from seafood or food-borne infections in Europe. Genes conferring resistance to medically important antimicrobials and associated with mobile genetic elements are increasingly detected in vibrios. Temperature and salinity are the most relevant drivers for Vibrio abundance in the aquatic environment. It is anticipated that the occurrence and levels of the relevant Vibrio spp. in seafood will increase in response to coastal warming and extreme weather events, especially in low-salinity/brackish waters. While some measures, like high-pressure processing, irradiation or depuration reduce the levels of Vibrio spp. in seafood, maintaining the cold chain is important to prevent their growth. Available risk assessments addressed V. parahaemolyticus in various types of seafood and V. vulnificus in raw oysters and octopus. A quantitative microbiological risk assessment relevant in an EU context would be V. parahaemolyticus in bivalve molluscs (oysters), evaluating the effect of mitigations, especially in a climate change scenario. Knowledge gaps related to Vibrio spp. in seafood and aquatic environments are identified and future research needs are prioritised.

Antibiotic resistance trends among Vibrio vulnificus and Vibrio parahaemolyticus isolated from the Chesapeake Bay, Maryland: a longitudinal study

Antibiotics are often used to treat severe Vibrio infections, with third-generation cephalosporins and tetracyclines combined or fluoroquinolones alone being recommended by the US Centers for Disease Control and Prevention. Increases in antibiotic resistance of both environmental and clinical vibrios are of concern; however, limited longitudinal data have been generated among environmental isolates to inform how resistance patterns may be changing over time. Hence, we evaluated long-term trends in antibiotic resistance of vibrios isolated from Chesapeake Bay waters (Maryland) across two 3-year sampling periods (2009-2012 and 2019-2022). Vibrio parahaemolyticus (n = 134) and Vibrio vulnificus (n = 94) toxR-confirmed isolates were randomly selected from both sampling periods and tested for antimicrobial susceptibility against eight antibiotics using the Kirby-Bauer disk diffusion method. A high percentage (94%-96%) of V. parahaemolyticus isolates from both sampling periods were resistant to ampicillin and only 2%-6% of these isolates expressed intermediate resistance or resistance to third-generation cephalosporins, amikacin, tetracycline, and trimethoprim-sulfamethoxazole. Even lower percentages of resistant V. vulnificus isolates were observed and those were mostly recovered from 2009 to 2012, however, the presence of multiple virulence factors was observed. The frequency of multi-drug resistance was relatively low (6%-8%) but included resistance against antibiotics used to treat severe vibriosis in adults and children. All isolates were susceptible to ciprofloxacin, a fluoroquinolone, indicating its sustained efficacy as a first-line agent in the treatment of severe vibriosis. Overall, our data indicate that antibiotic resistance patterns among V. parahaemolyticus and V. vulnificus recovered from the lower Chesapeake Bay have remained relatively stable since 2009.IMPORTANCEVibrio spp. have historically been susceptible to most clinically relevant antibiotics; however, resistance and intermediate-resistance have been increasingly recorded in both environmental and clinical isolates. Our data showed that while the percentage of multi-drug resistance and resistance to antibiotics was relatively low and stable across time, some Vibrio isolates displayed resistance and intermediate resistance to antibiotics typically used to treat severe vibriosis (e.g., third-generation cephalosporins, tetracyclines, sulfamethoxazole-trimethoprim, and aminoglycosides). Also, given the high case fatality rates observed with Vibrio vulnificus infections, the presence of multiple virulence factors in the tested isolates is concerning. Nevertheless, the continued susceptibility of all tested isolates against ciprofloxacin, a fluoroquinolone, is indicative of its use as an effective first-line treatment of severe Vibrio spp. infections stemming from exposure to Chesapeake Bay waters or contaminated seafood ingestion.

Environmental and Sublethal Concentrations of Polystyrene Nanoplastics Induced Antioxidant System, Transcriptomic Responses, and Disturbed Gut Microbiota in Oyster Magallana Hongkongensis

Nanoplastics (NPs) are emerging contaminants having persistent nature, diverse ecological impacts, and potential food safety risks. Here, we examined the ecotoxicity of 80 nm polystyrene nanoplastics (PS-NPs) at environmentally relevant concentrations (ERCs, 10 and 100 μg/L), and sublethal concentrations (SLCs, 500 and 2500 μg/L) in Magallana hongkongensis. Results showed that SLCs significantly (p < 0.05) increased superoxide dismutase (SOD), catalase (CAT), and alkaline phosphatase (AKP) activities and altered tnfα, cat, gst, sod, and se-gpx genetic expressions. Further, PS-NP exposure at both levels reduced beneficial bacteria and increased potentially pathogenic bacteria in the gut. In transcriptomic analysis, 5118 and 4180 differentially expressed genes (DEGs) were identified at ERCs, while 5665 and 4817 DEGs were found at SLCs, respectively. Upregulated DEGs enriched lysosomes, ABC transporters, and apoptosis pathways, while downregulated DEGs enriched ribosomal pathways. Overall, ERCs significantly altered gut microbiota and transcriptomic responses, while SLCs, in addition, also impacted the antioxidant and immune systems.

Increased incidence of vibriosis in Maryland, U.S.A., 2006-2019

BACKGROUND

Vibrio spp. naturally occur in warm water with moderate salinity. Infections with non-cholera Vibrio (vibriosis) cause an estimated 80,000 illnesses and 100 fatalities each year in the United States. Climate associated changes to environmental parameters in aquatic ecosystems are largely promoting Vibrio growth, and increased incidence of vibriosis is being reported globally. However, vibriosis trends in the northeastern U.S. (e.g., Maryland) have not been evaluated since 2008.

METHODS

Vibriosis case data for Maryland (2006-2019; n = 611) were obtained from the COVIS database. Incidence rates were calculated using U.S. Census Bureau population estimates for Maryland. A logistic regression model, including region, age group, race, gender, occupation, and exposure type, was used to estimate the likelihood of hospitalization.

RESULTS

Comparing the 2006-2012 and 2013-2019 periods, there was a 39% (p = 0.01) increase in the average annual incidence rate (per 100,000 population) of vibriosis, with V. vulnificus infections seeing the greatest percentage increase (53%, p = 0.01), followed by V. parahaemolyticus (47%, p = 0.05). The number of hospitalizations increased by 58% (p = 0.01). Since 2010, there were more reported vibriosis cases with a hospital duration ≥10 days. Patients from the upper eastern shore region and those over the age of 65 were more likely (OR = 6.8 and 12.2) to be hospitalized compared to other patients.

CONCLUSIONS

Long-term increases in Vibrio infections, notably V. vulnificus wound infections, are occurring in Maryland. This trend, along with increased rates in hospitalizations and average hospital durations, underscore the need to improve public awareness, water monitoring, post-harvest seafood interventions, and environmental forecasting ability.

Genome analysis of clinical genotype Vibrio vulnificus isolated from seafood in Mangaluru Coast, India provides insights into its pathogenicity

Vibrio vulnificus an opportunistic human pathogen native to marine/estuarine environment, is one of the leading causes of death due to seafood consumption and exposure of wounds to seawater worldwide. The present study involves the whole genome sequence analysis of an environmental strain of V. vulnificus (clinical genotype) isolated from seafood along the Mangaluru coast of India. The sequenced genome data was subjected to in-silico analysis of phylogeny, virulence genes, antimicrobial resistance determinants, and secretary proteins using suitable bioinformatics tools. The sequenced isolate had an overall genome length of 4.8 Mb and GC content of 46% with 4400 coding DNA sequences. The sequenced strain belongs to a new sequence type (Multilocus sequence typing) and was also found to branch with a phylogenetic lineage that groups the most infectious strains of V. vulnificus. The seafood isolate had complete genes involved in conferring serum resistance yet showed limited serum resistance. The study identified several genes against the antibiotics that are commonly used in their treatment, highlighting the need for alternative treatments. Also, the secretory protein analysis revealed genes associated with major pathways like ABC transporters, two-component systems, quorum sensing, biofilm formation, cationic antimicrobial peptide (CAMP) resistance, and others that play a critical role in the pathogenesis of the V. vulnificus. To the best of our knowledge, this is the first report of a detailed analysis of the genomic information of a V. vulnificus isolated from the Indian subcontinent and provides evidence that raises public health concerns about the safety of seafood.

