Vibrio parahaemolyticus diarrhea, Chile, 1998 and 2004

Serodiversity, antibiotic resistance, and virulence genes of Vibrio parahaemolyticus in oysters collected in coastal areas of northwestern Mexico between 2012 and 2020

This study aimed to determine the prevalence of V. parahaemolyticus in oysters from the northwestern coast of Mexico and to identify the serotypes, virulence factors, and antibiotic resistance of the strains. Oyster samples were collected from 2012 to 2020 from the northwest coast of Mexico; biochemical and molecular methods were used to identify V. parahaemolyticus from oysters; antiserum reaction to determine V. parahaemolyticus serotypes, and PCR assays were performed to identify pathogenic (tdh and/or trh) or pandemic (toxRS/new, and/or orf8) strains and antibiotic resistance testing. A total of 441 oyster samples were collected and tested for V. parahaemolyticus. Forty-seven percent of oyster samples were positive for V. parahaemolyticus. Ten different O serogroups and 72 serovars were identified, predominantly serotype O1:KUT with 22.2% and OUT:KUT with 17.3%. Twenty new serotypes that had not been previously reported in our region were identified. We detected 4.3% of pathogenic clones but no pandemic strains. About 73.5% of strains were resistant to at least one antibiotic, mainly ampicillin and ciprofloxacin; 25% were multi-drug resistant. In conclusion, the pathogenic strains in oysters and antibiotic resistance are of public health concern, as the potential for outbreaks throughout northwestern Mexico is well established.

Evolutionary dynamics of the successful expansion of pandemic Vibrio parahaemolyticus ST3 in Latin America

The underlying evolutionary mechanisms driving global expansions of pathogen strains are poorly understood. Vibrio parahaemolyticus is one of only two marine pathogens where variants have emerged in distinct climates globally. The success of a Vibrio parahaemolyticus clone (VpST3) in Latin America- the first spread identified outside its endemic region of tropical Asia- provided an invaluable opportunity to investigate mechanisms of VpST3 expansion into a distinct marine climate. A global collection of VpST3 isolates and novel Latin American isolates were used for evolutionary population genomics, pangenome analysis and combined with oceanic climate data. We found a VpST3 population (LatAm-VpST3) introduced in Latin America well before the emergence of this clone in India, previously considered the onset of the VpST3 epidemic. LatAm-VpST3 underwent successful adaptation to local conditions over its evolutionary divergence from Asian VpST3 isolates, to become dominant in Latin America. Selection signatures were found in genes providing resilience to the distinct marine climate. Core genome mutations and accessory gene presences that promoted survival over long dispersals or increased environmental fitness were associated with environmental conditions. These results provide novel insights into the global expansion of this successful V. parahaemolyticus clone into regions with different climate scenarios.

Efficacy of commercial peroxyacetic acid on Vibrio parahaemolyticus planktonic cells and biofilms on stainless steel and Greenshell™ mussel (Perna canaliculus) surfaces

The potential of using commercial peroxyacetic acid (PAA) for Vibrio parahaemolyticus sanitization was evaluated. Commercial PAA of 0.005 % (v/v, PAA: 2.24 mg/L, hydrogen peroxide: 11.79 mg/L) resulted in a planktonic cell reduction of >7.00 log10 CFU/mL when initial V. parahaemolyticus cells averaged 7.64 log10 CFU/mL. For cells on stainless steel coupons, treatment of 0.02 % PAA (v/v, PAA: 8.96 mg/L, hydrogen peroxide: 47.16 mg/L) achieved >5.00 log10 CFU/cm2 reductions in biofilm cells for eight strains but not for the two strongest biofilm formers. PAA of 0.05 % (v/v, PAA: 22.39 mg/L, hydrogen peroxide: 117.91 mg/L) was required to inactivate >5.00 log10 CFU/cm2 biofilm cells from mussel shell surfaces. The detection of PAA residues after biofilm treatment demonstrated that higher biofilm production resulted in higher PAA residues (p < 0.05), suggesting biofilm is acting as a barrier interfering with PAA diffusing into the matrices. Based on the comparative analysis of genomes, robust biofilm formation and metabolic heterogeneity within niches might have contributed to the variations in PAA resistance of V. parahaemolyticus biofilms.

Environmental Reservoirs of Pathogenic Vibrio spp. and Their Role in Disease: The List Keeps Expanding

Vibrio species are natural inhabitants of aquatic environments and have complex interactions with the environment that drive the evolution of traits contributing to their survival. These traits may also contribute to their ability to invade or colonize animal and human hosts. In this review, we attempt to summarize the relationships of Vibrio spp. with other organisms in the aquatic environment and discuss how these interactions could potentially impact colonization of animal and human hosts.

Vibrio parahaemolyticus Epidemiology and Pathogenesis: Novel Insights on an Emerging Foodborne Pathogen

The epidemiological dynamics of V. parahaemolyticus´ infections have been characterized by the abrupt appearance of outbreaks in remote areas where these diseases had not been previously detected, without knowing the routes of entry of the pathogens in the new area. However, there are recent studies that show the link between the appearance of epidemic outbreaks of Vibrio and environmental factors such as oceanic transport of warm waters, which has provided a possible mechanism for the dispersion of Vibrio diseases globally. Despite this evidence, there is little information on the possible routes of entry and transport of infectious agents from endemic countries to the entire world. In this sense, the recent advances in genomic sequencing tools are making it possible to infer possible biogeographical patterns of diverse pathogens with relevance in public health like V. parahaemolyticus. In this chapter, we will address several general aspects about V. parahaemolyticus, including their microbiological and genetic detection, main virulence factors, and the epidemiology of genotypes involved in foodborne outbreaks globally.

Growth Rates of Vibrio parahaemolyticus Sequence Type 36 Strains in Live Oysters and in Culture Medium

