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Journal articles on the topic 'Oyster contamination'
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1
COLE, MARY TOWNSEND, MARILYN B. KILGEN, and CAMERON R. HACKNEY. "Evaluation of Methods for Extraction of Enteric Virus from Louisiana Oysters." Journal of Food Protection 49, no. 8 (August 1, 1986): 592–95. http://dx.doi.org/10.4315/0362-028x-49.8.592.
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Six techniques were evaluated for recovery of poliovirus from Louisiana oysters. The methods were compared for percent recovery rates, toxicity, ease of extraction, bacterial contamination, and final volume of oyster concentrate. Oyster samples were contaminated with 30–40 plaque forming units of Poliovirus type 1 and processed by six variations of adsorption-elution-precipitation and elution-precipitation methods. The method developed by Ellender et al. (Natural enterovirus and fecal coliform contamination of gulf coast oysters. J. Food Prot. 43:105–110) was judged to be the preferred method for gulf coast oysters.
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COOK, DAVID W., and R. D. ELLENDER. "Relaying to Decrease the Concentration of Oyster-Associated Pathogens." Journal of Food Protection 49, no. 3 (March 1, 1986): 196–202. http://dx.doi.org/10.4315/0362-028x-49.3.196.
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Oysters experimentally contaminated with indicator bacteria, Salmonella and poliovirus were used in relaying studies designed to measure microbial elimination under a variety of environmental conditions. Two factors, level of microorganism in the oyster and temperature of the water, were important in determining the length of time necessary to purge the contaminating organisms. Oysters under physiological stress cleansed at a slower rate than did healthy oysters. Based on the expected level of pathogen contamination in naturally polluted oysters, healthy relaid oysters were capable of cleansing in a 7-d period provided the temperature was above 10°C. These results were verified by following the elimination of indicator bacteria and poliovirus in commercially relaid oysters. Fecal indicator bacteria and enteric pathogenic bacteria were eliminated at similar rates but fecal coliform levels did not correlate with virus elimination. Relaying waters may contain some indicator bacteria and this study suggested that fecal coliforms may not be useful as end-point indicators for this method of oyster purification.
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Boher, S., and L. Schwartzbrod. "Study of Viral Purification of Oysters." Water Science and Technology 27, no. 3-4 (February 1, 1993): 55–60. http://dx.doi.org/10.2166/wst.1993.0321.
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Oysters (Crassostrea gigas) were experimentally contaminated by immersion in seawater containing rotaviruses SAl 1 for one hour. The rotaviruses SAl 1 had previously been adsorbed over algae (Dunaliella primolecta). Oyster depuration was then studied. The depuration was performed by immersion in closed loop circuit and in semi open circuit. In the semi open circuit, the seawater is replaced every 24 hours. It was shown that the rotaviruses, whether free or fixed on algae, were inactivated very rapidly when the seawaterwascontinuously treated with U.V. (intensity ranging from 46.5 to 94 mW.s/cm2). The decontamination of the oysters in closed loop circuit starts at the first hours of immersion. For large viral contaminations, the decontamination was complete in 78 % of the cases after 72 hours. In the remaining 23 % of the cases, the contamination decrease varied from 82 % to 99.7 %. For lower viral contaminations, less than 30 viruses per gram of oyster tissue, the depuration was complete in 100 % of the cases after 72 hours. For large viral contaminations, the decontamination in semi open circuit was complete in only 82 % of the cases after 72 hours. For contaminations lower than 30 viruses per gram of oyster tissue, the dqjuration was complete in 100 % of the cases after 72 hours.
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Jeamsripong, Saharuetai, Rungtip Chuanchuen, and Edward Atwill. "Assessment of Bacterial Accumulation and Environmental Factors in Sentinel Oysters and Estuarine Water Quality from the Phang Nga Estuary Area in Thailand." International Journal of Environmental Research and Public Health 15, no. 9 (September 10, 2018): 1970. http://dx.doi.org/10.3390/ijerph15091970.
