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This paper reviews recent literature on the abundance and distribution of faecal indicator bacteria and pathogens in shellfish production areas in the state of Santa Catarina, on the subtropical coast of Brazil. This state supplies > 95% of the national production of shellfish. Microbiological monitoring data were mapped using GIS and the results compared with those from other countries. Coastal human population is the main predictive parameter for faecal bacteria in the production areas. Temporal variations of the bacteria can also be predicted by solar radiation and rainfall. The prevalence of pathogens such as hepatitis A virus, human norovirus, Salmonella spp. and Vibrio spp. does not differ substantially from that in developed countries. The information reported here can be used to inform development of microbiological risk profiles for shellfish production areas., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Norovirus contamination of oysters is the lead cause of non-bacterial gastroenteritis and a significant food safety concern for the oyster industry. Here, norovirus reduction from Pacific oysters (Crassostrea gigas), contaminated in the marine environment, was studied in laboratory depuration trials and in two commercial settings. Norovirus concentrations were measured in oyster digestive tissue before, during and post-depuration using the ISO 15216-1 quantitative real-time RT-PCR method. Results of the laboratory-based studies demonstrate that statistically significant reductions of up to 74% of the initial norovirus GII concentration was achieved after 3 days at 17-21 °C and after 4 days at 11-15 °C, compared to 44% reduction at 7-9 °C. In many trials norovirus GII concentrations were reduced to levels below 100 genome copies per gram (gcg -1 ; limit of quantitation; LOQ). Virus reduction was also assessed in commercial depuration systems, routinely used by two Irish oyster producers. Up to 68% reduction was recorded for norovirus GI and up to 90% for norovirus GII reducing the geometric mean virus concentration close to or below the LOQ. In both commercial settings there was a significant difference between the levels of reduction of norovirus GI compared to GII (p < 0.05). Additionally, the ability to reduce the norovirus concentration in oysters to < LOQ differed when contaminated with concentrations below and above 1000 gcg -1 . These results indicate that depuration, carried out at elevated (> 11 °C) water temperatures for at least 3 days, can reduce the concentration of norovirus in oysters and therefore consumer exposure providing a practical risk management tool for the shellfish industry.

Oysters hold a unique place within the field of aquaculture as one of the only organisms that is regularly shipped live to be consumed whole and raw. The microbiota of oysters is capable of adapting to a wide range of environmental conditions within their dynamic estuarine environments; however, human aquaculture practices can challenge the resilience of this microbial community. Several discrete stages in oyster cultivation and market processing can cause disruption to the oyster microbiota, thus increasing the possibility of proliferation by pathogens and spoilage bacteria. These same pressure points offer the opportunity for the application of probiotics to help decrease disease occurrence in stocks, improve product yields, minimize the risk of shellfish poisoning, and increase product shelf life. This review provides a summary of the current knowledge on oyster microbiota, the impact of aquaculture upon this community, and the current status of oyster probiotic development. In response to this biotechnological gap, the authors highlight opportunities of highest potential impact within the aquaculture pipeline and propose a strategy for oyster-specific probiotic candidate development.

Contamination of bivalve shellfish, particularly oysters, with norovirus is recognised as a significant food safety risk. Methods for quantification of norovirus in oysters using the quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR) are well established, and various studies using RT-qPCR have detected norovirus in a considerable proportion of oyster samples, both in the UK and elsewhere. However, RT-qPCR detects viral genome, and by its nature is unable to discriminate between positive results caused by infectious viruses and those caused by non-infectious remnants including damaged virus particles and naked RNA. As a result, a number of alternative or complementary approaches to RT-qPCR testing have been proposed, including the use of infectious viral indicator organisms, most frequently F-specific RNA bacteriophage (F-RNA phage). In this study, we investigated the relationships between F-RNA phage and norovirus in digestive tissues from two sets of oyster samples, one randomly collected at retail (630 samples), and one linked to suspected norovirus illness outbreaks (nine samples). A positive association and correlation between PCR-detectable levels of genogroup II F-RNA bacteriophage (associated with human faecal contamination) and norovirus was found in both sets of samples, with more samples positive for genogroup II phage, at generally higher levels than norovirus. Levels of both viruses were higher in outbreak-related than retail samples. Infectious F-RNA phage was detected in 47.8% of all retail samples, and for a subset of 224 samples where characterisation of phage was carried out, infectious GII phage was detected in 30.4%. Infectious GII phage was detected in all outbreak-related samples. Determination of infectivity ratios by comparing levels of PCR-detectable (copies/g) and infectious GII phage (pfu/g) revealed that in the majority of cases less than 10% of virus detected by RT-qPCR was infectious. Application of these ratios to estimate infectious norovirus levels indicated that while 77.8% of outbreak-related samples contained > 5 estimated infectious norovirus/g, only 13.7% of retail samples did. Use of a combination of levels of PCR-detectable norovirus and infectious F-RNA phage showed that while only 7.0% of retail samples contained both > 100 copies/g norovirus and > 10 pfu/g F-RNA phage, these combined levels were present in 77.8% of outbreak-related samples, and 75.9% of retail samples with > 5 estimated infectious norovirus/g. We therefore suggest that combining RT-qPCR testing with a test for infectious F-RNA phage has the potential to better estimate health risks, and to better predict the presence of infectious norovirus than RT-qPCR testing alone.

Two outbreaks of norovirus and acute gastroenteritis took place in Canada between November 2016 and April 2017. Both outbreaks were linked to oysters from British Columbia (BC) coastal waters. This paper describes the multi-agency investigations to identify the source and control the outbreak. Public health officials conducted interviews to determine case exposures. Traceback was conducted by collecting oyster tags from restaurants and analyzing them to determine the most common farms. Oyster samples were collected from case homes, restaurants, and harvest sites and tested for the presence of norovirus. Potential environmental pollution sources were investigated to identify the source of the outbreak. Four hundred and 49 cases were identified as part of the two outbreak waves. The oysters were traced to various geographically dispersed farms in BC coastal waters. Twelve farms were closed as a result of the investigations. No environmental pollution sources could be identified as the cause of the outbreak. Similarities in the timeframe, genotype, and geographic distribution of identified oyster farms indicate that they may have been one continuous event. Genotype data indicate that human sewage contamination was the likely cause of the outbreak, although no pollution source was identified.

Male-specific coliphages (MSCs) are currently used to assess the virologic quality of shellfish-growing waters and to assess the impact of sewage release or adverse weather events on bivalve shellfish. Since MSC can have either DNA or RNA genomes, and most research has been performed exclusively on RNA MSCs, persistence of M13, a DNA MSC, was evaluated for its persistence as a function of time and temperature within Eastern oysters (Crassostrea virginica). Oysters were individually exposed to seawater containing a total of 10 10 to 10 12 pfu of M13 for 24 h at 15 °C followed by maintenance in tanks with as many as 21 oysters in continuously UV-sterilized water for up to 6 weeks at either 7, 15, or 22 °C. Two trials for each temperature were performed combining three shucked oysters per time point which were assayed by tenfold serial dilution in triplicate. Initial contamination levels averaged 10 6.9 and ranged from 10 6.0 to 10 7.0 of M13. For oysters held for 3 weeks, log 10 reductions were 1.7, 3.8, and 4.2 log 10 at 7, 15, and 22 °C, respectively. Oysters held at 7 and 15 °C for 6 weeks showed average reductions of 3.6 and 5.1 log 10 , respectively, but still retained infectious M13. In total, this work shows that DNA MSC may decline within shellfish in a manner analogous to RNA MSCs.