Cyanobacterial Harmful Algal Bloom Toxin Microcystin and Increased Vibrio Occurrence as Climate-Change-Induced Biological Co-Stressors: Exposure and Disease Outcomes via Their Interaction with Gut-Liver-Brain Axis

The effects of global warming are not limited to rising global temperatures and have set in motion a complex chain of events contributing to climate change. A consequence of global warming and the resultant climate change is the rise in cyanobacterial harmful algal blooms (cyano-HABs) across the world, which pose a threat to public health, aquatic biodiversity, and the livelihood of communities that depend on these water systems, such as farmers and fishers. An increase in cyano-HABs and their intensity is associated with an increase in the leakage of cyanotoxins. Microcystins (MCs) are hepatotoxins produced by some cyanobacterial species, and their organ toxicology has been extensively studied. Recent mouse studies suggest that MCs can induce gut resistome changes. Opportunistic pathogens such as Vibrios are abundantly found in the same habitat as phytoplankton, such as cyanobacteria. Further, MCs can complicate human disorders such as heat stress, cardiovascular diseases, type II diabetes, and non-alcoholic fatty liver disease. Firstly, this review describes how climate change mediates the rise in cyanobacterial harmful algal blooms in freshwater, causing increased levels of MCs. In the later sections, we aim to untangle the ways in which MCs can impact various public health concerns, either solely or in combination with other factors resulting from climate change. In conclusion, this review helps researchers understand the multiple challenges brought forth by a changing climate and the complex relationships between microcystin, Vibrios, and various environmental factors and their effect on human health and disease.

Vibrio Infections and the Twenty-First Century

The Vibrionaceae is a highly diverse family of aquatic bacteria. Some members of this ubiquitous group can cause a variety of diseases in humans ranging from cholera caused by Vibrio cholerae, severe septicemia caused by Vibrio vulnificus, to acute gastroenteritis by Vibrio parahaemolyticus. Planet Earth is experiencing unprecedented changes of planetary scale associated with climate change. These environmental perturbations paired with overpopulation and pollution are increasing the distribution of pathogenic Vibrios and exacerbating the risk of causing infections. In this chapter, we discuss various aspects of Vibrio infections within the context of the twenty-first century with a major emphasis on the aforementioned pathogenic species. Overall, we believe that the twenty-first century is posed to be both one full of challenges due to the rise of these pathogens, and also a catalyst for innovative and groundbreaking discoveries.

Vibrio floridensis sp. nov., a novel species closely related to the human pathogen Vibrio vulnificus isolated from a cyanobacterial bloom

A Gram-stain-negative, rod-shaped bacterial strain, designated Vibrio floridensis IRLE0018 (=NRRL B-65642=NCTC 14661), was isolated from a cyanobacterial bloom along the Indian River Lagoon (IRL), a large and highly biodiverse estuary in eastern Florida (USA). The results of phylogenetic, biochemical, and phenotypic analyses indicate that this isolate is distinct from species of the genus Vibrio with validly published names and is the closest relative to the emergent human pathogen, Vibrio vulnificus. Here, we present the complete genome sequence of V. floridensis strain IRLE0018 (4 535 135 bp). On the basis of the established average nucleotide identity (ANI) values for the determination of different species (ANI <95 %), strain IRLE0018, with an ANI of approximately 92 % compared with its closest relative, V. vulnificus, represents a novel species within the genus Vibrio. To our knowledge, this represents the first time this species has been described. The results of genomic analyses of V. floridensis IRLE0018 indicate the presence of antibiotic resistance genes and several known virulence factors, however, its pathogenicity profile (e.g. survival in serum, phagocytosis avoidance) reveals limited virulence potential of this species in contrast to V. vulnificus.

The Aer2 chemoreceptor from Vibrio vulnificus is a tri-PAS-heme oxygen sensor

The marine pathogen Vibrio vulnificus senses and responds to environmental stimuli via two chemosensory systems and 42-53 chemoreceptors. Here, we present an analysis of the V. vulnificus Aer2 chemoreceptor, VvAer2, which is the first V. vulnificus chemoreceptor to be characterized. VvAer2 is related to the Aer2 receptors of other gammaproteobacteria, but uncharacteristically contains three PAS domains (PAS1-3), rather than one or two. Using an E. coli chemotaxis hijack assay, we determined that VvAer2, like other Aer2 receptors, senses and responds to O₂ . All three VvAer2 PAS domains bound pentacoordinate b-type heme and exhibited similar O₂ affinities. PAS2 and PAS3 both stabilized O₂ via conserved Iβ-Trp residues, but PAS1, which was easily oxidized in vitro, was unaffected by Iβ-Trp replacement. Our results support a model in which PAS1 is largely dispensable for O₂ -mediated signaling, whereas PAS2 modulates PAS3 signaling, and PAS3 signals to the downstream domains. Each PAS domain appeared to be positionally optimized, because PAS swapping caused altered signaling properties, and neither PAS1 nor PAS2 could replace PAS3. Our findings strengthen previous conclusions that Aer2 receptors are O₂ sensors, but with distinct N-terminal domain arrangements that facilitate, modulate and tune responses based on environmental signals.

Prior exposure to microcystin alters host gut resistome and is associated with dysregulated immune homeostasis in translatable mouse models

A strong association between exposure to the common harmful algal bloom toxin microcystin and the altered host gut microbiome has been shown. We tested the hypothesis that prior exposure to the cyanotoxin microcystin-LR may alter the host resistome. We show that the mice exposed to microcystin-LR had an altered microbiome signature that harbored antibiotic resistance genes. Host resistome genotypes such as mefA, msrD, mel, ant6, and tet40 increased in diversity and relative abundance following microcystin-LR exposure. Interestingly, the increased abundance of these genes was traced to resistance to common antibiotics such as tetracycline, macrolides, glycopeptide, and aminoglycosides, crucial for modern-day treatment of several diseases. Increased abundance of these genes was positively associated with increased expression of PD1, a T-cell homeostasis marker, and pleiotropic inflammatory cytokine IL-6 with a concomitant negative association with immunosurveillance markers IL-7 and TLR2. Microcystin-LR exposure also caused decreased TLR2, TLR4, and REG3G expressions, increased immunosenescence, and higher systemic levels of IL-6 in both wild-type and humanized mice. In conclusion, the results show a first-ever characterization of the host resistome following microcystin-LR exposure and its connection to host immune status and antimicrobial resistance that can be crucial to understand treatment options with antibiotics in microcystin-exposed subjects in clinical settings.

The Vibrio vulnificus stressosome is an oxygen-sensor involved in regulating iron metabolism

Stressosomes are stress-sensing protein complexes widely conserved among bacteria. Although a role in the regulation of the general stress response is well documented in Gram-positive bacteria, the activating signals are still unclear, and little is known about the physiological function of stressosomes in the Gram-negative bacteria. Here we investigated the stressosome of the Gram-negative marine pathogen Vibrio vulnificus. We demonstrate that it senses oxygen and identified its role in modulating iron-metabolism. We determined a cryo-electron microscopy structure of the VvRsbR:VvRsbS stressosome complex, the first solved from a Gram-negative bacterium. The structure points to a variation in the VvRsbR and VvRsbS stoichiometry and a symmetry breach in the oxygen sensing domain of VvRsbR, suggesting how signal-sensing elicits a stress response. The findings provide a link between ligand-dependent signaling and an output – regulation of iron metabolism - for a stressosome complex.

A cryo-electron microscopy reconstruction of a stressosome complex from a Gram-negative bacterium, Vibrio vulnificus, reveals variations in subunit composition and symmetry, which could serve to adjust the activation threshold in the response to low levels of oxygen and starvation.