The pathogenic marine bacterium Vibrio parahaemolyticus can cause seafood-related gastroenteritis via the consumption of raw or undercooked seafood. Infections originating from relatively cool waters in the northeast United States are typically rare, but recently, this region has shown an increase in infections attributed to the ecological introduction of pathogenic sequence type 36 (ST36) strains, which are endemic to the cool waters of the Pacific Northwest. A 2005 risk assessment performed by the Food and Drug Administration (FDA) modeled the postharvest growth of V. parahaemolyticus in oysters as a function of air temperature and the length of time the oysters remained unrefrigerated. This model, while useful, has raised questions about strain growth differences in oyster tissue and whether invasive pathogenic strains exhibit different growth rates than nonclinical strains, particularly at lower temperatures. To investigate this question, live eastern oysters were injected with ST36 clinical strains and non-ST36 nonclinical strains, and growth rates were measured using the most probable number (MPN) enumeration. The presence of V. parahaemolyticus was confirmed using PCR by targeting the thermolabile hemolysin gene (tlh), thermostable direct hemolysin (tdh), tdh-related hemolysin (trh), and a pathogenesis-related protein (prp). The growth rates of the ST36 strains were compared to the FDA model and several other data sets of V. parahaemolyticus growth in naturally inoculated oysters harvested from the Chesapeake Bay. Our data indicate that the growth rates from most studies fall within the mean of the FDA model, but with slightly higher growth at lower temperatures for ST36 strains injected into live oysters. These data suggest that further investigations of ST36 growth capability in oysters at temperatures previously thought unsuitably low for Vibrio growth are warranted. IMPORTANCE Vibrio parahaemolyticus is the leading cause of seafood-related gastroenteritis in the United States, with an estimated 45,000 cases per year. Most individuals who suffer from vibriosis consume raw or undercooked seafood, including oysters. While gastroenteritis vibriosis is usually self-limiting and treatable, V. parahaemolyticus infections are a stressor on the growing aquaculture industry. Much effort has been placed on modeling the growth of Vibrio cells in oysters in order to aid oyster growers in designing harvesting best practices and ultimately, to protect the consumer. However, ecological invasions of nonnative bacterial strains make modeling their growth complicated, as these strains are not accounted for in current models. The National Shellfish Sanitation Program (NSSP) considers 10°C (50°F) a temperature too low to enable Vibrio growth, where 15°C is considered a cutoff temperature for optimal Vibrio growth, with temperatures approaching 20°C supporting higher growth rates. However, invasive strains may be native to cooler waters. This research aimed to understand strain growth in live oysters by measuring growth rates when oysters containing ST36 strains, which may be endemic to the U.S. Pacific Northwest, were exposed to multiple temperatures postharvest. Our results will be used to aid future model development and harvesting best practices for the aquaculture industry.

Serological and Antibiotic Resistance Patterns As Well As Molecular Characterization of Vibrio parahaemolyticus Isolated from Coastal Waters in the Eastern Province of Saudi Arabia

Vibrio parahaemolyticus belongs to the halophilic genus of Vibrionaceae family that inhabits coastal and marine environments and is a major food-borne pathogen. In the Gulf Cooperation Council (GCC) countries and Saudi Arabia in particular, there is a lack of information regarding the detection of pandemic clone or serovariants of V. parahaemolyticus pandemic clones. Here, 400 seawater samples were collected and examined for the presence of V. parahaemolyticus from 10 locations along the coast of Eastern Province in Saudi Arabia. The recovered isolates were serotyped, and studied for antimicrobial resistance, virulence genes, and markers of pandemicity using PCR and Arbitrarily primed (AP)-PCR typing patterns. All 40 isolates were tested negative for tdh, trh, and toxRS genes. Six serotypes were identified and three were clinically significant. Antibiotic susceptibility testing of isolates revealed high resistance towards penicillins, cephalosporins, and polymyxin; 60% of isolates were multi-drug resistant, whereas all isolates were susceptible to quinolones, carbapenems, sulfonamides, and tetracycline. The multiple antibiotic resistance (MAR) index among antibiotic resistance patterns of isolates revealed that 12 (30%) isolates had recorded significant MAR index higher than 0.2. AP-PCR fingerprinting could group all isolates into five distinct and identical pattern clusters with more than 85% similarity. Our findings demonstrate that pandemic serovariants of pandemic clones were not exclusively limited to strains isolated from fecal specimens of infected patients. Nine environmental strains of serotype O1:KUT, O1: K25, and O5:K17 were isolated from costal seawater, and thus the spread of these serovariants strains of pandemic clone of V. parahaemolyticus in the environment is to avoid any kind of threat to public health.

Vibrio parahaemolyticus Is Associated with Diarrhea Cases in Mexico, with a Dominance of Pandemic O3:K6 Clones

In the present study, we conducted surveillance of the V. parahaemolyticus strains present in clinical samples from six geographical regions of Mexico (22 states) from 2004 to 2011. The serotype dominance, virulence genes, presence of pandemic O3:K6 strains, and antibiotic resistance of the isolates were investigated. In total, 144 strains were isolated from the clinical samples. Seven different O serogroups and twenty-five serovars were identified. Most clinical isolates (66%, 95/144) belonged to the pandemic clone O3:K6 (tdh+, toxRS/new+ and/or orf8+) and were detected in 20 of the 22 states. Among the pandemic clones, approximately 17.8% (17/95) of the strains cross-reacted with the antisera for the K6 and K59 antigens (O3:K6, K59 serotype). Other pathogenic strains (tdh+ and/or trh+, toxRS/new-, orf8-) accounted for 26.3%, and the nonpathogenic strains (tdh- and/or trh-) accounted for 7.6%. Antimicrobial susceptibility testing showed that most of the strains were resistant to ampicillin (99.3%) but were sensitive to most tested antibiotics. The level of multidrug resistance was 1.3%. Our results indicate that pandemic O3:K6 is present in most Mexican states, thus, constant surveillance of V. parahaemolyticus strains in diarrhea patients is a public health priority and is useful for conducting risk assessments of foodborne illnesses to prevent V. parahaemolyticus outbreaks. Overall, our observations indicate that the pandemic O3:K6 clone of V. parahaemolyticus has become a relatively stable subpopulation and may be endemically established in Mexico; therefore, constant surveillance is needed to avoid new outbreaks of this pathogen.

Genomic Characterization of Ciprofloxacin Resistance in Laboratory-Derived Mutants of Vibrio parahaemolyticus

The quinolone ciprofloxacin is a broad-spectrum bactericidal antibiotic used for human medicine as well as the aquaculture industry. The emergence of ciprofloxacin-resistant Vibrio parahaemolyticus strains is currently a global public health concern. However, the mechanism of ciprofloxacin resistance in V. parahaemolyticus is not yet fully clarified. We generated mutants with decreased ciprofloxacin susceptibility using in vitro selection and investigated genes associated with ciprofloxacin resistance on a genetic level. Our selection process yielded mutants that possessed altered minimal inhibitory concentrations (MICs) for ciprofloxacin and other unrelated antibiotics. These included Ser83Ile mutations in GyrA and Val461Glu in ParE as well as mutations in the resistance nodulation cell division (RND) family transporter gene vmeD and the putative TetR family regulator gene vp0040 upstream of the vmeCD operon. Measurements of steady-state mRNA levels revealed that the ciprofloxacin-resistant mutants overexpressed vmeCD. Further, the introduction of the vp0040 mutated allele from H512 into the sensitive parental strain increased the MIC for ciprofloxacin 31.25-fold. Taken together, these results indicated that ciprofloxacin resistance in these mutants was due to the quinolone resistance determining region mutation as well as overexpression of vmeCD caused by a loss of vp0040 gene repression. This also accounted for the presence of the multidrug resistance phenotype for these mutant strains since RND efflux system can export structurally unrelated antibiotics.