This study investigated the influences of seawater to oyster ratio on depuration for decontaminating V. parahaemolyticus in raw oysters with a goal of identifying the proper ratio of oyster to seawater capable of improving the efficacy of the depuration process. The water to oyster ratios tested in this study ranged from 1.0 to 2.5 L of artificial seawater (ASW) per oyster (40 oysters in 40, 60, 80 and 100 L ASW). The depuration efficacy for purging V. parahaemolyticus from oysters was highest when we applied a 2:1, followed by 1.5:1, 2.5:1, and 1:1 L of ASW/oyster. Further studies of depuration with 2:1 L of ASW/oyster found that the concentration of V. parahaemolyticus in oysters decreased in a nonlinear manner. The depuration curve was fitted to a one phase decay model with a coefficient of determination (R 2 ) of 0.933. The time for a 3 log reduction was 1.75 days with a 95% confidence interval from 1.65 to 1.85 days, which meets the FDA's requirement of larger than a 3.0 log (MPN/g) reduction as a post-harvest process for V. parahaemolyticus control. After 4 days levels in all trials were <100 MPN/g meeting performance standards established by Japan and Canada. Furthermore, the time for a 3.52 log reduction was 3.17 days with a 95% confidence interval from 2.92 to 3.54 days but it took 5 days to reduce levels to <30 MPN/g, which satisfies FDA's requirement as a post-harvest control process (>3.52 log MPN/g reduction) for the purpose of making safety added labeling claims for V. parahaemolyticus., (Copyright © 2018. Published by Elsevier Ltd.)

Eastern oysters (Crassostrea virginica) from three locations along the Delaware Bay were surveyed monthly from May to October 2017 for levels of total Vibrio parahaemolyticus, pathogenic strains of V. parahaemolyticus and Vibrio vulnificus, and for strain-specific bacteriophages against vibrios (vibriophages). The objectives were to determine (a) whether vibriophages against known strains or serotypes of clinical and environmental vibrios were detectable in oysters from the Delaware Bay and (b) whether vibriophage presence or absence corresponded with Vibrio abundances in oysters. Host cells for phage assays included pathogenic V. parahaemolyticus serotypes O3:K6, O1:KUT (untypable) and O1:K1, as well as clinical and environmental strains of V. vulnificus. Vibriophages against some, but not all, pathogenic V. parahaemolyticus serotypes were readily detected in Delaware Bay oysters. In July, abundances of total and pathogenic V. parahaemolyticus at one site spiked to levels exceeding regulatory guidelines. Phages against three V. parahaemolyticus host serotypes were detected in these same oysters, but also in oysters with low V. parahaemolyticus levels. Serotype-specific vibriophage presence or absence did not correspond with abundances of total or pathogenic V. parahaemolyticus. Vibriophages were not detected against three V. vulnificus host strains, even though V. vulnificus were readily detectable in oyster tissues. Selected phage isolates against V. parahaemolyticus showed high host specificity. Transmission electron micrographs revealed that most isolates were ~ 60-nm diameter, non-tailed phages. In conclusion, vibriophages were detected against pandemic V. parahaemolyticus O3:K6 and O1:KUT, suggesting that phage monitoring in specific host cells may be a useful technique to assess public health risks from oyster consumption.

Organotin contamination in marine environment has been a public concern for many years due to its adverse impacts on biota and human health. This study investigated levels, distribution and health risks of six organotin compounds: tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT) and monophenyltin (MPhT) in commercial and wild oysters in China. The total organotin in commercial oysters ranged from 251 to 1949 ng Sn g -1 dw (dry weight) >. Two endocrine disruptors TBT and TPhT were detected in these samples with the highest level of 68.1 ± 20.1 ng Sn g -1 dw and 747 ± 7.3 ng Sn g -1 dw, respectively. For wild oysters, the concentrations of total organotins varied from 33.3 to 2671 ng Sn g -1 dw. Butyltins were dominated by TBT with the mean level of 26.1 ± 30.0 ng Sn·g -1 dw and showed no significant spatial variation between the southern and northern coastal zones (p > 0.05). However, compared with the north, phenyltin levels especially TPhT were much higher in the south coastline (246-1484 ng Sn·g -1 dw) due to the wider use of TPhT-based biocides in local mariculture and agriculture. Health risk assessment indicated that a daily exposure of TPhT-contaminated oysters (including commercial and wild ones) may pose adverse threats to human particularly children as the risk quotients (RQ) were higher than 1. Organotin contamination (e.g., TPhT) still occurs in the South China's coastal zones after the TBT ban, which deserves future research and effective measures to protect the marine ecosystem and human health., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Increased consumption and improper disposal of prescription medication, such as beta (β)-blockers, contribute to their introduction into waterways and may pose threats to non-target aquatic organisms. There has been rising concern about the impacts of these prescription drugs on coastal ecosystems, especially because wastewater treatment plants are not designed to eliminate them from the discharge. Few studies have characterized the sublethal effects of β-blocker exposures in marine invertebrates. The overall aim of our research is to identify cellular responses of two commercially important filter-feeding marine bivalves, hard clams (Mercenaria mercenaria) and Eastern oysters (Crassostrea virginica), upon exposures to two β-blocker drugs, propranolol and metoprolol. In vitro exposures with bivalve digestive gland and gill tissues were conducted where tissues were separately exposed to each drug for 24 h. Tissue samples were analyzed for cellular damage (lysosomal membrane destabilization and lipid peroxidation), total antioxidant capacity, and glutathione-s-transferase activity. Elevated damage and changes in enzyme activities were noted in the exposed tissues at environmentally relevant concentrations. Differences in species and tissue sensitivities and responses to exposures were also observed. These studies enhance our understanding of the potential impacts of prescription medication on coastal organisms. Additionally, this work demonstrates that filter-feeders may serve as good model organisms to examine the effects of unintended environmental exposures to β-blockers. These studies are part of our ongoing work aimed at evaluation of sublethal biomarkers of pharmaceutical exposures and identification of key events that can contribute to the development of adverse outcome pathways (AOPs)., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Contamination of bivalve shellfish, particularly oysters, with norovirus is recognised as a food safety risk and a potential contributor to the overall burden of gastroenteritis in the community. The United Kingdom (UK) has comprehensive national baseline data on the prevalence, levels, and seasonality of norovirus in oysters in production areas resulting from a previous two-year study (2009-2011). However, previously, data on final product as sold to the consumer have been lacking. As part of a wider project to establish the overall burden of foodborne norovirus in the UK, this study aimed to address this data gap. A one-year survey of oysters collected from the point-of-sale to the consumer was carried out from March 2015 to March 2016. A total of 630 samples, originating in five different European Union Member States, were collected from 21 regions across the UK using a randomised sampling plan, and tested for norovirus using a method compliant with ISO 15216-1, in addition to Escherichia coli as the statutory indicator of hygiene status. As in the previous production area study, norovirus RNA was detected in a high proportion of samples (68.7%), with a strong winter seasonality noted. Some statistically significant differences in prevalences and levels in oysters from different countries were noted, with samples originating in the Netherlands showing lower prevalences and levels than those from either the UK or Ireland. Overall, levels detected in positive samples were considerably lower than seen previously. Investigation of potential contributing factors to this pattern of results was carried out. Application of normalisation factors to the data from the two studies based on both the numbers of norovirus illness reports received by national surveillance systems, and the national average environmental temperatures during the two study periods resulted in a much closer agreement between the two data sets, with the notably different numbers of illness reports making the major contribution to the differences observed in norovirus levels in oysters. The large majority of samples (76.5%) contained no detectable E. coli; however, in a small number of samples (2.4%) levels above the statutory end product standard (230 MPN/100 g) were detected. This study both revealed the high prevalence of norovirus RNA in oysters directly available to the UK consumer, despite the high level of compliance with the existing E. coli-based health standards, while also highlighting the difficulty in comparing the results of surveys carried out in different time periods, due to variability in risk factors.