Loss of the acetate switch in Vibrio vulnificus enhances predation defence against Tetrahymena pyriformis

Vibrio vulnificus is an opportunistic human pathogen and autochthonous inhabitant of coastal marine environments, where the bacterium is under constant predation by heterotrophic protists or protozoans. As a result of this selection pressure, genetic variants with antipredation mechanisms are selected for and persist in the environment. Such natural variants may also be pathogenic to animal or human hosts, making it important to understand these defense mechanisms. To identify antipredator strategies, 13 V. vulnificus strains of different genotypes isolated from diverse environments were exposed to predation by the ciliated protozoan Tetrahymena pyriformis, and only strain ENV1 was resistant to predation. Further investigation of the cell-free supernatant showed that ENV1 acidifies the environment by the excretion of organic acids, which are toxic to T. pyriformis. As this predation resistance was dependent on the availability of iron, transcriptomes of V. vulnificus in iron-replete and iron-deplete conditions were compared. This analysis revealed that ENV1 ferments pyruvate and the resultant acetyl-CoA leads to acetate synthesis under aerobic conditions, a hallmark of overflow metabolism. The anaerobic respiration global regulator arcA was upregulated when iron was available. An ΔarcA deletion mutant of ENV1 accumulated less acetate and, importantly, was sensitive to grazing by T. pyriformis. Based on the transcriptome response and quantification of metabolites, we conclude that ENV1 has adapted to overflow metabolism and has lost a control switch that shifts metabolism from acetate excretion to acetate assimilation, enabling it to excrete acetate continuously. We show that overflow metabolism and the acetate switch contribute to prey-predator interactions.

IMPORTANCE Bacteria in the environment, including Vibrio spp., interact with protozoan predators. To defend against predation, bacteria evolve antipredator mechanisms ranging from changing morphology, biofilm formation, and secretion of toxins or virulence factors. Some of these adaptations may result in strains that are pathogenic to humans. Therefore, it is important to study predator defense strategies of environmental bacteria. V. vulnificus thrives in coastal waters and infects humans. Very little is known about the defense mechanisms V. vulnificus expresses against predation. Here, we show that a V. vulnificus strain (ENV1) has rewired the central carbon metabolism, enabling the production of excess organic acid that is toxic to the protozoan predator T. pyriformis. This is a previously unknown mechanism of predation defense that protects against protozoan predators.

Antimicrobial and Genetic Profiles of Vibrio vulnificus and Vibrio parahaemolyticus Isolated From the Maryland Coastal Bays, United States

Vibrio vulnificus and V. parahaemolyticus, found naturally in marine and estuarine environments, are the leading cause of seafood associated gastrointestinal illness and death. Consumption of improperly cooked crabs and handling of live crabs are potential routes of exposure to pathogenic bacteria such as V. vulnificus and V. parahaemolyticus. Little information is available on serotype genetic and antimicrobial profiles of V. vulnificus and V. parahaemolyticus recovered from Maryland estuaries. The aim of the present study was to determine the serotype of V. parahaemolyticus, evaluate antimicrobial susceptibility and genetic profiles of V. vulnificus and V. parahaemolyticus isolated from water and blue crab (Callinectes sapidus) samples collected from the Maryland Coastal Bays. One hundred and fifty (150) PCR confirmed V. parahaemolyticus including 52 tdh⁺ (pathogenic) and 129 V. vulnificus strains were tested for susceptibility to twenty (20) different antibiotics chosen by clinical usage for Vibrio species. The O serogroups were determined using an agglutination test with V. parahaemolyticus antisera. Pulsed-field gel electrophoresis (PFGE) was used for molecular subtyping to investigate the genetic diversity among tested strains. The most prevalent serotypes were O5 (33.3%), O3 (18.7%) and O1 (14.7%). More than 41% of all tested Vibrio isolates were resistant to three or more antibiotics. Cephalothin showed the highest resistance (42% and 61%), followed by cefoxitin (42% and 31%) and ceftazidime (36% and 29%) for V. vulnificus and V. parahaemolyticus, respectively. Most strains (99–100%) were susceptible to ampicillin/sulbactam, levofloxacin, piperacillin, piperacillin/tazobactam, and tetracycline. Fifty percent (50%) of the cephalothin resistant strains were crab isolates. Vibrio vulnificus and V. parahaemolyticus isolates demonstrated a high genetic diversity and 31% of V. vulnificus and 16% of V. parahaemolyticus strains were PFGE untypeable. No correlations were found between the V. parahaemolyticus serotype, pathogenicity, genetic and antimicrobial resistance profiles of both species of Vibrio. The observed high multiple drug resistance of V. vulnificus and V. parahaemolyticus from blue crab and its environment is of public health concern. Therefore, there is a need for frequent antibiotic sensitivity surveillance for Vibrio spp.

Effects of tumbling, refrigeration and subsequent resubmersion on the abundance of Vibrio vulnificus and Vibrio parahaemolyticus in cultured oysters (Crassostrea virginica)

Routine handling of oysters is a common industry practice for off-bottom oyster aquaculture, which aims to produce a high-quality oyster. These practices expose oysters to elevated temperatures and interrupt filter feeding, which can increase Vibrio vulnificus and V. parahaemolyticus levels within the oyster. The resubmersion of oysters after exposure to conditions where the time-temperature controls are exceeded is as an effective mitigation strategy to allow elevated levels of Vibrio spp. to "recover", or return to ambient levels, prior to harvest. Previous work examined the effect of desiccation on recovery times; the objective of this study was to evaluate the effect of additional handling treatments [tumbled and refrigerated (TR), tumbled and not refrigerated (TNR), not tumbled and refrigerated (NTR), and not tumbled and not refrigerated (NTNR)] on the time needed for V. vulnificus, total V. parahaemolyticus, and pathogenic V. parahaemolyticus (tdh+/trh+) to recover in oysters. A set of non-treated (control) oysters remained submerged throughout the study to determine the ambient Vibrio spp. (inclusive of genotypes) levels within oysters. Vibrio spp. levels were measured immediately before (pre) and after (post) the treatments, and 1, 2, 4, 7, 10, and 14 days after resubmersion using a three-tube MPN real-time PCR method. The non-refrigerated oysters (TNR, NTNR) had Vibrio spp. levels 1.54 to 2.10 log MPN/g higher than the pre-treatment levels, while the Vibrio spp. levels in refrigerated oysters were not significantly higher than pre-treatment levels. After resubmersion, Vibrio spp. levels increased by 0.84 to 1.78 log MPN/g in the refrigerated oysters (TR, NTR). Vibrio spp. levels in oysters returned to ambient after 1-7 days of resubmersion, depending on the handling treatment and the Vibrio spp. These results provide data on handling treatments not previously reported and further support the seven-day resubmersion requirement for farmers in Alabama using the adjustable longline system.

Human Health and Ocean Pollution

Background

Pollution - unwanted waste released to air, water, and land by human activity - is the largest environmental cause of disease in the world today. It is responsible for an estimated nine million premature deaths per year, enormous economic losses, erosion of human capital, and degradation of ecosystems. Ocean pollution is an important, but insufficiently recognized and inadequately controlled component of global pollution. It poses serious threats to human health and well-being. The nature and magnitude of these impacts are only beginning to be understood.

Goals

(1) Broadly examine the known and potential impacts of ocean pollution on human health. (2) Inform policy makers, government leaders, international organizations, civil society, and the global public of these threats. (3) Propose priorities for interventions to control and prevent pollution of the seas and safeguard human health.

Methods

Topic-focused reviews that examine the effects of ocean pollution on human health, identify gaps in knowledge, project future trends, and offer evidence-based guidance for effective intervention.

Environmental Findings

Pollution of the oceans is widespread, worsening, and in most countries poorly controlled. It is a complex mixture of toxic metals, plastics, manufactured chemicals, petroleum, urban and industrial wastes, pesticides, fertilizers, pharmaceutical chemicals, agricultural runoff, and sewage. More than 80% arises from land-based sources. It reaches the oceans through rivers, runoff, atmospheric deposition and direct discharges. It is often heaviest near the coasts and most highly concentrated along the coasts of low- and middle-income countries. Plastic is a rapidly increasing and highly visible component of ocean pollution, and an estimated 10 million metric tons of plastic waste enter the seas each year. Mercury is the metal pollutant of greatest concern in the oceans; it is released from two main sources - coal combustion and small-scale gold mining. Global spread of industrialized agriculture with increasing use of chemical fertilizer leads to extension of Harmful Algal Blooms (HABs) to previously unaffected regions. Chemical pollutants are ubiquitous and contaminate seas and marine organisms from the high Arctic to the abyssal depths.