The increased prevalence of Vibrio species and the first reporting of Vibrio jasicida and Vibrio rotiferianus at UK shellfish sites

Warming sea-surface temperature has led to an increase in the prevalence of Vibrio species in marine environments. This can be observed particularly in temperate regions where conditions for their growth has become more favourable. The increased prevalence of pathogenic Vibrio species has resulted in a worldwide surge of Vibriosis infections in human and aquatic animals. This study uses sea-surface temperature data around the English and Welsh coastlines to identify locations where conditions for the presence and growth of Vibrio species is favourable. Shellfish samples collected from three locations that were experiencing an increase in sea-surface temperature were found to be positive for the presence of Vibrio species. We identified important aquaculture pathogens Vibrio rotiferianus and Vibrio jasicida from these sites that have not been reported in UK waters. We also isolated human pathogenic Vibrio species including V. parahaemolyticus from these sites. This paper reports the first isolation of V. rotiferianus and V. jasicida from UK shellfish and highlights a growing diversity of Vibrio species inhabiting British waters.

Genomic stability among O3:K6 V. parahaemolyticus pandemic strains isolated between 1996 to 2012 in American countries

BACKGROUND

The V. parahaemolyticus pandemic clone, results in the development of gastrointestinal illness in humans. Toxigenic strains of this species are frequently isolated from aquatic habitats and organisms such as mollusks and crustaceans. Reports on the isolation of the pandemic clone started in 1996, when a new O3:K6 clone was identified in Asia, that rapidly spread worldwide, becoming the predominant clone isolated from clinical cases. In this study whole genome sequencing was accomplished with an Illumina MiniSeq platform, upon six novel V. parahaemolyticus strains, that have been isolated in Mexico since 1998 and three representative genomes of strains that were isolated from reported outbreaks in other American countries, and were deposited in the GenBank. These nine genomes were compared against the reference sequence of the O3:K6 pandemic strain (RIMD 2210633), which was isolated in 1996, to determine sequence differences within American isolates and between years of isolation.

RESULTS

The results indicated that strains that were isolated at different times and from different countries, were highly genetically similar, among them as well as to the reference strain RIMD 2210633, indicating a high level of genetic stability among the strains from American countries between 1996 to 2012, without significant genetic changes relative to the reference strain RIMD 2210633, which was isolated in 1996 and was considered to be representative of a novel O3:K6 pandemic strain.

CONCLUSIONS

The genomes of V. parahaemolyticus strains isolated from clinical and environmental sources in Mexico and other American countries, presented common characteristics that have been reported for RIMD 2210633 O3:K6 pandemic strain. The major variations that were registered in this study corresponded to genes non associated to virulence factors, which could be the result of adaptations to different environmental conditions. Nevertheless, results do not show a clear pattern with the year or locality where the strains were isolated, which is an indication of a genomic stability of the studied strains.

Genome analysis of Salmonella strains isolated from imported frozen fish in Burkina Faso

Purpose

Fish is an excellent source of protein and vitamins for humans, but improperly handled, fish can expose consumers to pathogenic bacteria. This study was aimed to isolate and characterize the genomes of Salmonella strains isolated from imported fish sold in the open market in Ouagadougou.

Methods

One hundred and fifty-nine fish were collected from open markets and were cultured for Salmonella. Antimicrobial susceptibility was determined by broth microdilution. Whole-genome sequencing was done to further study antibiotic resistance genes, plasmid replicons, and MSLT types. Serotyping was done using SeqSero 2.

Result

Out of the 159 fish samples analyzed, 30 (18.9%) were found to be contaminated with Salmonella. Among the isolated Salmonella strains, six different serotypes, Nima, Liverpool, Kokomlemle, Teshie, Derby, and Tennessee, were found using SeqSero2. Salmonella Tennessee was the predominant serotype. All the isolates possessed at least one resistance gene. The aac6-Iaa aminoglycoside resistance gene was the most prevalent gene found in the strains. The gene fosA7 was detected in three strains. All the S. Nima isolates were of Multilocus Sequence Type (MLST) 8086, S. Teshie isolate was ST 530; Liverpool was ST 1959; Derby was ST 7880; Kokomlemle was ST 2696. The Tennessee isolates gave two different STs including ST 8395 and 8398.

Conclusion

The presented results highlight the prevalence of Salmonella on imported fish purchased from the open markets. More attention should be paid regarding fish selling conditions in the country to prevent the potential health risk for consumers.

Longitudinal Study of Total and Pathogenic Vibrio parahaemolyticus (tdh+ and/or trh+) in Two Natural Extraction Areas of Mytilus chilensis in Southern Chile

Vibrio parahaemolyticus is the leading cause of seafood-associated bacterial gastroenteritis worldwide. Although different studies have focused on its pattern of variation over time, knowledge about the environmental factors driving the dynamics of this pathogen, within the Chilean territory, is still lacking. This study determined the prevalence of total and pathogenic V. parahaemolyticus strains (tdh and/or trh genes) in mussels (Mytilus chilensis) collected from two natural growing areas between 2017 and 2018, using selective agar and PCR analysis. V. parahaemolyticus was detected in 45.6% (93/204) of pooled samples from the Valdivia River Estuary. The pathogenic strains carrying the tdh and/or trh gene were detected in 11.8% (24/204): tdh in 9.8% (20/204), trh in 0.5% (1/204), and 1.5% (3/204) presented both genes. In Reloncaví Fjord, V. parahaemolyticus was detected in 14.4% (30/209) of the samples, pathogenic V. parahaemolyticus carrying the trh gene was detected in 0.5% (1/209) of the samples, while the tdh gene was not detected in the samples from this area. The total count of mauve-purple colonies typical of V. parahaemolyticus on CHROMagar was positively associated by multivariate analysis with area, water temperature, and salinity. Similarly, V. parahaemolyticus detection rates by PCR had a positive correlation with the area and water temperature. The chances of detecting total V. parahaemolyticus in the Valdivia River Estuary are significantly higher than in the Reloncaví Fjord, but inversely, during spring-summer months, the interaction factor between the area and temperature indicated that the chances of detecting V. parahaemolyticus are higher in the Reloncaví Fjord. Interestingly, this period coincides with the season when commercial and natural-growing shellfish are harvested. On the other hand, pathogenic V. parahaemolyticus tdh+ was significantly correlated with an increase of water temperature. These environmental parameters could be used to trigger a warning on potential hazard, which would influence human health and economic losses in aquaculture systems.

Characterization of Pathogenic Vibrio parahaemolyticus Isolated From Fish Aquaculture of the Southwest Coastal Area of Bangladesh

Vibrio parahaemolyticus is a major foodborne pathogen responsible for significant economic losses in aquaculture and a threat to human health. Here, we explored the incidence, virulence potential, and diversity of V. parahaemolyticus isolates from aquaculture farms in Bangladesh. We examined a total of 216 water, sediment, Oreochromis niloticus (tilapia), Labeo rohita (rui), and Penaeus monodon (shrimp) samples from the aquaculture system where 60.2% (130/216) samples were positive for V. parahaemolyticus. Furthermore, we identified 323 V. parahaemolyticus strains from contaminated samples, 17 of which were found positive for trh, a virulence gene. Four isolates out of the 17 obtained were able to accumulate fluid in the rabbit ileal loop assay. The correlation between the contamination of V. parahaemolyticus and environmental factors was determined by Pearson correlation. The temperature and salinity were significantly correlated (positive) with the incidence of V. parahaemolyticus. Most of the pathogenic isolates (94.1%) were found resistant to ampicillin and amoxicillin. O8: KUT was the predominant serotype of the potentially pathogenic isolates. ERIC-PCR reveals genetic variation and relatedness among the pathogenic isolates. Therefore, this region-specific study establishes the incidence of potential infection with V. parahaemolyticus from the consumption of tilapia, rui, and shrimp raised in farms in Satkhira, Bangladesh, and the basis for developing strategies to reduce the risk for diseases and economic burden.