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This study characterized microbiological and chemical contamination of oyster meat and estuarine water in Phang Nga, Thailand. Pooled oyster meats (n = 144), estuarine waters (n = 96) and environmental parameters were collected from March, 2016 to February, 2017, and assessed for levels of total coliforms (TC), fecal coliforms (FC), Escherichia coli (EC), and Vibrio parahaemolyticus (VP), presence of Salmonella and Shigella and levels of heavy metals (Mn, Pb and Cd). The prevalence of TC, FC and EC were in 99.3%, 94.4% and 93.1% of oyster meat and 94.8%, 79.2%, and 78.1% of water, respectively. The average VP levels was 8.5 × 107 most probable number (MPN)/g oyster. Prevalence of Shigella and Salmonella in the pooled oysters were 7.6% and 30.6%, respectively. The dominant Salmonella serovars were Paratyphi B followed by Seremban, and Kentucky. In contrast, the prevalence of Shigella were 27.1%, but Salmonella was not detected in estuarine water. Factors statistically associated with EC accumulation in oyster were level of FC, 7-day average precipitation, temperature, relative humidity, and presence of Salmonella in the sample. The optimal cutoff value of EC to predict Salmonella in oyster was 420 MPN/g. Results indicate this area has relatively safe levels of heavy metals, whereas bacterial contamination was very high for oysters.
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SU, YI-CHENG, QIANRU YANG, and CLAUDIA HÄSE. "Refrigerated Seawater Depuration for Reducing Vibrio parahaemolyticus Contamination in Pacific Oyster (Crassostrea gigas)." Journal of Food Protection 73, no. 6 (June 1, 2010): 1111–15. http://dx.doi.org/10.4315/0362-028x-73.6.1111.
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The efficacy of refrigerated-seawater depuration for reducing Vibrio parahaemolyticus levels in Pacific oyster (Crassostrea gigas) was investigated. Raw Pacific oysters were inoculated with a mixed culture of five clinical strains of V. parahaemolyticus (105 to 106 most probable number [MPN] per g) and depurated with refrigerated seawater (5°C) in a laboratory-scale recirculation system equipped with a 15-W gamma UV sterilizer. Depuration with refrigerated seawater for 96 h reduced V. parahaemolyticus populations by >3.0 log MPN/g in oysters harvested in the winter. However, 144 h of depuration at 5°C was required to achieve a 3-log reduction in oysters harvested in the summer. Depuration with refrigerated seawater at 5°C for up to 144 h caused no significant fatality in the Pacific oyster and could be applied as a postharvest treatment to reduce V. parahaemolyticus contamination in Pacific oysters. Further studies are needed to validate the efficacy of the depuration process for reducing naturally accumulated V. parahaemolyticus in oysters.
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Jeamsripong, Saharuetai, and Edward R. Atwill. "Modelling of Indicator Escherichia coli Contamination in Sentinel Oysters and Estuarine Water." International Journal of Environmental Research and Public Health 16, no. 11 (June 4, 2019): 1971. http://dx.doi.org/10.3390/ijerph16111971.
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This study was performed to improve the ability to predict the concentrations of Escherichia coli in oyster meat and estuarine waters by using environmental parameters, and microbiological and heavy metal contamination from shellfish growing area in southern Thailand. Oyster meat (n = 144) and estuarine waters (n = 96) were tested for microbiological and heavy metal contamination from March 2016 to February 2017. Prevalence and mean concentrations of E. coli were 93.1% and 4.6 × 103 most probable number (MPN)/g in oyster meat, and 78.1% and 2.2 × 102 MPN/100 mL in estuarine water. Average 7-day precipitation, ambient air temperature, and the presence of Salmonella were associated with the concentrations of E. coli in oyster meat (p < 0.05). Raw data (MPN/g of oyster meat and MPN/100 mL of estuarine water) and log-transformed data (logMPN/g of oyster meat and logMPN/100 mL of estuarine water) of E. coli concentrations were examined within two contrasting regression models. However, the more valid predictions were conducted using non-log transformed values. These findings indicate that non-log transformed data can be used for building more accurate statistical models in microbiological food safety, and that significant environmental parameters can be used as a part of a rapid warning system to predict levels of E. coli before harvesting oysters.
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Brandão, Maria Aparecida da RessurreiÇão, Amanda Teixeira Sampaio Lopes, Maria Tereza da Silva Neta, Rhyan Barros Farias de Oliveira, Rachel Passos Rezende, George Rêgo Albuquerque, Verônica Dias Gonçalves, Dália dos Prazeres Rodrigues, Guisla Boehs, and Bianca Mendes Maciel. "Microbiological Quality and Prevalence of β-Lactam Antibiotic Resistance Genes in Oysters (Crassostrea rhizophorae)." Journal of Food Protection 80, no. 3 (February 16, 2017): 488–96. http://dx.doi.org/10.4315/0362-028x.jfp-16-098.