Ecosystem Findings

Ocean pollution has multiple negative impacts on marine ecosystems, and these impacts are exacerbated by global climate change. Petroleum-based pollutants reduce photosynthesis in marine microorganisms that generate oxygen. Increasing absorption of carbon dioxide into the seas causes ocean acidification, which destroys coral reefs, impairs shellfish development, dissolves calcium-containing microorganisms at the base of the marine food web, and increases the toxicity of some pollutants. Plastic pollution threatens marine mammals, fish, and seabirds and accumulates in large mid-ocean gyres. It breaks down into microplastic and nanoplastic particles containing multiple manufactured chemicals that can enter the tissues of marine organisms, including species consumed by humans. Industrial releases, runoff, and sewage increase frequency and severity of HABs, bacterial pollution, and anti-microbial resistance. Pollution and sea surface warming are triggering poleward migration of dangerous pathogens such as the Vibrio species. Industrial discharges, pharmaceutical wastes, pesticides, and sewage contribute to global declines in fish stocks.

Human Health Findings

Methylmercury and PCBs are the ocean pollutants whose human health effects are best understood. Exposures of infants in utero to these pollutants through maternal consumption of contaminated seafood can damage developing brains, reduce IQ and increase children's risks for autism, ADHD and learning disorders. Adult exposures to methylmercury increase risks for cardiovascular disease and dementia. Manufactured chemicals - phthalates, bisphenol A, flame retardants, and perfluorinated chemicals, many of them released into the seas from plastic waste - can disrupt endocrine signaling, reduce male fertility, damage the nervous system, and increase risk of cancer. HABs produce potent toxins that accumulate in fish and shellfish. When ingested, these toxins can cause severe neurological impairment and rapid death. HAB toxins can also become airborne and cause respiratory disease. Pathogenic marine bacteria cause gastrointestinal diseases and deep wound infections. With climate change and increasing pollution, risk is high that Vibrio infections, including cholera, will increase in frequency and extend to new areas. All of the health impacts of ocean pollution fall disproportionately on vulnerable populations in the Global South - environmental injustice on a planetary scale.

Conclusions

Ocean pollution is a global problem. It arises from multiple sources and crosses national boundaries. It is the consequence of reckless, shortsighted, and unsustainable exploitation of the earth's resources. It endangers marine ecosystems. It impedes the production of atmospheric oxygen. Its threats to human health are great and growing, but still incompletely understood. Its economic costs are only beginning to be counted.Ocean pollution can be prevented. Like all forms of pollution, ocean pollution can be controlled by deploying data-driven strategies based on law, policy, technology, and enforcement that target priority pollution sources. Many countries have used these tools to control air and water pollution and are now applying them to ocean pollution. Successes achieved to date demonstrate that broader control is feasible. Heavily polluted harbors have been cleaned, estuaries rejuvenated, and coral reefs restored.Prevention of ocean pollution creates many benefits. It boosts economies, increases tourism, helps restore fisheries, and improves human health and well-being. It advances the Sustainable Development Goals (SDG). These benefits will last for centuries.

Recommendations

World leaders who recognize the gravity of ocean pollution, acknowledge its growing dangers, engage civil society and the global public, and take bold, evidence-based action to stop pollution at source will be critical to preventing ocean pollution and safeguarding human health.Prevention of pollution from land-based sources is key. Eliminating coal combustion and banning all uses of mercury will reduce mercury pollution. Bans on single-use plastic and better management of plastic waste reduce plastic pollution. Bans on persistent organic pollutants (POPs) have reduced pollution by PCBs and DDT. Control of industrial discharges, treatment of sewage, and reduced applications of fertilizers have mitigated coastal pollution and are reducing frequency of HABs. National, regional and international marine pollution control programs that are adequately funded and backed by strong enforcement have been shown to be effective. Robust monitoring is essential to track progress.Further interventions that hold great promise include wide-scale transition to renewable fuels; transition to a circular economy that creates little waste and focuses on equity rather than on endless growth; embracing the principles of green chemistry; and building scientific capacity in all countries.Designation of Marine Protected Areas (MPAs) will safeguard critical ecosystems, protect vulnerable fish stocks, and enhance human health and well-being. Creation of MPAs is an important manifestation of national and international commitment to protecting the health of the seas.

Effect of Ploidy on Vibrio parahaemolyticus and Vibrio vulnificus Levels in Cultured Oysters

Vibrio parahaemolyticus and V. vulnificus are naturally occuring human pathogenic bacteria commonly found in estuarine environments where oysters are cultured. The use of triploid oysters has increased, due to their rapid growth rate and that they maintain a high quality throughout the year. Previous work suggested levels of Vibrio spp. may be lower in triploid oysters, as compared to diploids. Therfore, this study aimed to determine if there is a difference in the abundances of V. parahaemolyticus and V. vulnificus between half-sibling diploid and triploid oysters. In four trials, 100 individual oysters (either iced or temperature abused) were analyzed for V. parahaemolyticus and V. vulnificus using direct plating followed by colony hybridization. Mean levels of V. parahaemolyticus in iced and abused diploid oysters were 3.55 and 4.21 log CFU/g, respectively. Mean levels in iced and abused triploid oysters were 3.49 and 4.27 log CFU/g, respectively. Mean levels of V. vulnificus in iced and abused diploid oysters were 3.53 and 4.56 log CFU/g, respectively. Mean levels in iced and abused triploid oysters were 3.54 and 4.55 log CFU/g, respectively. The differences in Vibrio spp. abundances between diploid and triploid oysters was not significant (p>0.05). However, the differences across treatments were significant (p<0.05), with the exception of V. parahaemolyticus levels in trial 3 (p=0.83). Variation between individual oysters was also observed, with 12 of 808 measurements being outside of the 95 th percentile. This phenomenon of occasional statistical outliers ("hot" or "cold" oysters) has been previously described and supports the appropriateness of composite sampling to account for inherent animal variability. In summary, the data indicate that abundances of V. parahaemolyticus and V. vulnificus are not dependent on the ploidy of cultured oysters, but vary with the type of handling.

Structure, Function, and Regulation of the Essential Virulence Factor Capsular Polysaccharide of Vibrio vulnificus

Vibrio vulnificus populates coastal waters around the world, where it exists freely or becomes concentrated in filter feeding mollusks. It also causes rapid and life-threatening sepsis and wound infections in humans. Of its many virulence factors, it is the V. vulnificus capsule, composed of capsular polysaccharide (CPS), that plays a critical role in evasion of the host innate immune system by conferring antiphagocytic ability and resistance to complement-mediated killing. CPS may also provoke a portion of the host inflammatory cytokine response to this bacterium. CPS production is biochemically and genetically diverse among strains of V. vulnificus, and the carbohydrate diversity of CPS is likely affected by horizontal gene transfer events that result in new combinations of biosynthetic genes. Phase variation between virulent encapsulated opaque colonial variants and attenuated translucent colonial variants, which have little or no CPS, is a common phenotype among strains of this species. One mechanism for generating acapsular variants likely involves homologous recombination between repeat sequences flanking the wzb phosphatase gene within the Group 1 CPS biosynthetic and transport operon. A considerable number of environmental, genetic, and regulatory factors have now been identified that affect CPS gene expression and CPS production in this pathogen.

A comparison between farmed oysters using floating cages and oysters grown on-bottom reveals more potentially human pathogenic Vibrio in the on-bottom oysters

Eating raw oysters can come with serious health risks, as oysters can potentially contain bacteria of the Vibrio genus that cause food-borne infections. Vibrio bacteria are concentrated by oysters and, when consumed, infections can result with severe symptoms such as diarrhoea, lesions on the extremities, or even death. Vibrio spp. concentrations are strongly affected by season, location, and other factors such as temperature and salinity. Previous research in North Carolina oysters has been conducted on wild and farmed oysters but not at the same time. Farmed, or aquaculture raised, oysters are considerably different from wild oysters and could possibly pose different health risks. Farmed oysters are handled, raised from seed, and often grown using suspended grow-out systems called 'floating cages'. Therefore, farmed oysters can be grown at the surface of the estuary, while wild oysters typically grow at the bottom of the water column. This project compared the concentrations of Vibrio spp. in suspended, farm-grown oysters and wild oysters at three sites, using a paired approach with farmed and wild oysters sampled in proximity. An important part of this comparison was identifying pathogenicity of the bacteria isolated from the samples. Distinction was made between off- and on-bottom farming. Interestingly, on-bottom oysters had more pathogenic V. vulnificus than off-bottom oysters.