Oysters contaminated with norovirus present a significant public health risk when consumed raw. In this study, norovirus genome copy concentrations were determined in Pacific oysters (Magallana gigas) harvested from a sewage-impacted production site and then subjected to site-specific management procedures. These procedures consisted of relocation of oysters to an alternative production area during the norovirus high-risk winter periods (November to March) followed by an extended depuration (self-purification) under controlled temperature conditions. Significant differences in norovirus RNA concentrations were demonstrated at each point in the management process. Thirty-one percent of oyster samples from the main harvest area (Site 1) contained norovirus concentrations > 500 genome copies/g and 29% contained norovirus concentrations < 100 genome copies/g. By contrast, no oyster sample from the alternative harvest area (Site 2) or following depuration contained norovirus concentrations > 500 genome copies/g. In addition, 60 and 88% of oysters samples contained norovirus concentrations < 100 genome copies/g in oysters sampled from Site 2 and following depuration, respectively. These data demonstrate that site-specific management processes, supported by norovirus monitoring, can be an effective strategy to reduce, but not eliminate, consumer exposure to norovirus genome copies.

Vibrio parahaemolyticus is a major pathogen that is mainly associated with seafood and is a global concern of food safety. With high prevalence of contamination in food, efficient strategy is needed to decontaminate those contaminated foods and control the emergence of vibriosis. In the present study, a V. parahaemolyticus-specific phage vB&#95;VpaS&#95;OMN (designated as phage OMN) was isolated from oyster. Phage OMN had good pH (5-9) and temperature tolerance (<50 °C). Phage OMN exhibited broad host range against isolates of V. parahaemolyticus (20/31). After treatment with phage OMN in the liquid condition for 7 h, the number of V. parahaemolyticus was reduced significantly compared to control treatment. When phage OMN was applied to oyster samples for 48 and 72 h, 90% and 99%, respectively, of V. parahaemolyticus was inactivated on Oyster meat surface. Sequence analysis showed that phage OMN had a 42.202 bp genome and revealed about 59.04% homology with Cronobacter phage vB&#95;CsaP&#95;Ss1. Only 10 CDSs can be predicted based on the GenBank database, while 42% of the CDSs were unique to OMN and had no known function, indicating that phage OMN is a new lytic phage. Fully understanding of the function for the phage genes and the properties of the phage is important for the development of strategies to control V. parahaemolyticus contamination in oysters and disease in aquaculture., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This paper reports a study of norovirus (NoV) GII distribution and persistence in Sydney rock oysters (SRO) (Saccostrea glomerata) located in an estuary after a pump station sewage overflow. SRO were strategically placed at six sites spanning the length of the estuary from the pump station to the sea. The spatial and temporal distribution of NoV, hepatitis A virus (HAV) and Escherichia coli (E. coli) in oysters was mapped after the contamination event. NoV GI and GII, HAV and E. coli were quantified for up to 48 days in oysters placed at six sites ranging from 0.05 to 8.20 km from the sewage overflow. NoV GII was detected up to 5.29 km downstream and persisted in oysters for 42 days at the site closest to the overflow. NoV GII concentrations decreased significantly over time; a reduction rate of 8.5% per day was observed in oysters (p < 0.001). NoV GII concentrations decreased significantly as a function of distance at a rate of 5.8% per km (p < 0.001) and the decline in E. coli concentration with distance was 20.1% per km (p < 0.001). HAV and NoV GI were not detected. A comparison of NoV GII reduction rates from oysters over time, as observed in this study and other published research, collectively suggest that GII reduction rates from oysters may be broadly similar, regardless of environmental conditions, oyster species and genotype.

Male-specific bacteriophages have been proposed as human enteric virus indicators for shellfish. In this study, Eastern oysters (Crassostrea virginica) were individually exposed to 5.6 × 10 10 PFU of MS-2 for 48 h at 15 °C followed by collective maintenance in continuously UV-sterilized seawater for 0-6 weeks at either 7, 15, or 24 °C. Initial contamination levels of MS-2 were >6 log PFU. Assessment of weekly declines of viable MS-2 indicated that cooler temperatures dramatically enhanced the persistence of MS-2 within oyster tissues. At 3 weeks, the average log PFU reductions for MS-2 within oysters were 2.28, 2.90, and 4.57 for oysters held at 7, 15, and 24 °C, respectively. Fitting temporal survival data with linear and nonlinear Weibull models indicated that the Weibull model best fit the observed reductions. In total, these data can serve as a guideline for regulatory agencies regarding the influence of water temperature on indicator phage after episodic sewage exposure.

Vibrio parahaemolyticus and Vibrio vulnificus are naturally occurring estuarine bacteria and are the leading causes of seafood-associated infections and mortality in the United States. Though multiple-antibiotic-resistant V. parahaemolyticus and V. vulnificus strains have been reported, resistance patterns in vibrios are not as well documented as those of other foodborne bacterial pathogens. Salinity relaying (SR) is a postharvest processing (PHP) treatment to reduce the abundances of these pathogens in shellfish harvested during the warmer months. The purpose of this study was to evaluate the antimicrobial susceptibility (AMS), pathogenicity, and genetic profiles of V. parahaemolyticus and V. vulnificus recovered from oysters during an oyster relay study. Isolates ( V. parahaemolyticus [ n = 296] and V. vulnificus [ n = 94]) were recovered from oysters before and during the 21-day relaying study to detect virulence genes ( tdh and trh ) and genes correlated with virulence ( vcgC ) using multiplex quantitative PCR (qPCR). AMS to 20 different antibiotics was investigated using microbroth dilution, and pulsed-field gel electrophoresis (PFGE) was used to study the genetic profiles of the isolates. Twenty percent of V. vulnificus isolates were vcgC + , while 1 and 2% of V. parahaemolyticus were tdh + and trh + , respectively. More than 77% of the V. vulnificus isolates and 30% of the V. parahaemolyticus isolates were resistant to at least one antimicrobial. Forty-eight percent of V. vulnificus and 8% of V. parahaemolyticus isolates were resistant to two or more antimicrobials. All isolates demonstrated a high genetic diversity, even among those isolated from the same site and having a similar AMS profile. No significant effects of the relaying process on AMS, virulence genes, or PFGE profiles of V. vulnificus and V. parahaemolyticus isolated from oysters during this study indicated that more than 48% of IMPORTANCE Analysis of the antibiotic resistance profiles of V. vulnificus and V. parahaemolyticus isolated from oysters during this study indicated that more than 48% of V. vulnificus isolates were resistant to two or more antimicrobials, including those recommended by the CDC for treating Vibrio infections. Also, the V. parahaemolyticus isolates showed high MICs for some of the Vibrio infection treatment antibiotics. Monitoring of AMS profiles of this bacterium is important to ensure optimal treatment of infections and improve food safety. Our study showed no significant differences in the AMS profiles of V. vulnificus = 0.23) isolated from the oysters collected before versus after relaying. This suggests that the salinity of the relaying sites did not affect the AMS profiles of the P isolates, although it did reduce the numbers of these bacteria in oysters (S. Parveen et al., J Food Sci 82:484-491, 2017, https://doi.org/10.1111/1750-3841.13584).V. parahaemolyticus ( P = 0.23) isolated from the oysters collected before versus after relaying. This suggests that the salinity of the relaying sites did not affect the AMS profiles of the Vibrio isolates, although it did reduce the numbers of these bacteria in oysters (S. Parveen et al., J Food Sci 82:484-491, 2017, https://doi.org/10.1111/1750-3841.13584)., (Copyright © 2018 American Society for Microbiology.)

Norovirus (NoV) contamination of filter feeding bivalve shellfish is a well-recognised human health threat when shellfish are grown in sewage polluted waters. To date, the identification of high risk zones around sewage discharges in shellfish production areas (SPAs) has not been based on NoV data. This study utilised molecular methods for NoV analysis, combined with hydrographic studies, to determine the relationship between NoV concentrations in shellfish and sewage effluent dilution. Cages with mussels and oysters were placed at different distances downstream of sewage discharges in two coastal sites in England. The shellfish were tested for concentrations of NoV (genogroups I and II) and E. coli. Drogue tracking and dye tracing studies were conducted to quantify the dispersion and dilution of sewage effluent in the SPAs. Significant negative associations were found between both total concentrations of NoV (GI + GII) and E. coli and sewage effluent dilution in the SPAs. The total NoV concentrations predicted by the model at 300:1, 1000:1 and 5000:1 ratios of estuarine water to sewage effluent were 1200; 600; and 200 copies/g, respectively. The estimated area of NoV contamination varied according with local pollution source impacts and hydrographic characteristics. The results help to inform the derivation of sewage discharge buffer zones as a control measure for mitigating risk from human NoV contamination in SPAs., (Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.)