Global Expansion of Pacific Northwest Vibrio parahaemolyticus Sequence Type 36

We report transcontinental expansion of Vibrio parahaemolyticus sequence type 36 into Lima, Peru. From national collections, we identified 7 isolates from 2 different Pacific Northwest complex lineages that surfaced during 2011–2016. Sequence type 36 is likely established in environmental reservoirs. Systematic surveillance enabled detection of these epidemic isolates.

Co-existence of multiple distinct lineages in Vibrio parahaemolyticus serotype O4:K12

Vibrio parahaemolyticus is an important cause of foodborne gastroenteritis globally. Thermostable direct haemolysin (TDH) and the TDH-related haemolysin are the two key virulence factors in V. parahaemolyticus. Vibrio pathogenicity islands harbour the genes encoding these two haemolysins. The serotyping of V. parahaemolyticus is based on the combination of O and K antigens. Frequent recombination has been observed in V. parahaemolyticus, including in the genomic regions encoding the O and K antigens. V. parahaemolyticus serotype O4:K12 has caused gastroenteritis outbreaks in the USA and Spain. Recently, outbreaks caused by this serotype of V. parahaemolyticus have been reported in China. However, the relationships among this serotype of V. parahaemolyticus strains isolated in different regions have not been addressed. Here, we investigated the genome variation of the V. parahaemolyticus serotype O4:K12 using the whole-genome sequences of 29 isolates. We determined five distinct lineages in this strain collection. We observed frequent recombination among different lineages. In contrast, little recombination was observed within each individual lineage. We showed that the lineage of this serotype of V. parahaemolyticus isolated in America was different from those isolated in Asia and identified genes that exclusively existed in the strains isolated in America. Pan-genome analysis showed that strain-specific and cluster-specific genes were mostly located in the genomic islands. Pan-genome analysis also showed that the vast majority of the accessory genes in the O4:K12 serotype of V. parahaemolyticus were acquired from within the genus Vibrio. Hence, we have shown that multiple distinct lineages exist in V. parahaemolyticus serotype O4:K12 and have provided more evidence about the gene segregation found in V. parahaemolyticus isolated in different continents.

Managing the risk of Vibrio parahaemolyticus infections associated with oyster consumption: A review

Vibrio parahaemolyticus is a Gram-negative bacterium that is naturally present in the marine environment. Oysters, which are water filter feeders, may accumulate this pathogen in their soft tissues, thus increasing the risk of V. parahaemolyticus infection among people who consume oysters. In this review, factors affecting V. parahaemolyticus accumulation in oysters, the route of the pathogen from primary production to consumption, and the potential effects of climate change were discussed. In addition, intervention strategies for reducing accumulation of V. parahaemolyticus in oysters were presented. A literature review revealed the following information relevant to the present study: (a) managing the safety of oysters (for human consumption) from primary production to consumption remains a challenge, (b) there are multiple factors that influence the concentration of V. parahaemolyticus in oysters from primary production to consumption, (c) climate change could possibly affect the safety of oysters, both directly and indirectly, placing public health at risk, (d) many intervention strategies have been developed to control and/or reduce the concentration of V. parahaemolyticus in oysters to acceptable levels, but most of them are mainly focused on the downstream steps of the oyster supply chain, and (c) although available regulation and/or guidelines governing the safety of oyster consumption are mostly available in developed countries, limited food safety information is available in developing countries. The information provided in this review may serve as an early warning for managing the future effects of climate change on the safety of oyster consumption.

Nuclear magnetic resonance biosensor for rapid detection of Vibrio parahaemolyticus

BACKGROUND

Vibrio parahaemolyticus is a Gram-negative bacterium widely distributed in marine environments and a well-recognized invertebrate pathogen frequently isolated from seafood. V. parahaemolyticus may also spread into humans, via contaminated, raw, or undercooked seafood, causing gastroenteritis and diarrhea.

METHODS

A Nuclear Magnetic Resonance (NMR)-based detection system was used to detect pathogenic levels of this microorganism (105 CFU/ml) with Molecular Mirroring using iron nanoparticles coated with target-specific biomarkers capable of binding to DNA of the target microorganism. The NMR system generates a signal (in milliseconds) by measuring NMR spin-spin relaxation time T2, which correlates with the amount of microorganism DNA.

RESULTS

Compared with conventional microbiology techniques such as real-time PCR (qPCR), the NMR biosensor showed similar limits of detection (LOD) at different concentrations (105-108 CFU/ml) using two DNA extraction methods. In addition, the NMR biosensor system can detect a wide range of microorganism DNAs in different matrices within a short period of time.

CONCLUSION

NMR biosensor represents a potential tool for diagnostic and quality control to ensure microbial pathogens such as V. parahaemolyticus are not the cause of infection. The "hybrid" technology (NMR and nanoparticle application) opens a new platform for detecting other microbial pathogens that have impacted human health, animal health and food safety.

Vibriosis in Fish: A Review on Disease Development and Prevention

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of the global aquaculture industry. Vibriosis is among the most common diseases leading to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and grow-out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, environmental factors (including water quality and farm management), and the virulence factors of Vibrio, influence the occurrence of the disease. Affected fish show weariness, with necrosis of skin and appendages, leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. A combination of control measures, particularly a disease-free source of fish, biosecurity of the farm, improved water quality, and other preventive measures (e.g., vaccination) might be able to control the infection. Although some control measures are expensive and less practical, vaccination is effective, relatively cheap, and easily implemented. In this review, the latest knowledge on the pathogenesis and control of vibriosis, including vaccination, is discussed.

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.

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.

Prospects for Biocontrol of Vibrio parahaemolyticus Contamination in Blue Mussels (Mytilus edulus)-A Year-Long Study

Vibrio parahaemolyticus is an environmental organism normally found in subtropical estuarine environments which can cause seafood-related human infections. Clinical disease is associated with diagnostic presence of tdh and/or trh virulence genes and identification of these genes in our preliminary isolates from retail shellfish prompted a year-long surveillance of isolates from a temperate estuary in the north of England. The microbial and environmental analysis of 117 samples of mussels, seawater or sediment showed the presence of V. parahaemolyticus from mussels (100%) at all time-points throughout the year including the colder months although they were only recovered from 94.9% of seawater and 92.3% of sediment samples. Throughout the surveillance, 96 isolates were subjected to specific PCR for virulence genes and none tested positive for either. The common understanding that consuming poorly cooked mussels only represents a risk of infection during summer vacations therefore is challenged. Further investigations with V. parahaemolyticus using RAPD-PCR cluster analysis showed a genetically diverse population. There was no distinct clustering for “environmental” or “clinical” reference strains although a wide variability and heterogeneity agreed with other reports. Continued surveillance of isolates to allay public health risks are justified since geographical distribution and composition of V. parahaemolyticus varies with Future Ocean warming and the potential of environmental strains to acquire virulence genes from pathogenic isolates. The prospects for intervention by phage-mediated biocontrol to reduce or eradicate V. parahaemolyticus in mussels was also investigated. Bacteriophages isolated from enriched samples collected from the river Humber were assessed for their ability to inhibit the growth of V. parahaemolyticus strains in-vitro and in-vivo (with live mussels). V. parahaemolyticus were significantly reduced in-vitro, by an average of 1 log−2 log units and in-vivo, significant reduction of the organisms in mussels occurred in three replicate experimental tank set ups with a “phage cocktail” containing 12 different phages. Our perspective biocontrol study suggests that a cocktail of specific phages targeted against strains of V. parahaemolyticus provides good evidence in an experimental setting of the valuable potential of phage as a decontamination agent in natural or industrial mussel processing (343w).

