Edible Shellfish Research Articles

Assessment of Heavy Metal (Zinc, Copper, Lead and Cadmium) Contamination in Common Edible Shellfish Species of the Hooghly River and Sunderbans, India

The content of four heavy metals (Zinc, Copper, Lead and Cadmium) in muscles of three shell fish species - prawns -Penaeus monodon and Penaeus indicus and crabs-Scylla serrata, the most prime shellfish food resources of human in the domestic and international market were studied at four stations in the estuarine belt near Bay-of-Bengal which receives wastes of various types from industries and various anthropogenic activities. The samples were digested by acid digestion. The metal contents were quantified using an AAS (Atomic absorption spectrophotometer). The distribution of trace metals accumulated in the muscle tissues of the above mentioned species was in the order- Zn > Cu> Pb> Cd. In the present study, levels of Zinc in the shell fishes ranged from 07.44±0.65 to 128.10 ±2.96 ; Cu ranged from 5 ±0.15 to 99.14 ±1.31; Pb varied from 1.67± 0.14 to 23.99 ± 0.79 and Cd ranged from 1.29± 0.35 to 7.09 ± 0.80.The concentration of the four metals exhibited spatial variation as station 1 >station 2 > station 3 > station 4, which could be a reflection of different bioavailability of metal concentrations in the water body at different stations. The results obtained showed that the metal concentrations in most of the cases were above the threshold value recommended by WHO. Metals such as Cu, Zn, Pb, Cd, can affect various aquatic organisms as well as human being either directly or indirectly as they can enter into the food chain and may be biomagnified at higher trophic levels which is one of the top concerns for human health. Essential heavy metals such as Zinc and Copper are relatively less harmful at low concentration while non-essential metals such as Cd and Pb are highly toxic even at low concentrations.

Bioaccumulation of natural radionuclides in edible molluscs and associated risk from the Ashtamudi Estuary, situated in a high background natural radiation zone (HBNRA), Kerala, southwest coast of India

The study investigated various natural radionuclides, including 238U, 232Th, 210Po, and 210Pb, in edible molluscan species collected from different zones of the Ashtamudi estuary. Physicochemical and sedimentological factors played crucial roles in influencing the distribution of radionuclides in water and sediments. Notably, bivalve species, particularly those from the Cyrenidae family, exhibited significant bioaccumulation of 210Po (up to 432.8 Bq kg−1) and 210Pb (up to 121.3 Bq kg−1), with Zone VI recording the highest biological concentration factor (BCF) and biological sediment accumulation factor (BSAF). The calculated effective dose for humans consuming bivalve meat was moderate, falling above the lower end of the ICRP range of 1 mSv y−1 but well below the upper limit of 20 mSv y−1 for existing elevated radiation zones. The intake of radioactivity from some bivalves corresponded to a cancer risk of approximately 3.2 × 10−2 (total mortality + morbidity), exceeding the acceptable risk threshold reported by the USEPA. However, this level of exposure indicated that immediate action might not be necessary, especially if further dose reduction proved impractical, in line with the ICRP's approach to optimizing radiation protection.

Edible Mollusks and Mysterious Mr Lovell

Edible Mollusks and Mysterious Mr Lovell

Detection of Microplastics and Heavy Metals in Famous Edible Molluscs in Can Gio Biosphere Reserve of Vietnam

Can Gio, designated in 2000, is the first Biosphere Reserve of Vietnam. In recent years, local agriculture, tourism, households, nearby industrial zones, and maritime transport have released substances into rivers flowing through Can Gio Mangrove to the East Sea and transported into creatures. This study aims to investigate microplastics and heavy metals in the famous seafood of Can Gio. A Raman microscope was used to identify microplastics from the tissue of oysters, grease snails, and clams after enzymatic treatment with trypsin. Heavy metals were quantified with ICP-MS after acidic treatment. As a result, microplastics were found in almost all samples, even up to 10 in a random individual of bivalve. Fibers dominated, especially from 30 to 150 µm long. The metal with the highest content was zinc, followed by copper, especially in oysters. Non-essential metals were also present in the soft tissue in the order As > Pb > Cd. The accumulation of metals in Can Gio’s molluscs was generally lower than in other regions and still in the allowed range for consumption of Vietnamese Standard. Although there have not been any Vietnamese regulations on the permissible level of microplastics for consumption, regular seafood intake will increase the risk of chronic poisoning and unknown disorders caused by the accumulation of microplastics and heavy metals.