Vibrio vulnificus cytolysin induces inflammatory responses in RAW264.7 macrophages through calcium signaling and causes inflammation in vivo

Vibrio vulnificus is a food-borne marine pathogen that causes both life-threatening primary septicemia and necrotizing wound infections which accompany severe inflammation. Cytolysin is a very powerful virulence factor of V. vulnificus and is one of the likely candidates in the pathogenesis of V. vulnificus infections. However, the pathogenetic roles of cytolysin in V. vulnificus-induced inflammation are not well understood. In this study, we used the recombinant protein Vibrio vulnificus cytolysin (VVC) to demonstrate that VVC can induce inflammatory responses in RAW264.7 macrophages. Low dose (<5 μg/ml) VVC had no impact on cell viability and induced pro-inflammatory cytokines production in RAW264.7 macrophages such as IL-6 and TNF-α. Moreover, VVC induced p65, p38, ERK1/2, and AKT phosphorylation in RAW264.7 macrophages. We further demonstrated that BAPTA-AM, a specific intracellular calcium chelator, inhibited VVC-induced inflammatory responses including pro-inflammatory cytokines production and inflammatory signaling activation in RAW264.7 macrophages. In addition, VVC primed rather than actived NLRP3 inflammasome in RAW264.7 macrophages. To determine whether VVC have a direct inflammatory effect on the host, we examined the effects of VVC injected into the skin of mice. VVC stimulated a significant induction of mRNAs for the pro-inflammatory cytokine IL-6 and inflammatory chemokines such as MCP-1 and IP-10. Histology data also showed that VVC caused inflammatory responses in the skin of mice. Collectively, our findings indicated that VVC induced inflammatory responses in RAW264.7 macrophages and in vivo and suggested the possibility of targeting VVC as a strategy for the clinical management of V. vulnificus-induced inflammatory responses.

Whole-genome comparison between reference sequences and oyster Vibrio vulnificus C-genotype strains

Whole-genome sequences of Vibrio vulnificus clinical genotype (C-genotype) from the CICESE Culture Collection, isolated from oysters, were compared with reference sequences of CMCP6 and YJ016 V. vulnificus C-genotype strains of clinical origin. The RAST web server estimated the whole genome to be ~4.8 Mb in CICESE strain 316 and ~4.7 Mb in CICESE strain 325. No plasmids were detected in the CICESE strains. Based on a phylogenetic tree that was constructed with the whole-genome results, we observed high similarity between the reference sequences and oyster C-genotype isolates and a sharp contrast with environmental genotype (E-genotype) reference sequences, indicating that the differences between the C- and E-genotypes do not necessarily correspond to their isolation origin. The CICESE strains share 3488 genes (63.2%) with the YJ016 strain and 3500 genes (63.9%) with the CMCP6 strain. A total of 237 pathogenicity associated genes were selected from reference clinical strains, where—92 genes were from CMCP6, 126 genes from YJ016, and 19 from MO6-24/O; the presence or absence of these genes was recorded for the CICESE strains. Of the 92 genes that were selected for CMCP6, 67 were present in both CICESE strains, as were as 86 of the 126 YJ016 genes and 13 of the 19 MO6-24/O genes. The detection of elements that are related to virulence in CICESE strains—such as the RTX gene cluster, vvhA and vvpE, the type IV pili cluster, the XII genomic island, and the viuB genes, suggests that environmental isolates with the C-genotype, have significant potential for infection.

Unveiling the acid stress response of clinical genotype Vibrio vulnificus isolated from the marine environments of Mangaluru coast, India

Gastric acidity is one of the earliest host defences faced by ingested organisms, and successful pathogens need to overcome this hurdle. The objective of this study was the systematic assessment of acid-stress response of Vibrio vulnificus isolated from coastal regions of Mangaluru. Acid-shock experiments were carried out at pH 4.0 and pH 4.5, with different experimental conditions expected to produce a varied acid response. Exposure to mild acid before the acid shock was favourable to the bacteria but was dependent on cell population and pH of the media and was independent of the strains tested. Lysine-dependent acid response was demonstrated with reference to the previously identified lysine decarboxylase system. Additionally, the results showed that inoculation into oysters provided some level of protection against acid stress. Increased expression of lysine/cadaverine genes was observed upon the addition of ground oyster and was confirmed by quantitative real-time PCR. The potential role of ornithine was analyzed with regard to acid stress, but no change in the survival pattern was observed. These findings highlight the physiology of bacteria in acid stress.

Late-onset Vibrio vulnificus septicemia without cirrhosis

Recent surveillance from the Centers for Disease Control and Prevention indicates rising annual incidence rates of Vibrio vulnificus infection. Unfortunately, this infection is often excluded from the differential diagnosis in lesser known at-risk populations. Transmission occurs via wound exposure or ingestion, with V. vulnificus foodborne illness having the highest mortality rate of all Vibrio species. Fatality rates of V. vulnificus rival those of Ebola and bubonic plague, so timely treatment is imperative. Current literature favors surgical debridement with a third-generation cephalosporin plus intravenous doxycycline or fluoroquinolone. Cephalosporin monotherapy is discouraged due to rising resistance. This case features V. vulnificus septicemia with prolonged incubation time in a noncirrhotic patient.

Evolutionary Model of Cluster Divergence of the Emergent Marine Pathogen Vibrio vulnificus: From Genotype to Ecotype

Vibrio vulnificus is an emergent marine pathogen and is the cause of a deadly septicemia. However, the genetic factors that differentiate its clinical and environmental strains and its several biotypes remain mostly enigmatic. In this work, we investigated the underlying genomic properties and population dynamics of the V. vulnificus species to elucidate the traits that make these strains emerge as a human pathogen. The acquisition of different ecological determinants could have allowed the development of highly divergent clusters with different lifestyles within the same environment. However, we identified strains from both clusters in the mucosa of aquaculture species, indicating that manmade niches are bringing strains from the two clusters together, posing a potential risk of recombination and of emergence of novel variants. We propose a new evolutionary model that provides a perspective that could be broadly applicable to other pathogenic vibrios and facultative bacterial pathogens to pursue strategies to prevent their infections.

Vibrio vulnificus, an opportunistic pathogen, is the causative agent of a life-threatening septicemia and a rising problem for aquaculture worldwide. The genetic factors that differentiate its clinical and environmental strains remain enigmatic. Furthermore, clinical strains have emerged from every clade of V. vulnificus. In this work, we investigated the underlying genomic properties and population dynamics of the V. vulnificus species from an evolutionary and ecological point of view. Genome comparisons and bioinformatic analyses of 113 V. vulnificus isolates indicate that the population of V. vulnificus is made up of four different clusters. We found evidence that recombination and gene flow between the two largest clusters (cluster 1 [C1] and C2) have drastically decreased to the point where they are diverging independently. Pangenome and phenotypic analyses showed two markedly different lifestyles for these two clusters, indicating commensal (C2) and bloomer (C1) ecotypes, with differences in carbohydrate utilization, defense systems, and chemotaxis, among other characteristics. Nonetheless, we identified frequent intra- and interspecies exchange of mobile genetic elements (e.g., antibiotic resistance plasmids, novel “chromids,” or two different and concurrent type VI secretion systems) that provide high levels of genetic diversity in the population. Surprisingly, we identified strains from both clusters in the mucosa of aquaculture species, indicating that manmade niches are bringing strains from the two clusters together. We propose an evolutionary model of V. vulnificus that could be broadly applicable to other pathogenic vibrios and facultative bacterial pathogens to pursue strategies to prevent their infections and emergence.

Temporal and Environmental Factors Driving Vibrio Vulnificus and V. Parahaemolyticus Populations and Their Associations With Harmful Algal Blooms in South Carolina Detention Ponds and Receiving Tidal Creeks

Incidences of harmful algal blooms (HABs) and Vibrio infections have increased over recent decades. Numerous studies have tried to identify environmental factors driving HABs and pathogenic Vibrio populations separately. Few have considered the two simultaneously, though emerging evidence suggests that algal blooms enhance Vibrio growth and survival. This study examined various physical, nutrient, and temporal factors associated with incidences of HABs, V. vulnificus, and V. parahaemolyticus in South Carolina coastal stormwater detention ponds, managed systems where HABs often proliferate, and their receiving tidal creek waters. Five blooms occurred during the study (2008-2009): two during relatively warmer months (an August 2008 cyanobacteria bloom and a November 2008 dinoflagellate bloom) followed by increases in both Vibrio species and V. parahaemolyticus, respectively, and three during cooler months (December 2008 through February 2009) caused by dinoflagellates and euglenophytes that were not associated with marked changes in Vibrio abundances. Vibrio concentrations were positively and significantly associated with temperature and dissolved organic matter, dinoflagellate blooms, negatively and significantly associated with suspended solids, but not significantly correlated with chlorophyll or nitrogen. While more research involving longer time series is needed to increase robustness, findings herein suggest that certain HAB species may augment Vibrio occurrences during warmer months.