Heat Wave-Associated Vibriosis, Sweden and Finland, 2014

During summer 2014, a total of 89 Vibrio infections were reported in Sweden and Finland, substantially more yearly infections than previously have been reported in northern Europe. Infections were spread across most coastal counties of Sweden and Finland, but unusually, numerous infections were reported in subarctic regions; cases were reported as far north as 65°N, ≈100 miles (160 km) from the Arctic Circle. Most infections were caused by non-O1/O139 V. cholerae (70 cases, corresponding to 77% of the total, all strains were negative for the cholera toxin gene). An extreme heat wave in northern Scandinavia during summer 2014 led to unprecedented high sea surface temperatures, which appear to have been responsible for the emergence of Vibrio bacteria at these latitudes. The emergence of vibriosis in high-latitude regions requires improved diagnostic detection and clinical awareness of these emerging pathogens.

Environmental Suitability of Vibrio Infections in a Warming Climate: An Early Warning System

BACKGROUND

Some Vibrio spp. are pathogenic and ubiquitous in marine waters with low to moderate salinity and thrive with elevated sea surface temperature (SST).

OBJECTIVES

Our objective was to monitor and project the suitability of marine conditions for Vibrio infections under climate change scenarios.

METHODS

The European Centre for Disease Prevention and Control (ECDC) developed a platform (the ECDC Vibrio Map Viewer) to monitor the environmental suitability of coastal waters for Vibrio spp. using remotely sensed SST and salinity. A case-crossover study of Swedish cases was conducted to ascertain the relationship between SST and Vibrio infection through a conditional logistic regression. Climate change projections for Vibrio infections were developed for Representative Concentration Pathway (RCP) 4.5 and RCP 8.5.

RESULTS

The ECDC Vibrio Map Viewer detected environmentally suitable areas for Vibrio spp. in the Baltic Sea in July 2014 that were accompanied by a spike in cases and one death in Sweden. The estimated exposure-response relationship for Vibrio infections at a threshold of 16°C revealed a relative risk (RR)=1.14 (95% CI: 1.02, 1.27; p=0.024) for a lag of 2 wk; the estimated risk increased successively beyond this SST threshold. Climate change projections for SST under the RCP 4.5 and RCP 8.5 scenarios indicate a marked upward trend during the summer months and an increase in the relative risk of these infections in the coming decades.

CONCLUSIONS

This platform can serve as an early warning system as the risk of further Vibrio infections increases in the 21st century due to climate change. https://doi.org/10.1289/EHP2198.

Preharvest Food Safety Under the Influence of a Changing Climate

Ensuring food safety and addressing the impact of climate change are both immense concepts. Food production systems must continue to evolve in order to develop food safety management programs and identify emerging risks linked to climate change. There are an infinite number of crosscutting issues regarding climate change and health. The changing climate of the globe manifests itself in fluctuating temperatures, intense storms, droughts, and fluctuating sea levels. These environmental variables in turn may increase the risk of foodborne disease transmission through our foods and increase the need for vigilance and risk mitigation at the preharvest level. While the influence of climate change is untold, four cases are discussed here, including waterborne disease, seafood, production of fruits and vegetables, and mycotoxins. Changes relative to climate have been documented at the preharvest level for these issues. Change must be addressed alongside education and research to safeguard the human health effects of climate change.

Gene expression of Vibrio parahaemolyticus growing in laboratory isolation conditions compared to those common in its natural ocean environment

BACKGROUND

Vibrio parahaemolyticus is an autochthonous marine bacterial species comprising strains able to grow in broth containing bile salts at 37 °C, a condition seldom found in the ocean. However, this condition is used for isolation in the laboratory because it is considered a necessary property for pathogenesis. In this context, revealing how gene expression enables V. parahaemolyticus to adapt to this particular condition -common to almost all V. parahaemolyticus isolates- will improve our understanding of the biology of this important pathogen. To determine the genes of V. parahaemolyticus differentially expressed when growing in isolation condition (37 °C, 0.9% NaCl, and 0.04% bile salts) referred to those at the temperature and salt concentration prevailing in ocean south of Chile (marine-like condition; 12 °C, 3% NaCl, and absence of bile salts) we used high-throughput sequencing of RNA.

RESULTS

Our results showed that in the isolation condition, among the 5034 genes annotated in the V. parahaemolyticus RIMD2210633 genome, 344 were upregulated and 433 downregulated referred to the marine-like condition, managing an adjusted P-value (Padj) < E-5. Between the 50 more highly expressed genes, among the small RNAs (sRNA), the three carbon storage regulators B (CsrB) were up four to six times, while RyhB, related to iron metabolism besides motility control, was down about eight times. Among proteins, BfdA, a hemolysin-co-regulated protein (Hcp1) secreted by T6SS1, one of the most highly expressed genes, was about 140 times downregulated in isolation condition. The highest changes in relative expression were found among neighboring genes coding for proteins related to respiration, which were about 40 times upregulated.

CONCLUSIONS

When V. parahaemolyticus is grown in conditions used for laboratory isolation 777 genes are up- or downregulated referred to conditions prevailing in the marine-like condition; the most significantly overrepresented categories among upregulated processes were those related to transport and localization, while secretion and pathogenesis were overrepresented among downregulated genes. Genes with the highest differential expression included the sRNAs CsrB and RhyB and the mRNAs related with secretion, nutritional upshift, respiration and rapid growing.