Identifikasi mikroplastik pada anadara antiquata di pesisir desa Garassikang kabupaten Jeneponto

Microplastics are small particles <5 mm in size that come from plastic waste. The large amount of plastic waste produced every day, most of which is thrown into the sea, means that the presence of microplastics continues to increase and is widespread almost throughout the sea surface, including Jeneponto Regency. This is very risky for contamination of feather shellfish which are often consumed by local people, so it is very dangerous for health. Therefore, it is necessary to identify microplastics in feather shellfish in Garassikang Village. Aim to determine the characteristics of microplastics in feather clams found on the coast of Garassikang Village, Jeneponto Regency in 2023. This type of quantitative research uses a descriptive approach with laboratory tests. The population is all edible shellfish obtained directly in the coastal waters of Garassikang Village, Jeneponto Regency, with a total sample of 15 feather shellfish obtained using a purposive sampling technique. The average abundance of microplastics in feather clams was 512.53 particles/kg with a microplastic size of 0.027 mm - 6,800 mm. There are 2 types of microplastics found, namely fibers and fragments, and there are 3 types of microplastic colors, namely blue, red and transparent. There are microplastics in shellfish found on the coast of Garassikang village. Of the 15 shellfish samples, 12 shellfish contained microplastics, this needs to be investigated in more depth regarding how dangerous exposure to microplastics is to human health using the FTIR test.

Snail Shell Waste Threat to Sustainability and Circular Economy: Novel Application in Food Industries

Effective waste management has become an urgent societal challenge. Food waste is made up of items meant for human consumption that are lost, polluted, disposed of, or deteriorated; the reutilization of shells from mollusk waste is a severe problem in terms of environmental protection and the development of the circular economy. The properties of waste shells are presented and discussed, including their biological–natural origin and high calcium carbonate content. This could add social and innovation focus on shell waste management, getting a non-toxic, eco-sustainable, low-cost, biodegradable supplement to invest in. Furthermore, it has the potential to support the circular economy approach by creating a closed system that minimizes the use of natural resources and environmental contamination. This review explores edible mollusk shell waste sources and functional properties of inorganic components of snail shell waste like minerals and active substances like chitin, chitosan, and calcium carbonate and attempts to carry out a comprehensive analysis of the scientific literature published over the last 20 years, elucidating prominent patterns in the utilization of shell waste in food application industry, as additives and supplements development to promote both human and animal health.

Distribution of Commercially Important Edible Mollusc (Bivalvia and Gastropoda) from Six Districts of Terengganu, Malaysia

Terengganu has a large coastal and wetland area where it provides habitat for edible mollusc. The edible molluscs are one of the most important sources of animal protein for the local communities. The distribution of edible molluscs was studied in six districts of the Terengganu coastal waters between August 2020 and March 2022. In each district, samples were purchased from the wet market, fishing villages and roadside outlets every four months interval. A total of 1,043 individuals was observed and 23 species of edible molluscs were recorded from six districts of Terengganu representing 11 families. Bivalves were found to be dominated by 14 species from seven families. The family Cyrenidae (bivalve) was widespread in five districts where Geloina expansa, was recorded in almost all districts. Meanwhile, for gastropods, nine species from four families were found where Ellobiidae (gastropod) was dominant and the most common gastropod species was Faunus ater, which was found in four locations in Terengganu. These species have great commercial value in Terengganu districts as they are sought extensively as food by the locals and also represent one of their sources of financial survival, especially for those living near to coastal areas. This baseline study could serve as a future indicator for the sustainable management of fisheries resources and for further ecological studies.