Effects of Desiccation Practices of Cultured Atlantic Oysters (Crassostrea virginica) on Vibrio spp. in Portersville Bay, Alabama, USA

The expansion of off-bottom aquaculture to the Gulf of Mexico has raised public health concerns for human health officials. High temperatures in the Gulf of Mexico are associated with high levels of Vibrio parahaemolyticus and Vibrio vulnificus. Routine desiccation practices associated with off-bottom aquaculture expose oysters to ambient air, allowing Vibrio spp. to proliferate in the closed oyster. Currently, there is limited research on the length of time needed for Vibrio spp. levels in desiccated oysters to return to background levels, defined as the levels found in oysters that remain continually submersed and not exposed to ambient air. This study determined the time needed to return V. parahaemolyticus, V. vulnificus, and Vibrio cholerae levels to background levels in oysters exposed to the following desiccation practices: 3-h freshwater dip followed by 24-h ambient air exposure, 27-h ambient air exposure, and control. All oysters were submerged at least 2 weeks prior to the beginning of each trial, with the control samples remaining submerged for the duration of each trial. Vibrio spp. levels were enumerated from samples collected on days 0, 1, 2, 3, 7, 10, and 14 after resubmersion using a three-tube most-probable-number enrichment followed by BAX PCR. V. cholerae levels were frequently (92%) below the limit of detection at all times, so they were not statistically analyzed. V. parahaemolyticus and V. vulnificus levels in the 27-h ambient air exposure and the 3-h freshwater dip followed by 24-h ambient air exposure samples were significantly elevated compared with background samples. In most cases, the Vibrio spp. levels in oysters in both desiccation treatments remained elevated compared with background levels until 2 or 3 days post-resubmersion. However, there was one trial in which the Vibrio spp. levels did not return to background levels until day 7. The results of this study provide scientific support that oyster farmers should be required to implement a minimum 7-day resubmersion regimen. This length of time allowed the Vibrio spp. levels to become not significantly different across all treatments.

Vibrio vulnificus: An Environmental and Clinical Burden

Vibrio vulnificus is a Gram negative, rod shaped bacterium that belongs to the family Vibrionaceae. It is a deadly, opportunistic human pathogen which is responsible for the majority of seafood-associated deaths worldwide. V. vulnificus infection can be fatal as it may cause severe wound infections potentially requiring amputation or lead to sepsis in susceptible individuals. Treatment is increasingly challenging as V. vulnificus has begun to develop resistance against certain antibiotics due to their indiscriminate use. This article aims to provide insight into the antibiotic resistance of V. vulnificus in different parts of the world as well as an overall review of its clinical manifestations, treatment, and prevention. Understanding the organism's antibiotic resistance profile is vital in order to select appropriate treatment and initiate appropriate prevention measures to treat and control V. vulnificus infections, which should eventually help lower the mortality rate associated with this pathogen worldwide.

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.

Impact of hypoxia on gene expression patterns by the human pathogen, Vibrio vulnificus, and bacterial community composition in a North Carolina estuary

Estuarine environments are continuously being shaped by both natural and anthropogenic sources which directly/indirectly influence the organisms that inhabit these important niches on both individual and community levels. Human infections caused by pathogenic Vibrio species are continuing to rise, and factors associated with global climate change have been suggested to be impacting their abundance and geographical range. Along with temperature, hypoxia has also increased dramatically in the last 40 years, which has led to persistent dead zones worldwide in areas where these infections are increasing. Thus, utilizing membrane diffusion chambers, we investigated the impact of in situ hypoxia on the gene expression of one such bacterium, Vibrio vulnificus, which is an inhabitant of these vulnerable areas worldwide. By coupling these data with multiple abiotic factors, we were able to demonstrate that genes involved in numerous functions, including those involved in virulence, environmental persistence, and stressosome production, were negatively correlated with dissolved oxygen. Furthermore, comparing 16S ribosomal RNA, we found similar overall community compositions during both hypoxia and normoxia. However, unweighted beta diversity analyses revealed that although certain classes of bacteria dominate in both low- and high-oxygen environments, there is the potential for quantitative shifts in lower abundant species, which may be important for effective risk assessment in areas that are becoming increasingly more hypoxic. This study emphasizes the importance of investigating hypoxia as a trigger for gene expression changes by marine Vibrio species and highlights the need for more in depth community analyses during estuarine hypoxia.

Effects of Pyrogallol on Growth and Cytotoxicity of Wild-Type and katG Mutant Strains of Vibrio vulnificus

Vibrio vulnificus is a causative agent of fatal septicemia and necrotic wound infection and the pathogen infection became an important public health problem in many counties. Vibrio vulnificus causes RtxA1 toxin-induced acute cell death. We tried to identify natural products that inhibit the acute cytotoxicity of V. vulnificus using a lactate hydrogenase assay. A polyphenol pyrogallol protected HeLa cells from V. vulnificus-induced cytotoxicity. Pyrogallol also decreased the growth of V. vulnificus; this inhibitory effect was more significant during log phase than stationary phase. To further elucidate the inhibitory mechanism, pyrogallol-induced toxicity was compared between a V. vulnificus catalase-peroxidase mutant (katG⁻) and the isogenic wild-type MO6-24/O strains. No growth was observed for the katG⁻ mutant in the presence of pyrogallol (50 μg/mL) even after 24 h, whereas the wild-type strain demonstrated growth recovery following a prolonged lag phase. Pyrogallol-mediated growth inhibition of the katG⁻ mutant strain was partially rescued by exogenous catalase treatment. These results indicate that the mechanism by which pyrogallol inhibits the growth and cytotoxicity of V. vulnificus likely involves polyphenol-induced prooxidant damage. Taken together, these results suggest that pyrogallol has potential for development as a new paradigm drug to treat infectious diseases.

Faraday cage-type electrochemiluminescence immunosensor for ultrasensitive detection of Vibrio vulnificus based on multi-functionalized graphene oxide

A novel Faraday cage-type electrochemiluminescence (ECL) immunosensor devoted to the detection of Vibrio vulnificus (VV) was fabricated. The sensing strategy was presented by a unique Faraday cage-type immunocomplex based on immunomagnetic beads (IMBs) and multi-functionalized graphene oxide (GO) labeled with (2,2'-bipyridine)(5-aminophenanthroline)ruthenium (Ru-NH2). The multi-functionalized GO could sit on the electrode surface directly due to the large surface area, abundant functional groups, and good electronic transport property. It ensures that more Ru-NH2 is entirely caged and become "effective," thus improving sensitivity significantly, which resembles extending the outer Helmholtz plane (OHP) of the electrode. Under optimal conditions, the developed immunosensor achieves a limit of detection as low as 1 CFU/mL. Additionally, the proposed immunosensor with high sensitivity and selectivity can be used for the detection of real samples. The novel Faraday cage-type method has shown potential application for the diagnosis of VV and opens up a new avenue in ECL immunoassay. Graphical abstract Faraday cage-type immunoassay mode for ultrasensitive detection by extending OHP.