Defining a Core Genome Multilocus Sequence Typing Scheme for the Global Epidemiology of Vibrio parahaemolyticus

Vibrio parahaemolyticus is an important human foodborne pathogen whose transmission is associated with the consumption of contaminated seafood, with a growing number of infections reported over recent years worldwide. A multilocus sequence typing (MLST) database for V. parahaemolyticus was created in 2008, and a large number of clones have been identified, causing severe outbreaks worldwide (sequence type 3 [ST3]), recurrent outbreaks in certain regions (e.g., ST36), or spreading to other regions where they are nonendemic (e.g., ST88 or ST189). The current MLST scheme uses sequences of 7 genes to generate an ST, which results in a powerful tool for inferring the population structure of this pathogen, although with limited resolution, especially compared to pulsed-field gel electrophoresis (PFGE). The application of whole-genome sequencing (WGS) has become routine for trace back investigations, with core genome MLST (cgMLST) analysis as one of the most straightforward ways to explore complex genomic data in an epidemiological context. Therefore, there is a need to generate a new, portable, standardized, and more advanced system that provides higher resolution and discriminatory power among V. parahaemolyticus strains using WGS data. We sequenced 92 V. parahaemolyticus genomes and used the genome of strain RIMD 2210633 as a reference (with a total of 4,832 genes) to determine which genes were suitable for establishing a V. parahaemolyticus cgMLST scheme. This analysis resulted in the identification of 2,254 suitable core genes for use in the cgMLST scheme. To evaluate the performance of this scheme, we performed a cgMLST analysis of 92 newly sequenced genomes, plus an additional 142 strains with genomes available at NCBI. cgMLST analysis was able to distinguish related and unrelated strains, including those with the same ST, clearly showing its enhanced resolution over conventional MLST analysis. It also distinguished outbreak-related from non-outbreak-related strains within the same ST. The sequences obtained from this work were deposited and are available in the public database (http://pubmlst.org/vparahaemolyticus). The application of this cgMLST scheme to the characterization of V. parahaemolyticus strains provided by different laboratories from around the world will reveal the global picture of the epidemiology, spread, and evolution of this pathogen and will become a powerful tool for outbreak investigations, allowing for the unambiguous comparison of strains with global coverage.

Season-Specific Occurrence of Potentially Pathogenic Vibrio spp. on the Southern Coast of South Korea

Vibrio species are widely distributed in warm estuarine and coastal environments, and they can infect humans through the consumption of raw and mishandled contaminated seafood. In this study, we aimed to isolate and observe the distribution of enteropathogenic Vibrio spp. from environments of the southern coast of South Korea over a season cycle. A total of 10,983 isolates of Vibrio spp. were obtained from tidal water and mud samples over a 1-year period from five sampling sites along the southwest coast of South Korea. We found that Vibrio alginolyticus (n = 6,262) and Vibrio parahaemolyticus (n = 1,757) were ubiquitous in both tidal water and mud year round, whereas Vibrio cholerae (n = 24) and Vibrio vulnificus (n = 130) were seasonally specific to summer. While all V. cholerae isolates were nontoxigenic (non-O1 and non-O139), more than 88% of V. vulnificus isolates possessed the virulence factor elastolytic protease (encoded by vvp). Interestingly, V. parahaemolyticus, which was omnipresent in all seasons, contained the virulence factors thermostable direct hemolysin (encoded by tdh) and thermostable direct hemolysin-related hemolysin (encoded by trh) in larger amounts in June (29 trh-positive strains) and September (14 tdh-, 36 trh-, and 12 tdh- and trh-positive strains) than in December (4 trh-positive strains) and February (3 tdh-positive strains), and virulence factors were absent from isolates detected in April. To understand why virulence factors were detected only in the warm season and were absent in the cold season although the locations are static, long-term monitoring and particularly seasonal study are necessary.

IMPORTANCE

The presence of enteropathogenic Vibrio species (Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus), which cause acute diarrheal infection, septicemia, and wound infections upon ingestion through food and water, is usually associated with temperature. The World Health Organization (WHO) has estimated that there are 1.4 to 4.3 million cases and 28,000 to 142,000 deaths per year worldwide caused by cholera disease. In South Korea alone, consumption is as much as 52.4 kg of fish and shellfish per year per capita. Our findings suggested that seasonally specific acceleration of these possible pathogenic Vibrio spp. may threaten seafood safety and increase the risk of illness in South Korea, where local people consume raw fish during warmer months.

Inactivation Kinetics ofVibrio parahaemolyticuson Sand Shrimp(Metapenaeus ensis)by Cinnamaldehyde at 4°C

Sand shrimp(Metapenaeus ensis), shrimp shell, and shrimp meat were inoculated with a three-strain cocktail ofVibrio parahaemolyticuswith or without the natural antimicrobial cinnamaldehyde (2.5 mg/ml) and were, then, stored at 4°C for up to 25 days and 18 inactivation curves were obtained.V. parahaemolyticuswere inactivated down to the minimum level of detection (2.48 log CFU/g) on thiosulfate citrate bile salts sucrose agar (TCBS) plates within 7 and 10 days with low and high densities ofV. parahaemolyticusinoculation, 4.5 log CFU/g and 8.2 log CFU/g, respectively. With adding cinnamaldehyde, the inactivation process ofV. parahaemolyticuswith low populations, 4.5 log CFU/g, lasted for only 4 days. Therefore, cinnamaldehyde inactivated cells faster as expected. However, unexpectedly, in shrimp meat cases, cells have much more persistence of over even 25 days before entering the minimum level of detection both with and without cinnamaldehyde treatment. Therefore, a hypothesis was formed that when cells kept in cold environments (4°C) after several days recovered to up to 103–104CFU/g towards the end of the experiments and with starvation (shell and shrimp studies), cells might render a viable but nonculturable (VBNC) state.

Characteristics of Vibrio parahaemolyticus isolates obtained from crayfish (Procambarus clarkii) in freshwater

Vibrio parahaemolyticus usually occurs in coastal areas and is generally recognized as a marine bacterium. It has become the leading cause of gastroenteritis worldwide. In the present study, 96 V. parahaemolyticus isolates were obtained from freshwater crayfish (Procambarus clarkii) and classified by multilocus sequence typing. Fifty-three sequence types (STs) were identified among the 96 isolates analyzed, 38 of which were novel STs. These isolates fell into six groups and 42 singletons, suggesting a high level of genetic diversity. Screening for 9 virulence and virulence-related genes in the isolates revealed that 40 isolates contained more than two genes with possible roles in pathogenicity. The virulence of the representative isolates VP66 (trh⁺, ureC⁺, T3SS1⁺, T3SS2β⁺, T6SS2⁺) and VP80 (T3SS1⁺, T6SS1⁺, T6SS2⁺) were further assessed in zebrafish and mouse infection model in vivo, and the tested isolates were shown to be lethal to both zebrafish and mice. These results suggest that crayfish may serve as a carrier of V. parahaemolyticus in freshwater, and that some isolates may have the potential to cause foodborne disease in humans.

Heat Wave-Associated Vibriosis, Sweden and Finland, 2014

During summer 2014, a total of 89 Vibrio infections were reported in Sweden and Finland, substantially more yearly infections than previously have been reported in northern Europe. Infections were spread across most coastal counties of Sweden and Finland, but unusually, numerous infections were reported in subarctic regions; cases were reported as far north as 65°N, ≈100 miles (160 km) from the Arctic Circle. Most infections were caused by non-O1/O139 V. cholerae (70 cases, corresponding to 77% of the total, all strains were negative for the cholera toxin gene). An extreme heat wave in northern Scandinavia during summer 2014 led to unprecedented high sea surface temperatures, which appear to have been responsible for the emergence of Vibrio bacteria at these latitudes. The emergence of vibriosis in high-latitude regions requires improved diagnostic detection and clinical awareness of these emerging pathogens.