β‐Chitin and chitosan from waste shells of edible mollusks as a functional ingredient

AbstractThe marine food‐processing industries were producing large quantities of shell wastes as a discard. Currently, this waste material was underutilized and leads to the landfill as a significant environmental issue. The outer shells or exoskeletons of mollusks serve as the best source of chitin. Three different allomorphs of chitin (γ, β, and γ) were extracted from different species of crustaceans, mollusks, and fungi. β‐Allomorphs predominantly exist in the shells of mollusks. β‐Chitin and its deacetylated product chitosan has been utilized for its special characteristic features, including biocompatibility, environmental friendly, and nontoxic properties. The extraction of β‐chitin and chitosan from the mollusk shell waste were evaluated in this work. Hence, this review aims to explore edible mollusk shell waste sources and its suitable extraction techniques, characterizations, and functional properties of mollusk‐based β‐chitin and chitosan. Further, the genetic pathway of synthesizing mollusk chitin was discussed. The entire life cycle assessment with techno‐economic aspects were extrapolated to study the bottlenecks and tangible solution for the industrial upscaling of obtaining β‐chitin and chitosan from the edible mollusk shell waste have been reviewed herein.

A sandwich ELISA for the detection of mollusks and mollusk products.

Mollusks are a major allergenic food under the food allergen regulations of many countries and must be declared on food products to reduce the risk of allergic reactions. However, a reliable immunoassay for detecting edible mollusks (cephalopods, gastropods, and bivalves) has not been reported. In this study, the developed sandwich enzyme-linked immunosorbent assay (sELISA) detected 32 edible mollusk species in raw and heated without cross-reaction with non-mollusk species. The detection limits of the assay were 0.1ppm for heated mollusks and 0.1-0.5ppm for raw mollusks, depending on the mollusk species tested. The inter-assay and intra-assay coefficients of variation (CVs) were≤14.83 and≤8.11, respectively. The assay detected steamed, boiled, baked, fried, and autoclaved mollusk samples and all commercial mollusk products tested. In this study, we developed a mollusk-specific sELISA to protect people allergic to mollusks.

Monitoring and Genotyping of Norovirus in Bivalve Molluscan Shellfish from Northern Italian Seas (2018-2020).

Norovirus (NoV) is an enteric virus with foodborne transmission. Bivalve shellfish are a main source of infections and outbreaks. In Italy a voluntary based monitoring plan to check the safety of bivalve shellfish was set up at provincial level. This study describes the occurrence and distribution of NoV in the Northern Adriatic Sea and in the Ligurian Sea. From October 2018 to September 2020, 807 bivalve shellfish samples (n = 205 oysters, n = 182 mussels, n = 348 clams, n = 72 other bivalve shellfish) were tested by One-Step Retrotranscription Real-time polymerase chain reaction for NoV GI and GII and quantified according to the ISO 15216-2:2013 and ISO 15216-1:2017. Positive samples were further analyzed to determine genotype by sequencing of the ORF1/ORF2 junction of the viral genome. A total of 126 samples were positive for NoV, mussels, and oysters had the highest probability of being positive and positive samples were found mainly in the colder season. Of these samples, 46% were NoV GII, 13% NoV GI, and 40% carried both genogroups. Thirty-seven samples were typeable (GI n = 12 and GII n = 25) with GI samples belonging to four genotypes and GII samples belonging to five genotypes. GII.3 genotype was the most prevalent, followed by GII.4, particularly Sydney 2012 subtype, a leading cause of infections worldwide, was found in three oysters' and three clams' samples. The phylogenetic analysis revealed a high heterogeneity among the species that are scattered in several clusters. Considering the low infectious dose the overall presence of NoV in edible shellfish, particular those to be eaten raw or undercooked, is moderately high. The presence of genotypes frequently involved in human infections strengthens the need for ongoing monitoring, which should be extended at national level.