Monitoring of Vibrio vulnificus and V. parahaemolyticus abundance is pertinent due to the ability of these species to cause disease in humans through aquatic vectors. Previously, we performed a multiyear investigation tracking Vibrio spp. levels in five sites along the southeastern North Carolina coast. From February 2013 to October 2015, total V. vulnificus and V. parahaemolyticus abundance was measured in water, oysters and clams. In the current study, pathogenic subpopulations were identified in these isolates using molecular markers, revealing that 5.3% of V. vulnificus isolates possessed the virulence-correlated gene (vcgC), and 1.9% of V. parahaemolyticus isolates harbored one or both of the virulence-associated hemolysin genes (tdh and trh). Total V. parahaemolyticus abundance was not sufficient to predict the abundance of pathogenic subpopulations. Specifically, pathogenic V. parahaemolyticus isolates were more often isolated in cooler waters and were sometimes isolated when no other V. parahaemolyticus strains were detectable. Vibrio vulnificus clinical (C-) genotypes correlated with total V. vulnificus; however, salinity, water depth and total suspended solids influenced C- and E-genotypes differently. Lastly, we documented individual oysters harboring significantly higher V. vulnificus levels for which there was no ecological explanation, a phenomenon that deserves closer attention due to the potentially elevated health hazard associated with these 'hot' shellfish., (© FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

F-specific RNA bacteriophages (FRNAPH) have been used as indicators of environmental fecal pollution for many years. While FRNAPH subgroup I (FRNAPH-I) are not host specific, some FRNAPH-II and -III strains appear specific to human pollution. Because a close relationship has been observed between FRNAPH-II genome and human norovirus (NoV) in shellfish, and because FRNAPH infectivity can easily be investigated unlike that of NoV, the detection of human infectious FRNAPH could therefore provide a valuable tool for assessing viral risk. In this study, an integrated cell culture real-time RT-PCR method has been developed to investigate infectious FRNAPH subgroup prevalence in oysters. This rapid screening method appears more sensitive than E. coli or NoV genome detection, and allows an FRNAPH subgroup present in low concentrations (0.05 PFU/g of oyster) to be detected in the presence of another 1000 times more concentrated, without any dissection step. Its application to marketed oysters (n = 135) over a 1-year period has allowed to identify the winter peak classically described for NoV or FRNAPH accumulation. Infectious FRNAPH were detected in 34% of batches, and 7% were suspected of having a human origin. This approach may be helpful to evaluate oyster's depuration processes, based on an infectious viral parameter., (Published by Elsevier Ltd.)

A production area repeatedly implicated in oyster-related gastroenteritis in France was studied for several months over 2 years. Outbreaks and field samples were analyzed by undertaking triplicate extractions, followed by norovirus (NoV) detection using triplicate wells for genomic amplification. This approach allowed us to demonstrate that some variabilities can be observed for samples with a low level of contamination, but most samples analyzed gave reproducible results. At the first outbreak, implicated oysters were collected at the beginning of the contamination event, which was reflected by the higher NoV levels during the first month of the study. During the second year, NoV concentrations in samples implicated in outbreaks and collected from the production area were similar, confirming the failure of the shellfish depuration process. Contamination was detected mainly during winter-spring months, and a high prevalence of NoV GI contamination was observed. A half-life of 18 days was calculated from NoV concentrations detected in oysters during this study, showing a very slow decrease of the contamination in the production area. Preventing the contamination of coastal waters should be a priority.

This study examines the relationships between concentrations of human noroviruses (NoV) genogroups I (GI) and II (GII) and Escherichia coli monitored in oysters from 31 commercial harvesting areas on the coast of England and Wales from May 2009 to April 2011 and demographic, hydrometric, climatic and pollution source characteristics of upstream river catchments using multiple regression techniques. The predictive environmental factors for E. coli contamination in the oysters were rainfall (cumulative 7days before sampling) while the predictive factors for NoV (GI+GII) were water temperature, catchment area and the combined volume of continuous sewage discharges in the catchment. Oysters from cold waters (<5°C) had significantly higher NoV content than those from warmer waters (>10°C). The association with water temperature may be consequential on the seasonal prevalence of the virus in the community or linked with oyster metabolic function. In a group of 10 study sites, mean concentrations of NoV increased as the number of stormwater spills at those sites also increased. The results of this study could be used to evaluate the likely impact of sewerage infrastructure improvements in catchments at risk of NoV contamination and to help identify sites suitable for shellfish farming., (Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.)

Filter feeding shellfish can concentrate pathogenic bacteria, including Vibrio vulnificus and Vibrio parahaemolyticus, as much as 100-fold from the overlying water. These shellfish, especially clams and oysters, are often consumed raw, providing a route of entry for concentrated doses of pathogenic bacteria into the human body. The numbers of foodborne infections with these microbes are increasing, and a better understanding of the conditions that might trigger elevated concentrations of these bacteria in seafood is needed. In addition, if bacterial concentrations in water are correlated with those in shellfish, then sampling regimens could be simplified, as water samples can be more rapidly and easily obtained. After sampling of oysters and clams, either simultaneously or separately, for over 2 years, it was concluded that while Vibrio concentrations in oysters and water were related, this was not the case for levels in clams and water. When clams and oysters were collected simultaneously from the same site, the clams were found to have lower Vibrio levels than the oysters. Furthermore, the environmental parameters that were correlated with levels of Vibrio spp. in oysters and water were found to be quite different from those that were correlated with levels of Vibrio spp. in clams., Importance: This study shows that clams are a potential source of infection in North Carolina, especially for V. parahaemolyticus These findings also highlight the need for clam-specific environmental research to develop accurate Vibrio abundance models and to broaden the ecological understanding of clam-Vibrio interactions. This is especially relevant as foodborne Vibrio infections from clams are being reported., (Copyright © 2016 American Society for Microbiology.)

An acute gastroenteritis (AGE) outbreak was reported in May 2013 in Gyeonggi Province, South Korea. Eight students who had eaten breakfast on 21 May 2013 at a high-school restaurant exhibited AGE symptoms. Our case-control study showed that a strong association was observed between AGE symptoms and fermented oyster consumption. Virological studies also indicated that noroviruses (NoVs) were detected from both clinical samples and fermented oyster samples, and multiple different genotypes (genogroups GII.4, GII.11 and GII.14) of NoVs were present in both samples. The nucleotide sequence similarity between the strains found in the clinical samples and those in the fermented oysters was more than 99·5%. Therefore, to prevent further outbreaks, proper management of raw oysters is necessary and the food industry should be aware of the risk of viral gastroenteritis posed by fermented oysters contaminated with NoVs.

Human noroviruses are the leading cause of non-bacterial shellfish associated gastroenteritis. Here we report on the detection and characterization of norovirus (NoV) in shellfish associated outbreaks. Requests were received from state and federal officials for technical assistance in the analysis of shellfish for NoV and male specific coliphage (MSC; an enteric virus surrogate) during the years 2009 thru 2014. In outbreaks where NoV was detected, genogroup II (GII) levels ranged from 2.4 to 82.0 RT-qPCR U/g of digestive diverticula (DD) while NoV genogroup I (GI) levels ranged from 1.5 to 29.8 RT-qPCR U/g of DD. Murine norovirus extraction efficiencies ranged between 50 and 85%. MSC levels ranged from <6 to 80 PFU/100 g. Phylogenetic analysis of the outbreak sequences revealed strains clustering with GI.8, GI.4, GII.3, GII.4, GII.7, and GII.21. There was 100% homology between the shellfish and clinical strains occurring in 2 of 8 outbreaks. Known shellfish consumption data demonstrated probable infectious particles ingested as low as 12. These investigations demonstrate effective detection, quantification, and characterization of NoV in shellfish associated with illness., (Published by Elsevier Ltd.)