Spatiotemporal Dynamics of Vibrio spp. within the Sydney Harbour Estuary

Vibrio are a genus of marine bacteria that have substantial environmental and human health importance, and there is evidence that their impact may be increasing as a consequence of changing environmental conditions. We investigated the abundance and composition of the Vibrio community within the Sydney Harbour estuary, one of the most densely populated coastal areas in Australia, and a region currently experiencing rapidly changing environmental conditions. Using quantitative PCR (qPCR) and Vibrio-specific 16S rRNA amplicon sequencing approaches we observed significant spatial and seasonal variation in the abundance and composition of the Vibrio community. Total Vibrio spp. abundance, derived from qPCR analysis, was higher during the late summer than winter and within locations with mid-range salinity (5-26 ppt). In addition we targeted three clinically important pathogens: Vibrio cholerae, V. Vulnificus, and V. parahaemolyticus. While toxigenic strains of V. cholerae were not detected in any samples, non-toxigenic strains were detected in 71% of samples, spanning a salinity range of 0-37 ppt and were observed during both late summer and winter. In contrast, pathogenic V. vulnificus was only detected in 14% of samples, with its occurrence restricted to the late summer and a salinity range of 5-26 ppt. V. parahaemolyticus was not observed at any site or time point. A Vibrio-specific 16S rRNA amplicon sequencing approach revealed clear shifts in Vibrio community composition across sites and between seasons, with several Vibrio operational taxonomic units (OTUs) displaying marked spatial patterns and seasonal trends. Shifts in the composition of the Vibrio community between seasons were primarily driven by changes in temperature, salinity and NO2, while a range of factors including pH, salinity, dissolved oxygen (DO) and NOx (Nitrogen Oxides) explained the observed spatial variation. Our evidence for the presence of a spatiotemporally dynamic Vibrio community within Sydney Harbour is notable given the high levels of human use of this waterway, and the significant increases in seawater temperature predicted for this region.

iTRAQ-based proteomic profiling of Vibrio parahaemolyticus under various culture conditions

Background

Vibrio parahaemolyticus is a common pathogen infecting humans and marine animals; this pathogen has become a major concern of marine food products and trade. In this study, V. parahaemolyticus isolated from sewage was exposed to different culture conditions and analyzed by isobaric tag for relative and absolute quantitation (iTRAQ) based reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique. Our goal is to gain further insights into the proteomics of V. parahaemolyticus, particularly differentially expressed proteins closely correlated with growth conditions and pathogenicity associated proteins.

Results

In this study, a total of 2,717 proteins including numerous membrane proteins were significantly identified, and 616 proteins displayed significant differential expression under different conditions. Of them, 12 proteins mainly participating in metabolism showed the most elastic expression differentiation between different culture conditions. Some membrane proteins such as type I secretion outer membrane protein, TolC, lipoprotein, efflux system proteins iron-regulated protein A and putaive Fe-regulated protein B, ferric siderophore receptor homolog and several V. parahaemolyticus virulence-associated proteins were differentially regulated under different conditions. Some differentially regulated proteins were analyzed and confirmed at gene expression level by quantitative real time polymerase chain reaction (qRT-PCR).

Conclusions

Proteomics analysis results revealed the characteristics of V. parahaemolyticus proteome expression, provided some promising biomarkers related with growth conditions, the results likely advance insights into the mechanism involved in the response of V. parahaemolyticus to different conditions. Some virulence-associated proteins were discovered to be differentially expressed under different conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-015-0075-4) contains supplementary material, which is available to authorized users.

A pandemic Vibrio parahaemolyticus O3:K6 clone causing most associated diarrhea cases in the Pacific Northwest coast of Mexico

Between September and October of 2004, more than 1230 cases of gastroenteritis due to pandemic O3:K6 strains of Vibrio parahaemolyticus (V. parahaemolyticus) were reported in the relatively small geographical area of Southern Sinaloa, a state located in Northwest Mexico. Since then, V. parahaemolyticus-associated gastroenteritis cases have gradually increased in prevalence spreading from south to north. The present study conducted an epidemiological surveillance of V. parahaemolyticus strains in both environmental and clinical samples along the Pacific coast of Sinaloa from 2011 to 2013. The genetic relatedness, serotype dominance and antibiotic resistance of isolates were investigated. A total of 46 strains were isolated from environmental samples (e.g., sediment, seawater and shrimp), whereas 249 strains were obtained from stools of patients with gastroenteritis. Nine different O serogroups and 16 serovars were identified. Serovars O3:K6 and O6:K46 were identified in both environmental and clinical strains. Whereas most environmental isolates carried the tdh gene (71.74%, 33/46), only three (6.52%) belonged to pandemic clones (O3:K6, O3:KUT and OUT:KUT). In contrast, 81.1% (202/249) of clinical isolates belonged to pandemic serotypes, with O3:K6 (tdh, toxRS/new, and/or orf8) representing the predominant serovar (97%, 196/202). This prevalence of pathogenic (tdh and/or trh positive) and O3:K6 pandemic V. parahaemolyticus isolates in this study were similar to those found from 2004 to 2010. As investigated by REP-PCR, genetic lineages of selected O3:K6 strains isolated in this study and some isolated earlier were nearly identical. Antimicrobial susceptibility testing showed that most strains (93.8%) were resistant to ampicillin but sensitive to chloramphenicol (98.8%). Multidrug resistance significantly increased from 8.6% (2004-2010) to 22.93% (2011-2013; p < 0.05). Our data indicate that pandemic O3:K6 clone has endemically established in the Pacific Coast of Mexico.

Genome diversification within a clonal population of pandemic Vibrio parahaemolyticus seems to depend on the life circumstances of each individual bacteria

Background

New strains of Vibrio parahaemolyticus that cause diarrhea in humans by seafood ingestion periodically emerge through continuous evolution in the ocean. Influx and expansion in the Southern Chilean ocean of a highly clonal V. parahaemolyticus (serotype O3:K6) population from South East Asia caused one of the largest seafood-related diarrhea outbreaks in the world. Here, genomics analyses of isolates from this rapidly expanding clonal population offered an opportunity to observe the molecular evolutionary changes often obscured in more diverse populations.

Results

Whole genome sequence comparison of eight independent isolates of this population from mussels or clinical cases (from different years) was performed. Differences of 1366 to 217,729 bp genome length and 13 to 164 bp single nucleotide variants (SNVs) were found. Most genomic differences corresponded to the presence of regions unique to only one or two isolates, and were probably acquired by horizontal gene transfer (HGT). Some DNA gain was chromosomal but most was in plasmids. One isolate had a large region (8,644 bp) missing, which was probably caused by excision of a prophage. Genome innovation by the presence of unique DNA, attributable to HGT from related bacteria, varied greatly among the isolates, with values of 1,366 (ten times the number of highest number of SNVs) to 217,729 (a thousand times more than the number of highest number of SNVs).