Efficacy of Molecular Identification Using DNA Barcoding Technique of Freshwater Edible Molluscs from Nagaland, India

Freshwater molluscs are widely utilized for food and medicine in many regions of the world. One such area in India is the northeast, where tribal and economically underdeveloped communities consume freshwater molluscs. Because they are an inexpensive source of protein and offer food security, livelihoods, and medicine, these molluscs are in great demand. In the present work, molecular identification and documentation of the edible gastropods of Nagaland is done. Throughout the twentieth century, identification was based on morphology and anatomy. However, the identification based on morphological structure is challenging due to the existence of cryptic species that shows similar morphology which can lead to erroneous identification of species. Freshwater molluscs shells are highly varied and exhibit convergence evolution and hence may not always accurately indicate systematic boundaries. Thus, DNA bar-coding is a potential method for taxonomic identification process that can mitigate this problem. It uses genetic markers such as cytochrome oxidase I (COI) gene, 16S rDNA and 18S rDNA. In the present study COI mitochondrial gene is used. A fragment of COI gene is sequenced and their DNA is compared to the existing sequences in the genomic library. The sequence is then submitted in NCBI to obtain accession number. A total of 7 species of edible freshwater molluscs belonging to two class bivalvia and gastropoda was collected from local fishery ponds, confined water bodies, rivers, streams, and were identified. The identified species with their accession number is as follows, Lamellidens marginalis (ON209524), Parreysia corrugata (OM074301), Indonaia subclatharata (OM075118), Indonaia caerulea (OM076974), Bellamaya bengalensis (OM056888), Paludomus sp (OM078498), Brotia costula (OM056887). The study provides substantial support for COI's effectiveness as a prime marker for DNA barcoding of Indian edible freshwater gastropods and bivalves.

Bioavailability and health risk assessment of Zn and Cd in edible tissues of two typical shellfish species using in vitro gastrointestinal digestion

Dynamic extraction of edible tissues of Jinjiang oyster (Crassostrea rivularis) and Flower clam (Paphia undulata) was conducted using a fully biomimetic digestion (in vitro) method. The impact of different cooking methods on the bioavailability of Zn and Cd in the edible shellfish tissues was analyzed, and the human health risk of Zn and Cd was evaluated. The results show that the gastric biomimetic extractions of Zn and Cd in unheated samples of C. rivularis and P. undulata were higher than those in the intestinal biomimetic extraction. The extraction patterns of cooked samples were consistent with those of raw samples. The bioavailability of Zn and Cd in cooked samples of C. rivularis was 94.9% and 82.5%, respectively, indicating increased Zn bioavailability but decreased Cd bioavailability compared to the raw samples. The bioavailability of Zn and Cd in cooked samples of P. undulata was 85.1% and 83.0%, respectively, both of which decreased compared to the raw samples. Consumption of C. rivularis can provide 21.0% to 34.2% of the daily required Zn intake, while consumption of P. undulata can provide 3.8% to 6.4%. The intake of Cd from both shellfish species is below the monthly tolerable intake recommended by FAO/WHO. Consuming cooked C. rivularis can increase the intake of Zn and decrease the intake of Cd.