Effects of Intertidal Harvest Practices on Levels of Vibrio parahaemolyticus and Vibrio vulnificus Bacteria in Oysters

Vibrio parahaemolyticus and Vibrio vulnificus can grow rapidly in shellfish subjected to ambient air conditions, such as during intertidal exposure. In this study, levels of total and pathogenic (tdh(+) and/or trh(+)) V. parahaemolyticus and total V. vulnificus were determined in oysters collected from two study locations where intertidal harvest practices are common. Samples were collected directly off intertidal flats, after exposure (ambient air [Washington State] or refrigerated [New Jersey]), and after reimmersion by natural tidal cycles. Samples were processed using a most-probable-number (MPN) real-time PCR method for total and pathogenic V. parahaemolyticus or V. vulnificus In Washington State, the mean levels of V. parahaemolyticus increased 1.38 log MPN/g following intertidal exposure and dropped 1.41 log MPN/g after reimmersion for 1 day, but the levels were dependent upon the container type utilized. Pathogenic V. parahaemolyticus levels followed a similar trend. However, V. vulnificus levels increased 0.10 log MPN/g during intertidal exposure in Washington but decreased by >1 log MPN/g after reimmersion. In New Jersey, initial levels of all vibrios studied were not significantly altered during the refrigerated sorting and containerizing process. However, there was an increase in levels after the first day of reimmersion by 0.79, 0.72, 0.92, and 0.71 log MPN/g for total, tdh(+) and trh(+) V. parahaemolyticus, and V. vulnificus, respectively. The levels of all targets decreased to those similar to background after a second day of reimmersion. These data indicate that the intertidal harvest and handling practices for oysters that were studied in Washington and New Jersey do not increase the risk of illness from V. parahaemolyticus or V. vulnificus

IMPORTANCE

Vibrio parahaemolyticus and Vibrio vulnificus are the leading causes of seafood-associated infectious morbidity and mortality in the United States. Vibrio spp. can grow rapidly in shellfish subjected to ambient air conditions, such as during periods of intertidal exposure. When oysters are submersed with the incoming tide, the vibrios can be purged. However, data on the rates of increase and purging during intertidal harvest are scarce, which limits the accuracy of risk assessments. The objective of this study was to help fill these data gaps by determining the levels of total and pathogenic (tdh(+) and/or trh(+)) V. parahaemolyticus and V. vulnificus in oysters from two locations where intertidal harvest practices are common, using the current industry practices. The data generated provide insight into the responses of Vibrio spp. to relevant practices of the industry and public health, which can be incorporated into risk management decisions.

Differential Expression of Inflammatory Cytokines and Stress Genes in Male and Female Mice in Response to a Lipopolysaccharide Challenge

BACKGROUND

Sex plays a key role in an individual's immune response against pathogenic challenges such that females fare better when infected with certain pathogens. It is thought that sex hormones impact gene expression in immune cells and lead to sexually dimorphic responses to pathogens. We predicted that, in the presence of E. coli gram-negative lipopolysaccharide (LPS), there would be a sexually dimorphic response in proinflammatory cytokine production and acute phase stress gene expression and that these responses might vary among different mouse strains and times in a pattern opposite to that of body temperature associated with LPS-induced shock.

MATERIALS AND METHODS

Interleukin-6 (IL-6), macrophage inflammatory protein-Iβ (MIP-1β), tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) as well as beta-fibrinogen (Fgb) and metallothionein-1 (Mt-1) mRNA expression were measured at four time points (0, 2, 4 and 7 hours) after injection of E. coli LPS in mice from three inbred strains.

RESULTS

Statistical analysis using analyses of variance (ANOVAs) showed that the levels of the all six traits changed over time, generally peaking at 2 hours after LPS injection. Mt-1, Fgb, and IL-6 showed differences among strains, although these were time-specific. Sexual dimorphism was seen for Fgb and IL6, and was most pronounced at the latest time period (7 hours) where male levels exceeded those for females. Trends for all six cytokine/gene expression traits were negatively correlated with those for body temperatures.

DISCUSSION

The higher levels of expression of Fgb and IL6 in males compared with females are consistent with the greater vulnerability of males to infection and subsequent inflammation. Temperature appears to be a useful proxy for mortality in endotoxic shock, but sexual dimorphism in cytokine and stress gene expression levels may persist after an LPS challenge even if temperatures in the two sexes are similar and have begun to stabilize.

The Biology of Vibrio vulnificus

Vibrio vulnificus, carrying a 50% fatality rate, is the most deadly of the foodborne pathogens. It occurs in estuarine and coastal waters and it is found in especially high numbers in oysters and other molluscan shellfish. The biology of V. vulnificus, including its ecology, pathogenesis, and molecular genetics, has been described in numerous reviews. This article provides a brief summary of some of the key aspects of this important human pathogen, including information on biotypes and genotypes, virulence factors, risk factor requirements and the role of iron in disease, association with oysters, geographic distribution, importance of salinity and water temperature, increasing incidence associated with global warming. This article includes some of our findings as presented at the "Vibrios in the Environment 2010" conference held in Biloxi, MS.

Occurrence and molecular characterisation of Vibrio parahaemolyticus in crustaceans commercialised in Venice area, Italy

Infections due to the pathogenic human vibrios, Vibrio parahaemolyticus, Vibrio cholerae and Vibrio vulnificus, are mainly associated with consumption of raw or partially cooked bivalve molluscs. At present, little is known about the presence of Vibrio species in crustaceans and the risk of vibriosis associated with the consumption of these products. The aim of the present study was to evaluate the prevalence and concentration of the main pathogenic Vibrio spp. in samples of crustaceans (n=143) commonly eaten in Italy, taking into account the effects of different variables such as crustacean species, storage conditions and geographic origin. Subsequently, the potential pathogenicity of V. parahaemolyticus strains isolated from crustaceans (n=88) was investigated, considering the classic virulence factors (tdh and trh genes) and four genes coding for relevant proteins of the type III secretion systems 2 (T3SS2α and T3SS2β). In this study, the presence of V. cholerae and V. vulnificus was never detected, whereas 40 samples (28%) were positive for V. parahaemolyticus with an overall prevalence of 41% in refrigerated products and 8% in frozen products. The highest prevalence and average contamination levels were detected in Crangon crangon (prevalence 58% and median value 3400 MPN/g) and in products from the northern Adriatic Sea (35%), with the samples from the northern Venetian Lagoon reaching a median value of 1375 MPN/g. While genetic analysis confirmed absence of the tdh gene, three of the isolates contained the trh gene and, simultaneously, the T3SS2β genes. Moreover three possibly clonal tdh-negative/trh-negative isolates carried the T3SS2α apparatus. The detection of both T3SS2α and T3SS2β apparatuses in V. parahaemolyticus strains isolated from crustaceans emphasised the importance of considering new genetic markers associated with virulence besides the classical factors. Moreover this study represents the first report dealing with Vibrio spp. in crustaceans in Italy, and it may provide useful information for the development of sanitary surveillance plans to prevent the risk of vibriosis in seafood consumers.

Manganese is an additional cation that enhances colonial phase variation of Vibrio vulnificus

Vibrio vulnificus, an inhabitant of marine and estuarine environments around the world, is the leading cause of reported seafood-related deaths in the United States. Disease is caused by opaque colony-forming strains that produce capsular polysaccharide, loss of which results in an unencapsulated translucent phenotype with diminished virulence potential. Rugose is a third phenotypic variant of V. vulnificus, and produces a separate exopolysaccharide that results in a dry, wrinkled appearance and the ability to form profuse biofilms. Phase variation among these three phenotypes is influenced by several environmental factors, including the presence of calcium in the medium (Garrison-Schilling et al.). In this study, we have identified a second cation, manganese, which substantially increases the propensity of opaque V. vulnificus strains to switch to translucent or rugose phenotypes. In comparative studies, manganese and calcium promoted switching to the same phenotype for some strains but to different phenotypes for others, results of which indicate that the two cations do not always promote the same changes in underlying gene expression. The data here provide further evidence that exposure of V. vulnificus to select cations results in phenotypic changes that impact both virulence capacity and ecology of the organism.

Clinical and environmental genotypes of Vibrio vulnificus display distinct, quorum-sensing-mediated, chitin detachment dynamics

The ability for bacteria to attach to and detach from various substrata is important for colonization, survival and transitioning to new environments. An opportunistic human pathogen, Vibrio vulnificus, can cause potentially fatal septicemia after ingestion of undercooked seafood. Based on genetic polymorphisms, strains of this species are subtyped into clinical (C) and environmental (E) genotypes. Vibrio vulnificus readily associates with chitin, thus we investigated chitin detachment dynamics in these disparate genotypes. We found that C-genotypes detach significantly more than E-genotypes after 24 hours in aerobic as well as anaerobic conditions. Furthermore, expression of genes involved in type IV pilin production was significantly downregulated in C-genotypes compared to E-genotypes, suggesting an importance in detachment. Interestingly, gbpA, a gene that has been shown to be important in host colonization in V. cholerae, was upregulated in the C-genotypes during detachment. Additionally, we found that C-genotypes detached to a greater extent, and produced more quorum-sensing (QS) autoinducer-2 molecules relative to E-genotypes, which suggests a role for QS in detachment. These findings suggest that for V. vulnificus, QS-mediated detachment may be a potential mechanism for transitioning into a human host for C-genotypes, while facilitating E-genotype maintenance in the estuarine environment.