Molluscan shellfish can cause food borne diseases and here we investigated if addition of Vibrio-antagonising bacteria could reduce Vibrio vulnificus in model oyster systems and prevent its establishment in live animals. Phaeobacter inhibens, which produces an antibacterial compound, tropodithietic acid (TDA), inhibited V. vulnificus as did pure TDA (MIC of 1-3.9 μM). P. inhibens DSM 17395 (at 10(6) cfu/ml) eradicated 10(5) cfu/ml V. vulnificus CMCP6 (a rifampicin resistant variant) from a co-culture oyster model system (oyster juice) whereas the pathogen grew to 10(7) cfu/ml when co-cultured with a TDA negative Phaeobacter mutant. P. inhibens grew well in oyster juice to 10(8) CFU/ml and sterile filtered samples from these cultures were inhibitory to Vibrio spp. P. inhibens established itself in live European flat oysters (Ostrea edulis) and remained at 10(5) cfu/g for five days. However, the presence of P. inhibens could not prevent subsequently added V. vulnificus from entering the live animals, likely because of too low levels of the biocontrol strain. Whilst the oyster model studies provided indication that P. inhibens DSM 17395 could be a good candidate as biocontrol agent against V. vulnificus further optimization is need in the actual animal rearing situation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The purpose of the study was to determine the effect of high-hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin-conjugated magnetic beads (PGM-MBs) and viral RNA was quantified by real-time RT-PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log10 reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1- to 5-scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure-treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05)., (© 2015 Institute of Food Technologists®)

The Hong Kong oysters Crassostrea hongkongensis are widely farmed in the estuarine waters of Southern China, but they accumulate Cu and Zn to alarmingly high concentrations in the soft tissues. Health risks of seafood consumption are related to contaminants such as toxic metals which are bioaccessible to humans. In the present study, we investigated the oral bioaccessibility of five toxic metals (Ag, Pb, Cd, Cu and Zn) in contaminated oysters collected from different locations of a large estuary in southern China. In all oysters, total Zn concentration was the highest whereas total Pb concentration was the lowest. Among the five metals, Ag had the lowest oral bioaccessibility (38.9-60.8%), whereas Cu and Zn had the highest bioaccessibility (72.3-93.1%). Significant negative correlation was observed between metal bioaccessibility and metal concentration in the oysters for Ag, Cd, and Cu. We found that the oral bioaccessibility of the five metals was positively correlated with their trophically available metal fraction (TAM) in the oyster tissues, and negatively correlated with metal distribution in the cellular debris. Thus, metal partitioning in the TAM and cellular debris controlled the oral bioaccessibility to humans. Given the dependence of oral bioaccessibility on tissue metal contamination, bioaccessibility needs to be incorporated in the risk assessments of contaminated shellfish., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Oysters have a high commercial value but owing to their short shelf life are generally commercialized as raw material within very restricted market borders. A step-by-step optimization approach was used in this work to design ready-to-eat oyster packaging. In particular, six different steps were carried out in order to extend their shelf life., Results: The concentration of sodium alginate to realize a coating that was effective in terms of easy peeling and ability in preventing product dehydration was optimized. Coated oysters were packaged under different modified atmosphere (MAP) conditions to find the best MAP. Subsequently, to further promote product preservation, sodium acetate was selected as an effective antimicrobial agent to be applied by dipping treatment prior to coating. All preservation strategies singly tested were finally combined to assess the shelf life prolongation of ready-to-eat oysters., Conclusion: Dipping in sodium acetate (10 g L⁻¹), coating with sodium alginate (40 g L⁻¹) and packaging under MAP (0:75 O₂:CO₂) represent the best conditions to guarantee a significant shelf life extension to about 160 h compared with 57 h for unpackaged oysters., (© 2014 Society of Chemical Industry.)

US vibriosis rates have increased since 1996, and many Vibrio vulnificus infections are fatal. In April 2003, California implemented a regulation restricting the sale of raw oysters harvested from the Gulf of Mexico during April 1-October 31, unless they were processed to reduce V. vulnificus to nondetectable levels. We analyzed California cases of V. vulnificus infection before and after the regulation's implementation and compared case data with data from other states. The annual number of reported V. vulnificus infections and deaths in California with patient's sole exposure to raw oysters dropped from 0 to 6 cases and 0 to 5 deaths per year during 1991-2002, before implementation, to 0 during 2003-2010, after implementation (p = 0.0005 for both). In other states, median annual numbers of similar cases and deaths increased slightly after 2002. The data strongly suggest that the 2003 regulation led to a significant reduction in reported raw oyster-associated V. vulnificus illnesses and deaths.

A new selective and differential medium, Vibrio vulnificus X-Gal (VVX), was developed for direct enumeration of V. vulnificus (Vv) from oyster samples. This agar utilizes cellobiose and lactose as carbon sources, and the antibiotics colistin and polymyxin B as selective agents. Hydrolysis of 5-bromo-4-chloro-3-indolyl- beta-d-galactopyranoside (x-gal), used in the agar as a lactose analog, produces an insoluble blue dye that makes lactose positive colonies easily distinguishable from any non-lactose fermenting bacteria. Various bacterial species were spot plated onto thiosulfate-citrate-bile salts-sucrose agar (TCBS), and CHROMagar Vibrio, two vibrio-specific selective agars, non-selective agar, and VVX to compare selectivity of VVX to other widely used media. A V. vulnificus pure culture was serially diluted on VVX and non-selective agar to determine the VVX percent recovery. Water and oyster samples were spread plated on VVX agar and allowed to incubate for 16-18 h at 33 °C. Blue and white colonies from VVX agar were picked and screened by end point PCR for the Vv hemolysin vvhA. VVX agar showed a significant improvement over TCBS and CHROMagar at preventing non-target growth. There was an 87.5% recovery compared to non-selective plating and a 98% positivity rate of blue colonies picked from oyster tissue plating. The findings suggest that this new agar is a fast, distinctive, and accurate method for enumeration of V. vulnificus from the environment., (Copyright © 2013 Elsevier B.V. All rights reserved.)

An innovative approach to Post-Harvest Processing (PHP) of oysters is introduced focusing on the effects of supercritical carbon dioxide (scCO(2)) on bacterial contaminants trapped in the digestive system of oysters. Oysters were exposed to scCO(2) under two conditions: (1) 100 bar and 37 degrees C for 30 min and (2) 172 bar and 60 degrees C for 60 min. Using FDA standard guidelines for food analysis, variations in the Aerobic Plate Count (APC) were assessed. It was established that exposing oysters to CO(2) at 100 bar and 37 degrees C for 30 min and at 172 bar and 60 degrees C for 60 min induced 2-log and 3-log reductions in the APC respectively. The decrease in the microbial load as a result of treatment with scCO(2) was found to be significant (P=0.002). A release of adductor muscles from the shell was noted in oysters treated at 172 bar and 60 degrees C for 60 min; this was not the case for oysters treated at 100 bar and 37 degrees C for 30 min. A blind study allowing sensory analysis of treated vs. untreated oysters was also completed and no significant change in the physical appearance, smell, or texture was recorded. In this paper, we also report the effect of scCO(2) on several bacterial isolates, including a referenced ATCC strain of a non-pathogenic Vibrio (Vibrio fischeri) as well as several other bacterial isolates cultured from oyster' tissues and found to share biochemical features common to pathogenic Vibrio strains. A complete inactivation (minimum 7-log reduction) was achieved with these latter bacterial isolates. A 6-log reduction was observed with V. fischeri., (Copyright 2009 Elsevier B.V. All rights reserved.)