Rapid determination of domoic acid in seafood by fluorescence polarization immunoassay using a portable analyzer

Monitoring phycotoxin accumulation in marine products such as edible shellfish is a regulatory requirement in many countries. Therefore, a simple and rapid onsite quantification method is sought. Herein, we present a fluorescence polarization immunoassay (FPIA), a well-known one-step immunoassay, using a portable fluorescence polarization analyzer for domoic acid (DA), widely referred to as the primary toxin of amnesic shellfish poisoning (ASP). To establish FPIA for DA, the matrix effect of methanol, which is widely used to extract DA from shellfish, on FPIA was investigated. To validate this method, we performed a spike recovery test using oysters containing DA at a concentration equivalent to the regulatory limits of North America and the European Union (20 mg/kg). The recovery rate was found to be 79.4–114.7%, which is equivalent to that of the commercially available enzyme-linked immunosorbent assay (ELISA). We expect that this FPIA system will enable the quantitative onsite analysis of DA and significantly contribute to the safety of marine products.Graphical

Structure and toxicity of AZA-59, an azaspiracid shellfish poisoning toxin produced by Azadinium poporum (Dinophyceae)

To date, the putative shellfish toxin azaspiracid 59 (AZA-59) produced by Azadinium poporum (Dinophyceae) has been the only AZA found in isolates from the Pacific Northwest coast of the USA (Northeast Pacific Ocean). Anecdotal reports of sporadic diarrhetic shellfish poisoning-like illness, with the absence of DSP toxin or Vibrio contamination, led to efforts to look for other potential toxins, such as AZAs, in water and shellfish from the region. A. poporum was found in Puget Sound and the outer coast of Washington State, USA, and a novel AZA (putative AZA-59) was detected in low quantities in SPATT resins and shellfish. Here, an A. poporum strain from Puget Sound was mass-cultured and AZA-59 was subsequently purified and structurally characterized. In vitro cytotoxicity of AZA-59 towards Jurkat T lymphocytes and acute intraperitoneal toxicity in mice in comparison to AZA-1 allowed the derivation of a provisional toxicity equivalency factor of 0.8 for AZA-59. Quantification of AZA-59 using ELISA and LC-MS/MS yielded reasonable quantitative results when AZA-1 was used as an external reference standard. This study assesses the toxic potency of AZA-59 and will inform guidelines for its potential monitoring in case of increasing toxin levels in edible shellfish.

Value Chain for Non-Indigenous Bivalves in Greece: A Preliminary Survey for the Pearl Oyster Pinctada imbricata radiata

The present study investigates through an integrated survey, for the first time in Greek shellfish market, the marketing distribution towards a new edible shellfish product that of the non-indigenous pearl oyster Pinctada imbricata radiata. The survey conducted through personal interviews on sector entrepreneurs/staff of the supply (i.e., shellfish producers, wholesalers, fishmongers, owners of restaurants). Internet-based quantitative research was also conducted to explore the market supply of the pearl oyster covering all nine regional units of Greece. The market for pearl oyster seems to be there as a substitute of the major commercial species in seasons of shortages. There is a specimen mislabeling throughout Greece, thus, extraction of significant information about the market supply of pearl oyster is deficient. Further knowledge on the bivalve shellfish value chain is needed, to define how the wild and the farmed species (mussels) interact in the market and in the distribution channels, toward a product-easy to use in the supply chain and friendly to the consumer. Findings also raises additional concerns as a priority for conservation, and the current practices do not satisfy the Common Fisheries Policy in terms of traceability.

Habitual feeding patterns impact polystyrene microplastic abundance and potential toxicity in edible benthic mollusks

That increasing microplastics (MPs, <5 mm) eventually end up in the sediment which may become a growing menace to diverse benthic lives is worthy of attention. In this experiment, three edible mollusks including one deposit-feeding gastropod (Bullacta exarate) and two filter-feeding bivalves (Cyclina sinensis and Mactra veneriformis) were exposed to polystyrene microplastic (PS-MP) for 7 days and depurated for 3 days. PS-MP numbers in the digestive system and non-digestive system, digestive enzymes, oxidative stress indexes, and a neurotoxicity index of three mollusks were determined at day 0, 3, 7, 8 and 10. After seven-day exposure, the PS-MP were found in all three mollusks' digestive and non-digestive systems. And PS-MP in M. veneriformis (9.57 ± 2.19 items/individual) was significantly higher than those in C. sinensis (3.00 ± 2.16 items/individual) and B. exarate (0.83 ± 1.07 items/individual) at day 7. Three-day depuration could remove most of the PS-MP in the mollusks, and higher PS-MP clearance rates were found in filter-feeding C. sinensis (77.78 %) and M. veneriformis (82.59 %) compared to surface deposit-feeding B. exarate (50.00 %). The digestive enzymes of B. exarate significantly reacted to PS-MP exposure, while oxidative responses were found in C. sinensis. After three-day depuration, the changes of digestive enzymes and the oxidative states were fixed, but neurotoxicity induced by PS-MP was not recoverable. Besides, it is noteworthy that changes of digestive enzymes and acetylcholinesterase are related to feeding patterns.