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ABSTRACTThe microbiological quality of oysters reflects the microbiological quality of their habitats because they are filter feeders. The objective of this study was to assess the bacterial composition of the edible oyster Crassostrea rhizophorae in urban and preserved estuaries. Particularly, we assessed the presence of pathogenic bacteria, investigated antibiotic susceptibility in bacterial isolates, and quantified β-lactam antibiotic resistance genes (blaTEM, blaSHV, and blaKPC) via quantitative PCR of oyster DNA. Our results detected total coliforms, Escherichia coli, and enterobacteria in the oysters from urban estuaries, which is indicative of poor water quality. In addition, our detection of the eaeA and stxA2 virulence genes in 16.7% of E. coli isolates from oysters from this region suggests the presence of multiantibiotic-resistant enteropathogenic and enterohemorrhagic E. coli strains. During periods of low precipitation, increased contamination by E. coli (in winter) and Vibrio parahaemolyticus (in autumn) was observed. In contrast, cultivated oysters inhabiting monitored farms in preserved areas had low levels of bacterial contamination, emphasizing that oyster culture monitoring enhances food quality and makes oysters fit for human consumption. Distinct antibiotic resistance profiles were observed in bacteria isolated from oysters collected from different areas, including resistance to β-lactam antibiotics. The presence of the blaTEM gene in 91.3% of oyster samples indicated that microorganisms in estuarine water conferred the capability to produce β-lactamase. To our knowledge, this is the first study to directly quantify and detect β-lactam antibiotic resistance genes in oysters. We believe our study provides baseline data for bacterial dynamics in estuarine oysters; such knowledge contributes to developing risk assessments to determine the associated hazards and consequences of consuming oysters from aquatic environments containing pathogenic bacteria that may possess antibiotic resistance genes.
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Zakhour, Maha, Haifa Maalouf, Ilaria Di Bartolo, Larissa Haugarreau, Françoise S. Le Guyader, Nathalie Ruvoën-Clouet, Jean-Claude Le Saux, Franco Maria Ruggeri, Monique Pommepuy, and Jacques Le Pendu. "Bovine Norovirus: Carbohydrate Ligand, Environmental Contamination, and Potential Cross-Species Transmission via Oysters." Applied and Environmental Microbiology 76, no. 19 (August 13, 2010): 6404–11. http://dx.doi.org/10.1128/aem.00671-10.
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ABSTRACT Noroviruses (NoV) are major agents of acute gastroenteritis in humans and the primary pathogens of shellfish-related outbreaks. Previous studies showed that some human strains bind to oyster tissues through carbohydrate ligands that are similar to their human receptors. Thus, based on presentation of shared norovirus carbohydrate ligands, oysters could selectively concentrate animal strains with increased ability to overcome species barriers. In comparison with human GI and GII strains, bovine GIII NoV strains, although frequently detected in bovine feces and waters of two estuaries of Brittany, were seldom detected in oysters grown in these estuaries. Characterization of the carbohydrate ligand from a new GIII strain indicated recognition of the alpha-galactosidase (α-Gal) epitope not expressed by humans, similar to the GIII.2 Newbury2 strain. This ligand was not detectable on oyster tissues, suggesting that oysters may not be able to accumulate substantial amounts of GIII strains due to the lack of shared carbohydrate ligand and that they should be unable to contribute to select GIII strains with an increased ability to recognize humans.
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BRILLHART, CRYSTAL D., and LYNN A. JOENS. "Prevalence and Characterization of Salmonella Serovars Isolated from Oysters Served Raw in Restaurants." Journal of Food Protection 74, no. 6 (June 1, 2011): 1025–29. http://dx.doi.org/10.4315/0362-028x.jfp-10-443.
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To determine if Salmonella-contaminated oysters are reaching consumer tables, a survey of raw oysters served in eight Tucson restaurants was performed from October 2007 to September 2008. Salmonella spp. were isolated during 7 of the 8 months surveyed and were present in 1.2% of 2,281 oysters tested. This observed prevalence is lower than that seen in a previous study in which U.S. market oysters were purchased from producers at bays where oysters are harvested. To test whether the process of refrigerating oysters in restaurants for several days reduces Salmonella levels, oysters were artificially infected with Salmonella and kept at 4°C for up to 13 days. Direct plate counts of oyster homogenate showed that Salmonella levels within oysters did not decrease during refrigeration. Six different serovars of Salmonella enterica were found in the restaurant oysters, indicating multiple incidences of Salmonella contamination of U.S. oyster stocks. Of the 28 contaminated oysters, 12 (43%) contained a strain of S. enterica serovar Newport that matched by pulsed-field gel electrophoresis a serovar Newport strain seen predominantly in the study of bay oysters performed in 2002. The repeated occurrence of this strain in oyster surveys is concerning, since the strain was resistant to seven antimicrobials tested and thus presents a possible health risk to consumers of raw oysters.