Per- and polyfluoroalkyl substances (PFAS) are known to bioaccumulate in aquatic organisms, such as shellfish, and have been linked to adverse human health outcomes. Increasing attention has been focused on method development for the detection of PFAS in various media; however, these methods are typically tedious, require high solvent volumes, and are time consuming. The present method used a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction approach and analysis by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) to detect 28 PFAS in Eastern oyster (Crassostrea virginica) tissue. This method was validated using limit of detection, limit of quantitation, and precision and accuracy studies. Limits of detection ranged from 0.2 to 5.8 ng g−1, limits of quantitation ranged from 0.66 to 19.2 ng g−1, and recoveries spanned 52.1–105.9% at the 100 ng mL−1 analyte level. Analysis of 12 unknown oyster composite samples revealed the detection of PFHxA, PFPeS, PFOA, PFHpA and PFOS and at least two compounds were detected in each oyster sample. This validated method proved to be an efficient and environmentally friendly sample preparation method for PFAS analysis in complex tissue media, such as oysters. [ABSTRACT FROM AUTHOR]

Crassostrea is the most farmed oyster genus worldwide and has significant economic and social impacts with environmental benefits. Hatchery oyster seed production is a highly costly phase, and a fluidized nursery system can help reduce this cost and reduce seed production time. The present study evaluated the survival and growth of two oyster species (Crassostrea gasar and Crassostrea gigas) in a fluidized bed bottle nursery system. With C. gasar, two experiments were performed; one tested three stocking densities and the other three bialgae diets. With C. gigas, one experiment with a bialgae and monoalgae in an initial bottle occupation of 8.8% produced more seeds per bottle, but an initial bottle occupation of 2.2% produced bigger seeds. Also, the experiment with C. gasar and with C. gigas tested diets did not affect seed survival, but the diets with bialgae I. galbana and N. oculate promoted more seed growth. The fluidized bed bottle nursery system developed for this study was adequate for the seeds of the oysters C. gasar and C. gigas in the nursery phase. [ABSTRACT FROM AUTHOR]

Objective: Oyster reefs across North America have declined precipitously over the past 140 years. In Washington State, Olympia oyster Ostrea lurida reefs historically provided water filtration and nearshore structural habitat for fishes and invertebrates, but this species is now functionally extinct across its historical range. In place of these naturally occurring reefs, shellfish farms consisting mainly of nonnative Pacific oysters Magallana gigas now occupy patches of nearshore habitat across Washington. These farms modify intertidal substrate by adding structural habitat via suspended oyster grow bags, predator exclusion nets, loose oyster beds, and other shellfish grow‐out gear. As interest and investment in shellfish aquaculture have expanded both locally and globally, so has interest in how these farms modify intertidal habitat and whether the complex structure created by the shellfish and shellfish growing gear provides ecosystem services that are comparable to those of unfarmed areas, such as mudflats and eelgrass meadows. Methods: In this study, we sought to quantify how shellfish farms are used as foraging habitat for several common nearshore species of fish and crabs in Puget Sound, Washington. We used direct observations of species‐specific behaviors from underwater video to model how habitat type affected observed foraging rates. Result: We obtained a total of 393 crab observations, 431 demersal fish observations, and 1856 pelagic fish observations across all seven farm sites. Several common species of pelagic fish (e.g., surfperch [Embiotocidae]) used aquaculture‐growing gear more frequently than unfarmed areas as foraging habitat, but Metacarcinus spp. crabs displayed higher foraging frequency in unfarmed mudflats. Species groups such as sculpins (Cottidae) and small flatfish (Pleuronectidae) clearly used specific aquaculture‐growing gear and mudflats in roughly equal proportion. Conclusion: Our results indicate that shellfish farms within a larger nearshore habitat mosaic of eelgrass meadows, mudflats, bivalve aquaculture gear, and edge habitat can provide foraging habitat for several species of nearshore fish. Impact statementShellfish farms within a larger nearshore habitat mosaic of eelgrass meadows, mudflats, bivalve aquaculture gear, and edge habitat can provide foraging habitat for several species of nearshore fish. [ABSTRACT FROM AUTHOR]

Oysters that filter feed can accumulate numerous pathogens, including viruses, which can serve as a valuable viral repository. As oyster farming becomes more prevalent, concerns are mounting about diseases that can harm both cultivated and wild oysters. Unfortunately, there is a lack of research on the viruses and other factors that can cause illness in shellfish. This means that it is harder to find ways to prevent these diseases and protect the oysters. This is part of a previously started project, the Dataset of Oyster Virome, in which we further study 30 almost complete genomes of oyster-associated CRESS DNA viruses. The replication-associated proteins and capsid proteins found in CRESS DNA viruses display varying evolutionary rates and frequently undergo recombination. Additionally, some CRESS DNA viruses have the capability for cross-species transmission. A plethora of unclassified CRESS DNA viruses are detectable in transcriptome libraries, exhibiting higher levels of transcriptional activity than those found in metagenome libraries. The study significantly enhances our understanding of the diversity of oyster-associated CRESS DNA viruses, emphasizing the widespread presence of CRESS DNA viruses in the natural environment and the substantial portion of CRESS DNA viruses that remain unidentified. This study's findings provide a basis for further research on the biological and ecological roles of viruses in oysters and their environment. [ABSTRACT FROM AUTHOR]

Bivalves such as oysters and clams have been farmed in intertidal zones across the Puget Sound region of the Salish Sea for thousands of years. The variety of gear types used on bivalve farms creates complex vertical structure and attachment points for aquatic epiphytes and invertebrates which increases habitat structural complexity, but may alter eelgrass cover in areas where bivalve farms and eelgrass meadows overlap. Eelgrass meadows are highly productive and ecologically foundational near shore habitats that provide valuable ecosystem services including the provision of nursery, refuge, and foraging habitat. Aquaculture has been a key feature of the environment in the Puget Sound for millennia, however, little is known about how well aquaculture practices are integrated into the system, and what services they provide to mobile species assemblages relative to unfarmed eelgrass meadows. We used stable isotope mixing models to estimate, for several species of near shore fish and crab in two areas of North Puget Sound, Washington, the percent diet originating from either a natural bottom habitat (eelgrass meadows), farm habitat (oyster farms), or pelagic planktonic sources. Our results indicate that several species of near shore fish such as surf perch and staghorn sculpin derive a significant proportion of their diets from farm areas, while crabs derive most of their diets from eelgrass habitat, and stickleback derive a significant proportion of their diets from planktonic sources. The results indicate that foraging habitat uses are species specific, and that several species that spatially overlap bivalve farms obtained a large percentage of their diets from adjacent bivalve farm habitat. [ABSTRACT FROM AUTHOR]

This study focuses on market risks oyster farmers face when a Vibrio outbreak occurs from a neighboring farm and investigates the effectiveness of a potential marketing strategy. We conducted an auction field experiment where participants bid on entrées of raw oysters and raw clams over six rounds with two information interventions a press article reporting Vibrio outbreak (negative) and a description of local oyster farmers' effort in outbreak prevention (positive). We found that negative information given first significantly reduced willingness to pay (WTP) for oysters, but subsequent positive information restored WTP. Negative information given as second treatment showed no impact, suggesting positive information's shielding effect. For clams we found evidence of negative information spillover and red-flag effect of positive information. These suggest that oyster farmers could mitigate oyster's demand shocks by disseminating their safe handling practices to consumers, however some caution is warranted for its impact on other shellfish demand. [ABSTRACT FROM AUTHOR]

Glycogen serves as the principal energy reserve for metabolic processes in aquatic shellfish and substantially contributes to the flavor and quality of oysters. The Jinjiang oyster (Crassostrea ariakensis) is an economically and ecologically important species in China. In the present study, RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin using sequencing (ATAC-seq) were performed to investigate gene expression and chromatin accessibility variations in oysters with different glycogen contents. Analysis identified 9 483 differentially expressed genes (DEGs) and 7 215 genes with significantly differential chromatin accessibility (DCAGs) were obtained, with an overlap of 2 600 genes between them. Notably, a significant proportion of these genes were enriched in pathways related to glycogen metabolism, including “Glycogen metabolic process” and “Starch and sucrose metabolism”. In addition, genomewide association study (GWAS) identified 526 single nucleotide polymorphism (SNP) loci associated with glycogen content. These loci corresponded to 241 genes, 63 of which were categorized as both DEGs and DCAGs. This study enriches basic research data and provides insights into the molecular mechanisms underlying the regulation of glycogen metabolism in C. ariakensis. [ABSTRACT FROM AUTHOR]