Characterization of a novel polysaccharide from Arca subcrenata and its immunoregulatory activities in vitro and in vivo.

Arca subcrenata is an economical edible shellfish. A novel water-soluble α-D-glucan (ASPG-1) with a molecular weight of 2.56 × 106 Da was purified and characterized from A. subcrenata. Its structure was characterized as a repeating unit consisting of α-D-Glcp, (1 → 6)-α-D-Glcp and (1 → 4,6)-α-D-Glcp. ASPG-1 exerted potent immunoregulatory activity by promoting the viability of splenic lymphocytes. Moreover, it enhanced pinocytic capacity, and promoted the secretion of NO and cytokines in RAW264.7 cells. The immunomodulatory mechanism of ASPG-1 involved the activation of the TLR4-MAPK/Akt-NF-κB signaling pathway. ASPG-1 inhibited tumor growth in 4T1 breast cancer mice and its combination with doxorubicin increased antitumor efficacy. The ASPG-1 combination with DOX-treated group (64.8%) showed an improved tumor inhibition rate compared to that of the DOX-treated group (53.3%). The antitumor mechanism of ASPG-1 may involve an enhancement of the immune response of mice to tumors. These results indicated that ASPG-1 could be developed as a potential adjuvant in tumor immunotherapy.

Virulence and antimicrobial-resistance of shiga toxin-producing E. coli (STEC) Isolated from edible shellfish and its public health significance

Shiga toxin-producing E. coli (STEC) are an important cause of foodborne illness in humans with infections ranging from mild non-bloody diarrhea to bloody diarrhea (BD) and hemolytic uremic syndrome (HUS). This study aimed to investigate the distribution of STEC in shellfish from coastal shores of Lake Timsah in Ismailia Governorate, Egypt and its probable hazard to seafood consumers. Samples from the external surface and tissues of shrimp (n = 45), crabs (n = 45), and oysters (n = 45) batches were examined bacteriologically for the presence of STEC and tested for their antibiotic sensitivity. Moreover, occurrence of virulence genes was determined via detection of stx1, stx2 and eaeA genes using PCR. Overall, E. coli and presumptive STEC isolates (from CHROMagar) were identified from the surface (55.6 and 5.9%) and tissues (42.2 and 8.9%) of the examined shellfish batches, respectively. Five STEC isolates had been confirmed and found belonging to O26:H11, O125:H6, O146:H21, and O159 serogroups, those were 4 isolates from tissues of the three shellfish species and one isolate from the crab surface. The STEC isolates were multi-drug resistant, showing complete resistance to; penicillins, amoxycillin/clavulanic acid, colistin, fosfomycin, ceftriaxone, ciprofloxacin, and tetracycline, however, they were sensitive to gentamycin except O159 serogroup. The current study revealed low level of contamination of shellfish from coastal shores of Lake Timsah with STEC, however, it also highlights the extreme level of antimicrobial resistance exhibited by the presumptive and confirmed STEC isolates which is very hazardous for seafood consumers in the study area.