Conclusions

The evolutionary forces (SNVs, HGT) acting on each isolate of the same population were found to differ to an extent that probably depended on the ecological scenario and life circumstances of each bacterium.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1385-8) contains supplementary material, which is available to authorized users.

Characterization of Vibrio parahaemolyticus clinical strains from Maryland (2012-2013) and comparisons to a locally and globally diverse V. parahaemolyticus strains by whole-genome sequence analysis

Vibrio parahaemolyticus is the leading cause of foodborne illnesses in the US associated with the consumption of raw shellfish. Previous population studies of V. parahaemolyticus have used Multi-Locus Sequence Typing (MLST) or Pulsed Field Gel Electrophoresis (PFGE). Whole genome sequencing (WGS) provides a much higher level of resolution, but has been used to characterize only a few United States (US) clinical isolates. Here we report the WGS characterization of 34 genomes of V. parahaemolyticus strains that were isolated from clinical cases in the state of Maryland (MD) during 2 years (2012-2013). These 2 years saw an increase of V. parahaemolyticus cases compared to previous years. Among these MD isolates, 28% were negative for tdh and trh, 8% were tdh positive only, 11% were trh positive only, and 53% contained both genes. We compared this set of V. parahaemolyticus genomes to those of a collection of 17 archival strains from the US (10 previously sequenced strains and 7 from NCBI, collected between 1988 and 2004) and 15 international strains, isolated from geographically-diverse environmental and clinical sources (collected between 1980 and 2010). A WGS phylogenetic analysis of these strains revealed the regional outbreak strains from MD are highly diverse and yet genetically distinct from the international strains. Some MD strains caused outbreaks 2 years in a row, indicating a local source of contamination (e.g., ST631). Advances in WGS will enable this type of analysis to become routine, providing an excellent tool for improved surveillance. Databases built with phylogenetic data will help pinpoint sources of contamination in future outbreaks and contribute to faster outbreak control.

Environmental parameters influence on the dynamics of total and pathogenic Vibrio parahaemolyticus densities in Crassostrea virginica harvested from Mexico's Gulf coast

The influence of environmental parameters on the total and pathogenic Vibrio parahaemolyticus seasonal densities in American oysters (Crassostrea virginica) was evaluated for 1 year. Harvesting site A yielded the highest mean densities of V. parahaemolyticus tlh+, tdh+/trh-, tdh-/trh+ and tdh+/trh+ during spring season at 2.57, 1.74, 0.36, and -0.40 log10 MPN/g, respectively, and tdh+/orf8+ during winter season (0.90 log10 MPN/g). V. parahaemolyticus tlh+ densities were associated to salinity (R(2)=0.372, P<0.022), tdh+/trh+ to turbidity (R(2)=0.597, P<0.035), and orf8+ to temperature, salinity, and pH (R(2)=0.964, P<0.001). The exposure to salinity and temperature conditions during winter and spring seasons regulated the dynamics of V. parahaemolyticus harboring potentially pathogenic genotypes within the oyster. The adaptive response of V. parahaemolyticus to seasonal environmental changes may lead to an increase in survival and virulence, threatening the seafood safety and increasing the risk of illness.

Transoceanic spreading of pathogenic strains of Vibrio parahaemolyticus with distinctive genetic signatures in the recA gene

Vibrioparahaemolyticus is an important human pathogen whose transmission is associated with the consumption of contaminated seafood. Consistent multilocus sequence typing for V. parahaemolyticus has shown difficulties in the amplification of the recA gene by PCR associated with a lack of amplification or a larger PCR product than expected. In one strain (090–96, Peru, 1996), the produced PCR product was determined to be composed of two recA fragments derived from different Vibrio species. To better understand this phenomenon, we sequenced the whole genome of this strain. The hybrid recA gene was found to be the result of a fragmentation of the original lineage-specific recA gene resulting from a DNA insertion of approximately 30 kb in length. This insert had a G+C content of 38.8%, lower than that of the average G+C content of V. parahaemolyticus (45.2%), and contained 19 ORFs, including a complete recA gene. This new acquired recA gene deviated 24% in sequence from the original recA and was distantly related to recA genes from bacteria of the Vibrionaceae family. The reconstruction of the original recA gene (recA3) identified the precursor as belonging to ST189, a sequence type reported previously only in Asian countries. The identification of this singular genetic feature in strains from Asia reveals new evidence for genetic connectivity between V. parahaemolyticus populations at both sides of the Pacific Ocean that, in addition to the previously described pandemic clone, supports the existence of a recurrent transoceanic spreading of pathogenic V. parahaemolyticus with the corresponding potential risk of pandemic expansion.

Long-term study of Vibrio parahaemolyticus prevalence and distribution in New Zealand shellfish

The food-borne pathogen Vibrio parahaemolyticus has been reported as being present in New Zealand (NZ) seawaters, but there have been no reported outbreaks of food-borne infection from commercially grown NZ seafood. Our study determined the current incidence of V. parahaemolyticus in NZ oysters and Greenshell mussels and the prevalence of V. parahaemolyticus tdh and trh strains. Pacific (235) and dredge (21) oyster samples and mussel samples (55) were obtained from commercial shellfish-growing areas between December 2009 and June 2012. Total V. parahaemolyticus numbers and the presence of pathogenic genes tdh and trh were determined using the FDA most-probable-number (MPN) method and confirmed using PCR analysis. In samples from the North Island of NZ, V. parahaemolyticus was detected in 81% of Pacific oysters and 34% of mussel samples, while the numbers of V. parahaemolyticus tdh and trh strains were low, with just 3/215 Pacific oyster samples carrying the tdh gene. V. parahaemolyticus organisms carrying tdh and trh were not detected in South Island samples, and V. parahaemolyticus was detected in just 1/21 dredge oyster and 2/16 mussel samples. Numbers of V. parahaemolyticus organisms increased when seawater temperatures were high, the season when most commercial shellfish-growing areas are not harvested. The numbers of V. parahaemolyticus organisms in samples exceeded 1,000 MPN/g only when the seawater temperatures exceeded 19°C, so this environmental parameter could be used as a trigger warning of potential hazard. There is some evidence that the total V. parahaemolyticus numbers increased compared with those reported from a previous 1981 to 1984 study, but the analytical methods differed significantly.

Impact of seafood regulations for Vibrio parahaemolyticus infection and verification by analyses of seafood contamination and infection

Consumption of seafood contaminated with Vibrio parahaemolyticus causes foodborne infections, which are on the rise owing to increased consumption of raw seafood in Asia, Europe, North America, and other regions. V. parahaemolyticus infections have been common in Japan since the 1960s. Following an epidemic in 1997, the Japanese Ministry of Health, Labour, and Welfare instituted regulations for seafood in 1999, which appear to be reducing V. parahaemolyticus infections. In this review, we describe the scientific findings for these regulations. Analyses of the V. parahaemolyticus serotypes and isolate characteristics in samples from infected patients and contaminated seafood are discussed. In addition, based on the results of a survey, we show that new food safety regulations have led to improvements in food hygiene at many seafood retail shops, food service facilities, and restaurants. This example from Japan could be of immense help to control foodborne infections in other countries.