In the face of an increasing world population and a subsequent need for an increase in sustainable and healthy food production, low trophic species, such as oysters, emerge as a promising alternative. However, regional variations in oyster production techniques, market dynamics, and consumption patterns create challenges for both the global and local industry's growth. In this study, a descriptive qualitative analysis of oyster markets across seven Atlantic regions was carried out. The Pacific oyster (Crassostrea gigas) was found to be farmed in most Atlantic regions except the US but is classified as invasive in Sweden and potentially invasive in South Africa. Other farmed and/or harvested species include native species (C. gasar and C. rhizophorae) in Brazil, the American cupped oyster (C. virginica) in the US, and the European flat oyster (Ostrea edulis) in France, Sweden, and the US. In Irish farms, Pacific oysters are primarily for export to European markets. The marine aquaculture sectors of Sweden, South Africa, and Namibia, as well as Brazil's farming for C. gasar, were found to be underdeveloped. This study also observed a variation in licensing, property rights, and regulatory frameworks. Financial challenges for small businesses, ecological implications of seed production techniques, biosecurity risks, and public health considerations are emphasized as critical areas for attention. This study offers valuable insights into the selected markets and can serve as a useful resource for policymakers, aquaculture practitioners, and stakeholders in optimizing global shellfish industry strategies. [ABSTRACT FROM AUTHOR]

Bivalves such as oysters and clams have been farmed in intertidal zones across the Puget Sound region of the Salish Sea for thousands of years. The variety of gear types used on bivalve farms creates complex vertical structure and attachment points for aquatic epiphytes and invertebrates which increases habitat structural complexity, but may alter eelgrass cover in areas where bivalve farms and eelgrass meadows overlap. Eelgrass meadows are highly productive and ecologically foundational nearshore habitats that provide valuable ecosystem services including the provision of nursery, refuge, and foraging habitat. Aquaculture has been a key feature of the environment in the Puget Sound for millennia, however, little is known about how well aquaculture practices are integrated into the system, and what services they provide to mobile species assemblages relative to unfarmed eelgrass meadows. We used stable isotope mixing models to estimate, for several species of nearshore fish and crab in two areas of North Puget Sound, Washington, the percent diet originating from either a natural bottom habitat (eelgrass meadows), farm habitat (oyster farms), or pelagic planktonic sources. Our results indicate that several species of nearshore fish such as surf perch and staghorn sculpin derive a significant proportion of their diets from farm areas, while crabs derive most of their diets from eelgrass habitat, and stickleback derive a significant proportion of their diets from planktonic sources. The results indicate that foraging habitat uses are species specific, and that several species that spatially overlap bivalve farms obtained a large percentage of their diets from adjacent bivalve farm habitat.

Vibrio spp. are ubiquitous bacteria that are frequently discovered in aquatic environments. Globally, they are recognized as the primary cause of seafood-related illnesses. Over decades, vibrios have been a major health concern, and the number of cases is on the rise due to unhygienic eating habits and increasing demand for raw seafood. Among the 2 groups of Vibrio bacteria, the non-cholera Vibrio bacteria group mainly associate with seafood-borne illness. Though ~ 12 species have been recognized as causative agents of diseases in humans, horizontal gene transfer has attributed to an increase in emerging human pathogenic Vibrio spp. The assortment of virulence determinants contributes to the pathogenicity of vibrios. They carry specific genes to produce toxins and hemolysin, which are correlated with pathogenicity. In addition, the expanding antimicrobial use in humans and aquaculture resulted in a surge of resistant Vibrio strains found in shellfish. This has adversely affected the therapeutic results in the case of Vibrio infection. Thus, this article provides insight into the potential public health threat that may pose to seafood consumers as a consequence of the presence of virulence factors and antimicrobial resistance determinants in molluscan shellfish-borne vibrios. [ABSTRACT FROM AUTHOR]

Oysters play an important role in coastal ecology and are a globally popular seafood source. However, their filter-feeding lifestyle enables coastal pathogens, toxins, and pollutants to accumulate in their tissues, potentially endangering human health. While pathogen concentrations in coastal waters are often linked to environmental conditions and runoff events, these do not always correlate with pathogen concentrations in oysters. Additional factors related to the microbial ecology of pathogenic bacteria and their relationship with oyster hosts likely play a role in accumulation but are poorly understood. In this study, we investigated whether microbial communities in water and oysters were linked to accumulation of Vibrio parahaemolyticus, Vibrio vulnificus, or fecal indicator bacteria. Site-specific environmental conditions significantly influenced microbial communities and potential pathogen concentrations in water. Oyster microbial communities, however, exhibited less variability in microbial community diversity and accumulation of target bacteria overall and were less impacted by environmental differences between sites. Instead, changes in specific microbial taxa in oyster and water samples, particularly in oyster digestive glands, were linked to elevated levels of potential pathogens. For example, increased levels of V. parahaemolyticus were associated with higher relative abundances of cyanobacteria, which could represent an environmental vector for Vibrio spp. transport, and with decreased relative abundance of Mycoplasma and other key members of the oyster digestive gland microbiota. These findings suggest that host and microbial factors, in addition to environmental variables, may influence pathogen accumulation in oysters. [ABSTRACT FROM AUTHOR]

It has long been suggested by commercial fishing interests that the sea bed benefits from being trawled or disturbed. Evidence to support increased benthic food web productivity in areas disturbed by trawling has suggested that this is the case, and that some mobile consumers can benefit from this increased productivity.The same hypothesis has been put forward for shellfish recruitment, that disturbance of the sea bed, e.g. 'harrowing', increases the exposure of suitable settlement substrates for shellfish larvae. This is an approach often taken in shellfish mariculture in private fisheries, and has led to calls for support of expanding such activities into publicly managed areas to promote shellfish recovery and restoration.Increased seabed disturbance, however, may not align with conservation policy or societal objectives for natural recovery of the seabed landscape. Furthermore, evidence for increased shellfish recruitment from seabed disturbance is mixed, and many attempts to elucidate whether relationships exist receive criticism for operating at small spatial and temporal scales.An analysis is presented from 3 years of data (2016–2018) from a stock survey of a private European flat oyster, Ostrea edulis, fishery operating in the Blackwater estuary, Essex, UK. Using data for adult and recruit oyster abundance and distribution in 2018, with 'harrowing' effort from 2016–2018, it is asked whether oyster recruitment was related to disturbance effort.It was found that oyster recruitment is positively related to increased seabed disturbance, but only up to intermediate adult oyster abundance equivalent to 60 oysters/100 m dredge, beyond which harrowing results in recruitment declines. This has implications for approaches to oyster fishery recovery, but also for restoration projects seeking evidence‐led guidance on which ways may be appropriate to kick‐start natural recovery in historical oyster areas that are habitat limited. [ABSTRACT FROM AUTHOR]

The disposal of treated and untreated sewage near shellfish harvesting areas is a global concern. Discharged sewage may be contaminated with enteric viruses present in human faeces. Bivalve molluscs, in turn, act as vectors for enteric viruses through bioaccumulation and retention of these viruses during the filter-feeding process, resulting in outbreaks of infections due to the consumption of contaminated shellfish. This review was conducted using peer-reviewed articles published from 2012 until September 2022, obtained from online databases such as Google Scholar, Scopus, and Science Direct, highlighting the challenges that the shellfish industry is faced with concerning pollutants ending up in the shellfish production areas. Developed countries have made some advancements by upgrading sewage infrastructures, which reduced viral loads in sewage. However, it is difficult to measure the significance of these improvements, as there are no regulations in place which stipulate the permissible limits for viruses. In most developing countries, including South Africa, there is a lack of effective management plans for virus monitoring in shellfish harvesting areas. The findings of this study indicated a need for extensive research on the origin of viruses, their interactions with other organisms within the marine ecosystem, the quantification of viruses within the Saldanha Bay harbour, and the development of virus management plans which currently are non-existent. [ABSTRACT FROM AUTHOR]