Functional Analyses of Resurrected and Contemporary Enzymes Illuminate an Evolutionary Path for the Emergence of Exolysis in Polysaccharide Lyase Family 2

Family 2 polysaccharide lyases (PL2s) preferentially catalyze the β-elimination of homogalacturonan using transition metals as catalytic cofactors. PL2 is divided into two subfamilies that have been generally associated with secretion, Mg(2+) dependence, and endolysis (subfamily 1) and with intracellular localization, Mn(2+) dependence, and exolysis (subfamily 2). When present within a genome, PL2 genes are typically found as tandem copies, which suggests that they provide complementary activities at different stages along a catabolic cascade. This relationship most likely evolved by gene duplication and functional divergence (i.e. neofunctionalization). Although the molecular basis of subfamily 1 endolytic activity is understood, the adaptations within the active site of subfamily 2 enzymes that contribute to exolysis have not been determined. In order to investigate this relationship, we have conducted a comparative enzymatic analysis of enzymes dispersed within the PL2 phylogenetic tree and elucidated the structure of VvPL2 from Vibrio vulnificus YJ016, which represents a transitional member between subfamiles 1 and 2. In addition, we have used ancestral sequence reconstruction to functionally investigate the segregated evolutionary history of PL2 progenitor enzymes and illuminate the molecular evolution of exolysis. This study highlights that ancestral sequence reconstruction in combination with the comparative analysis of contemporary and resurrected enzymes holds promise for elucidating the origins and activities of other carbohydrate active enzyme families and the biological significance of cryptic metabolic pathways, such as pectinolysis within the zoonotic marine pathogen V. vulnificus.

Molecular and Physical Factors That Influence Attachment of Vibrio vulnificus to Chitin

The human pathogen Vibrio vulnificus is the leading cause of seafood-related deaths in the United States. Strains are genotyped on the basis of alleles that correlate with isolation source, with clinical (C)-genotype strains being more often implicated in disease and environmental (E)-genotype strains being more frequently isolated from oysters and estuarine waters. Previously, we have shown that the ecologically distinct C- and E-genotype strains of V. vulnificus display different degrees of chitin attachment, with C-genotype strains exhibiting reduced attachment relative to their E-genotype strain counterparts. We identified type IV pili to be part of the molecular basis for this observed genotypic variance, as E-genotype strains exhibit higher levels of expression of these genes than C-genotype strains. Here, we used a C-genotype quorum-sensing (QS) mutant to demonstrate that quorum sensing is a negative regulator of type IV pilus expression, which results in decreased chitin attachment. Furthermore, calcium depletion reduced E-genotype strain attachment to chitin, which suggests that calcium is necessary for proper functioning of the type IV pili in E-genotype strains. We also found that starvation or dormancy can alter the efficiency of chitin attachment, which has significant implications for the environmental persistence of V. vulnificus. With the increasing incidence of wound infections caused by V. vulnificus, we investigated a subset of E-genotype strains isolated from human wound infections and discovered that they attached to chitin in a manner more similar to that of C-genotype strains. This study enhances our understanding of the molecular and physical factors that mediate chitin attachment in V. vulnificus, providing insight into the mechanisms that facilitate the persistence of this pathogen in its native environment.

Development of a matrix tool for the prediction of Vibrio species in oysters harvested from North Carolina

The United States has federal regulations in place to reduce the risk of seafood-related infection caused by the estuarine bacteria Vibrio vulnificus and Vibrio parahaemolyticus. However, data to support the development of regulations have been generated in a very few specific regions of the nation. More regionally specific data are needed to further understand the dynamics of human infection relating to shellfish-harvesting conditions in other areas. In this study, oysters and water were collected from four oyster harvest sites in North Carolina over an 11-month period. Samples were analyzed for the abundances of total Vibrio spp., V. vulnificus, and V. parahaemolyticus; environmental parameters, including salinity, water temperature, wind velocity, and precipitation, were also measured simultaneously. By utilizing these data, preliminary predictive management tools for estimating the abundance of V. vulnificus bacteria in shellfish were developed. This work highlights the need for further research to elucidate the full suite of factors that drive V. parahaemolyticus abundance.

Role of anaerobiosis in capsule production and biofilm formation in Vibrio vulnificus

Vibrio vulnificus, a pervasive human pathogen, can cause potentially fatal septicemia after consumption of undercooked seafood. Biotype 1 strains of V. vulnificus are most commonly associated with human infection and are separated into two genotypes, clinical (C) and environmental (E), based on the virulence-correlated gene. For ingestion-based vibriosis to occur, this bacterium must be able to withstand multiple conditions as it traverses the gastrointestinal tract and ultimately gains entry into the bloodstream. One such condition, anoxia, has yet to be extensively researched in V. vulnificus. We investigated the effect of oxygen availability on capsular polysaccharide (CPS) production and biofilm formation in this bacterium, both of which are thought to be important for disease progression. We found that lack of oxygen elicits a reduction in both CPS and biofilm formation in both genotypes. This is further supported by the finding that pilA, pilD, and mshA genes, all of which encode type IV pilin proteins that aid in attachment to surfaces, were downregulated during anaerobiosis. Surprisingly, E-genotypes exhibited distinct differences in gene expression levels of capsule and attachment genes compared to C-genotypes, both aerobically and anaerobically. The importance of understanding these disparities may give insight into the observed differences in environmental occurrence and virulence potential between these two genotypes of V. vulnificus.

Serum Survival of Vibrio vulnificus: Role of Genotype, Capsule, Complement, Clinical Origin, and in Situ Incubation

Virulence of the human pathogen, V. vulnificus, is associated with encapsulation, serum complement resistance, and genotype. The C-genotype of this bacterium is correlated (>90%) with virulence and with isolation source (clinical settings). E-genotype strains are highly correlated with environmental isolation (93%) but appear less virulent. In this study, we characterized the importance of genotype, encapsulation, serum complement, and in situ exposure to estuarine water on the survival of the two genotypes in human serum. Results confirmed the superior ability of C-genotype strains to survive exposure to human serum, as well as the significance of complement, and revealed that lack of capsule allowed serum killing of both C- and E-genotypes. Cells incubated in situ responded similarly to cells incubated in vitro with the exception of E-environmental strains. Interestingly, our studies found that those cells of the E-genotype, typically considered non-pathogenic, which were isolated from wound infections demonstrated serum survival similar to that of virulent, C-genotype, strains.

Complete Nucleotide Sequence of pVv01, a P1-Like Plasmid Prophage of Vibrio vulnificus

We report here the 79,263-bp plasmid pVv01 isolated from Vibrio vulnificus. pVv01 is closely related to the Vibrio plasmid p0908 and shows some similarities to phage P1. Unlike p0908, pVv01 represents an intact prophage inducible by mitomycin C. PVv01 phage particles revealed a myoviridal morphology and lytic activity.

Vibrio vulnificus phage PV94 is closely related to temperate phages of V. cholerae and other Vibrio species

Background

Vibrio vulnificus is an important pathogen which can cause serious infections in humans. Yet, there is limited knowledge on its virulence factors and the question whether temperate phages might be involved in pathogenicity, as is the case with V. cholerae. Thus far, only two phages (SSP002 and VvAW1) infecting V. vulnificus have been genetically characterized. These phages were isolated from the environment and are not related to Vibrio cholerae phages. The lack of information on temperate V. vulnificus phages prompted us to isolate those phages from lysogenic strains and to compare them with phages of other Vibrio species.

Results

In this study the temperate phage PV94 was isolated from a V. vulnificus biotype 1 strain by mitomycin C induction. PV94 is a myovirus whose genome is a linear double-stranded DNA of 33,828 bp with 5′-protruding ends. Sequence analysis of PV94 revealed a modular organization of the genome. The left half of the genome comprising the immunity region and genes for the integrase, terminase and replication proteins shows similarites to V. cholerae kappa phages whereas the right half containing genes for structural proteins is closely related to a prophage residing in V. furnissii NCTC 11218.

Conclusion

We present the first genomic sequence of a temperate phage isolated from a human V. vulnificus isolate. The sequence analysis of the PV94 genome demonstrates the wide distribution of closely related prophages in various Vibrio species. Moreover, the mosaicism of the PV94 genome indicates a high degree of horizontal genetic exchange within the genus Vibrio, by which V. vulnificus might acquire virulence-associated genes from other species.