Larval cultivation of Periglypta chemnitzii based on microalgal dietary selection

Periglypta chemnitzii is an edible shellfish whose hardy nature makes it an ideal species for cultivation by aquaculture. The crucial factor determining whether a species is appropriate for aquaculture is successful breeding of the offspring. In this study, we gathered information regarding reproduction and larval cultivation of P. chemnitzii and assessed the suitability of different microalgae diets to serve as a baseline for the purpose of artificial breeding of the offspring. The embryonic and larval development, larval morphological changes, movement, and feeding behaviour of P. chemnitzii were observed under an optical microscope. Eight microalgal species (Chlorella vulgaris, Nannochloropsis oculata, Dunaliella salina, Platymonas subcordiformis, Pavlova viridis, Dicrateria zhanjianggensis, Isochrysis galbana, and Chaetoceros muelleri) were fed to the larvae at different ages to observe the ingestion and digestion by the larvae. Four kinds of single microalgae diets (C. vulgaris, P. subcordiformis, C. muelleri, and D. zhanjianggensis) and three kinds of mixed diets (P. subcordiformis + C. muelleri, P. subcordiformis + D. zhanjianggensis, and C. muelleri + D. zhanjianggensis) were fed to larvae respectively, and their growth and survival rate was monitored. We found that the fertilised eggs of P. chemnitzii hatched into D-shaped larvae after 11 h 26 min; the larvae then developed to the metamorphic stage at 6 days post hatch (dph) and began settlement at 7 dph. The larvae could ingest C. vulgaris, N. oculata, D. salina, P. viridis, D. zhanjianggensis, and I. galbana at 1 dph; some larvae could also ingest P. subcordiformis and C. muelleri at 2 dph. Notably, C. vulgaris and N. oculata were more difficult to digest. Further, mixed diets were more beneficial than single diets for larval growth and survival. In particular, the mixed combination of P. subcordiformis + C. muelleri afforded the fastest growth and the highest survival rate. In single diets, the fastest growth was attained with C. muelleri; whereas the highest survival rate was obtained with P. subcordiformis. Compared with other bivalve molluscs, the clam P. chemnitzii has larger embryos and larger-sized newly hatched larvae, and its embryonic development and planktonic larval stage are also shorter than that of other species. P. chemnitzii larvae were more likely to ingest the smaller, round-shaped microalgal species and digest the species without cell walls, and therefore, D. zhanjianggensis should be the first choice as an opening diet for P. chemnitzii larval cultivation, followed by a mixed microalgal diet of P. subcordiformis + C. muelleri from 3 dph onwards.

Survival and Genome Diversity of Vibrio parahaemolyticus Isolated from Edible Aquatic Animals

Vibrio parahaemolyticus can cause acute gastroenteritis, wound infection, and septicemia in humans. The waterborne bacterium is frequently isolated from aquatic products worldwide. Nevertheless, little information in genome evolution of V. parahaemolyticus isolated from aquatic animals is yet available. Here we overcome this limitation by specifying six V. parahaemolyticus isolates recovered from edible shellfish, fish, and crustacean. Most isolates with multiple resistance phenotypes grew optimally at 3% NaCl and pH 8.5. Draft genome sequences of the six V. parahaemolyticus isolates (4,937,042 bp to 5,067,778 bp) were determined using the Illumina Hiseq × 10 sequencing platform. Comparative genomic analyses revealed 4622 to 4791 predicted protein-encoding genes, of which 1064 to 1107 were of unknown function. Various mobile genetic elements (MGEs) were identified in the V. parahaemolyticus genomes, including genome islands (n = 5 to 9), prophage gene clusters (n = 0 to 2), integrons (n = 1 to 11), and insertion sequences (n = 0 to 3). A number of antibiotic-resistant (n = 17 to 20), virulence-associated (n = 77 to 79), and strain-specific (n = 131 to 287) genes were also identified, indicating possible horizontal gene transfer via the MGEs and considerable genome variation in the V. parahaemolyticus isolates. Altogether, the results of this study fill prior gaps in our knowledge of the genome evolution of V. parahaemolyticus, as isolated from edible aquatic animals.