Oyster is one of the four favorite cultured shellfish in China, particularly in the high content of mineral elements rich in vitamins and high-quality proteins. However, the meat of oysters was easy to be infected by external microorganisms, due to the direct exposure to the air after opening. In addition, the fat oxidation, yellowing, and juice loss of oyster meat can also occur during storage, leading to destroy the sensory quality and the economic value of oysters. Therefore, it is necessary for new and efficient sterilization to inhibit microbial contamination for oyster preservation. Traditional thermal sterilization technology mainly transmits a large amount of heat energy to the food via heat conduction, in order to achieve the purpose of killing microorganisms and inactivating enzymes at high temperatures. However, some damage can often occur to the food texture and flavor during thermal sterilization. Fortunately, the Sono-photodynamic sterilization technology (SPDT) is a new type of sterilization to combine sonodynamic and photodynamic technology. The sterilization can be expected to activate the Sono-photosensitizer molecules for a series of active oxygen bactericidal substances under the action of a specific wavelength of light and ultrasound. The purpose of this study is to explore the preservation effect of sono-photodynamic sterilization technology on oysters in view of the shortcomings of photodynamic sterilization and sonodynamic sterilization technology alone. Firstly, the growth curve was drawn for the total colonies number of microorganisms in oysters at 4℃. The initial colony number of oysters was (4.02±0.02) lg (CFU/g), and the shelf life was only 6 days. Then, orthogonal experiments were carried out based on the single factor experiments of curcumin concentration, sono-photodynamic processing time and ultrasonic power. The results showed that the fresh oysters treated with 50 umol/L curcumin, 600 W ultrasonic power for 60 min LED exposure presented the best preservation effects, and the total number of bacterial colonies was 4.52 lg (CFU/g). Finally, the quality changes of oyster products were evaluated to determine the total bacterial count and volatile base nitrogen under the optimal preservation parameters of Sono-photodynamic sterilization. The results showed that the Sono-photodynamic sterilization was used to effectively kill the microorganisms in the oysters for the extending shelf life of oysters to 12 days. The thiobarbituric acid value determination showed that the light in the Sono-photodynamic sterilization accelerated the oxidation of oyster fat. Therefore, the sterilization effect and exposure time were considered under oxidation reaction conditions. The color difference analysis, pH value, and hardness measurement showed that the Sono-photodynamic sterilization can be expected to effectively delay the color change of oysters, and then control the spoilage rate of oysters, finally preventing the autolysis of oysters. The sensory evaluation showed that the Sono-photodynamic sterilization can maintain the product quality for the longer shelf life of oysters. In general, comparison of sono-photodynamic group with control group, curcumin group, illumination group and ultrasonic group, sono-photodynamic group can keep the pH value, thiobarbituric acid and volatile base nitrogen of oysters at low values, maintain the sensory quality of oysters such as appearance, hardness and color, and prolong the shelf life of oysters from 6 days to 12 days at 4 ℃. In summary, Sono-photodynamic sterilization can be used to obtain better bactericidal activity for the preservation of oysters. [ABSTRACT FROM AUTHOR]

Background: Given the recent detection of tetrodotoxin (TTX) in bivalve molluscs but the absence of a full collaborative validation study for TTX determination in a large number of shellfish samples, interlaboratory assessment of method performance was required to better understand current capabilities for accurate and reproducible TTX quantitation using chemical and immunoassay methods. Objective: The aim was to conduct an interlaboratory study with multiple laboratories, using results to assess method performance and acceptability of different TTX testing methods. Methods: Homogenous and stable mussel and oyster materials were assessed by participants using a range of published and in-house detection methods to determine mean TTX concentrations. Data were used to calculate recoveries, repeatability, and reproducibility, together with participant acceptability z-scores. Results: Method performance characteristics were good, showing excellent sensitivity, recovery, and repeatability. Acceptable reproducibility was evidenced by HorRat values for all LC-MS/MS and ELISA methods being less than the 2.0 limit of acceptability. Method differences between the LC-MS/MS participants did not result in statistically different results. Method performance characteristics compared well with previously published single-laboratory validated methods and no statistical difference was found in results returned by ELISA in comparison with LC-MS/MS. Conclusion: The results from this study demonstrate that current LC-MS/MS methods and ELISA are on the whole capable of sensitive, accurate, and reproducible TTX quantitation in shellfish. Further work is recommended to expand the number of laboratories testing ELISA and to standardize an LC-MS/MS protocol to further improve interlaboratory precision. Highlights: Multiple mass spectrometric methods and a commercial ELISA have been successfully assessed through an interlaboratory study, demonstrating excellent performance. [ABSTRACT FROM AUTHOR]

Importation and translocation of seeds and live animals for aquaculture purposes are well-established practices in the European and Italian shellfish market. However, these routines may be responsible for alien species introduction and spread, representing a risk for aquaculture activities, human health, as well as for environmental and biodiversity conservation. To estimate and reduce the potential impact of alien and locally absent species on aquatic habitats due to aquaculture practices, Member States have adopted Council Regulation (EC) No 708/2007, which provides guidance for risk analysis and contingency measures for mitigation. Despite this legal framework, traceability data for shellfish movements are currently lacking and need to be improved in all EU Member States. The present work presents an updated literature summary of alien species associated with bivalve farming and trading. The information herein collected will be helpful to upgrade the traceability system of farmed bivalves in Italian marine waters with reference to non-target species, representing a knowledge baseline for setting bio security plans to reduce their risk of introduction and further spreading. [ABSTRACT FROM AUTHOR]

Pacific oyster (Crassostrea gigas), an abundant bivalve consumed across the Pacific, is known to possess a wide range of bioactivities. While there has been some work on its bioactive hydrolysates, the discovery of bioactive peptides (BAPs) remains limited due to the resource-intensive nature of the existing discovery pipeline. To overcome this constraint, in silico-based prospecting is employed to accelerate BAP discovery. Major oyster proteins were digested virtually under a simulated gastrointestinal condition to generate virtual peptide products that were screened against existing databases for peptide bioactivities, toxicity, bitterness, stability in the intestine and in the blood, and novelty. Five peptide candidates were shortlisted showing antidiabetic, anti-inflammatory, antihypertensive, antimicrobial, and anticancer potential. By employing this approach, oyster BAPs were identified at a faster rate, with a wider applicability reach. With the growing market for peptide-based nutraceuticals, this provides an efficient workflow for candidate scouting and end-use investigation for targeted functional product preparation. [ABSTRACT FROM AUTHOR]

This volume of Evolutionary Applications sees the publication of two genomes for the European native flat oyster Ostrea edulis, a species of significant evolutionary, ecological and commercial value. Each is a highly contiguous chromosome‐level assembly from individuals of different genetic backgrounds, which have been benchmarked against one another. This situation has resulted from the serendipitous discovery that two independent research groups were both deep into the process of building, annotating and investigating separately produced assemblies. Due to constraints with funder requirements and the need to recognize early career researchers for their work, alongside the technical challenge of integrating assemblies from two very different genomes, there was limited capacity to merge the sequences into one publication at the stage of discovery. This issue is likely to become very common over the next few years until the technologies for working with multiple genomes at once, for example, graph genomes, become commonplace in nonmodel species. Consequently, both of our teams have decided to collaborate rather than compete, recognizing the benefit to copublishing two separate genome resources for the research community, each with distinct scientific investigations, and working collaboratively to benchmark the assemblies. [ABSTRACT FROM AUTHOR]