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Florini, Styliano, Esmaeil Shahsavari, Arturo Aburto-Medina, Leadin S. Khudur, Stephen M. Mudge, David J. Smith, and Andrew S. Ball. "Are Sterols Useful for the Identification of Sources of Faecal Contamination in Shellfish? A Case Study." Water 12, no. 11 (November 2, 2020): 3076. http://dx.doi.org/10.3390/w12113076.
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This work aimed to identify the major source(s) of faecal pollution impacting Salcott Creek oyster fisheries in the UK through the examination of the sterol profiles. The concentration of the major sewage biomarker, coprostanol, in water overlying the oysters varied between 0.01 µg L−1 and 1.20 µg L−1. The coprostanol/epicoprostanol ratio ranged from 1.32 (September) to 33.25 (February), suggesting that human sewage represents the key input of faecal material into the estuary. However, a correlation between the sterol profile of water above the oysters with that of water that enters from Tiptree Sewage Treatment Works (r = 0.82), and a sample from a site (Quinces Corner) observed to have a high population of Brent geese (r = 0.82), suggests that both sources contribute to the faecal pollution affecting the oysters. In identifying these key faecal inputs, sterol profiling has allowed targeted management practices to be employed to ensure that oyster quality is optimised.
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TAMBER, SANDEEP, ALEX MONTGOMERY, KATIE ELORANTA, and ENRICO BUENAVENTURA. "Enumeration and Survival of Salmonella enterica in Live Oyster Shellstock Harvested from Canadian Waters." Journal of Food Protection 83, no. 1 (December 4, 2019): 6–12. http://dx.doi.org/10.4315/0362-028x.jfp-19-318.
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ABSTRACT Since 2015, 11 recalls of live oyster shellstock have been issued in Canada due to the presence of Salmonella enterica. Six of those recalls took place in 2018. To understand this increase, fundamental information is needed on the relationship between S. enterica and oysters. The aims of this study were to address important data gaps concerning the levels of Salmonella in naturally contaminated oysters and the ability of this pathogen to survive in live oyster shellstock. Enumeration data were evaluated for five oyster and clam samples collected from the east coast of Canada from 2015 to 2018. The reported levels were <0.0015 to 0.064 most probable number per g of oyster tissue. The S. enterica isolates recovered from these animals belonged to serovars Typhimurium, Infantis, Enteritidis, and I 4,5:i:−. Filter feeding by the oysters was exploited to assess the Salmonella accumulation that would occur following a natural contamination event. Detectable levels of the pathogen were observed after 30 min of exposure and began to plateau at 60 min. A survival study in live oyster shellstock indicated that after 4 days of storage at ambient temperatures, the Salmonella level declined slightly from 4.3 to 3.7 log CFU/g. These data indicate that the levels of Salmonella found in naturally contaminated oysters are low and are not expected to increase between the point of harvest and the point of consumption. The changing ecology of shellfish environments requires continued monitoring and testing to safeguard public health. The data presented here will be useful for the evaluation and design of sampling plans and risk management approaches for the control of Salmonella in live oyster shellstock. HIGHLIGHTS
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LYDON, KERI ANN, MELISSA FARRELL-EVANS, and JESSICA L. JONES. "Evaluation of Ice Slurries as a Control for Postharvest Growth of Vibrio spp. in Oysters and Potential for Filth Contamination." Journal of Food Protection 78, no. 7 (July 1, 2015): 1375–79. http://dx.doi.org/10.4315/0362-028x.jfp-14-557.
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Raw oyster consumption is the most common route of exposure for Vibrio spp. infections in humans. Vibriosis has been increasing steadily in the United States despite efforts to reduce the incidence of the disease. Research has demonstrated that ice is effective in reducing postharvest Vibrio spp. growth in oysters but has raised concerns of possible contamination of oyster meat by filth (as indicated by the presence of fecal coliform bacteria or Clostridium perfringens). This study examined the use of ice slurries (<4.5°C) to reduce Vibrio growth. Ice slurries showed rapid internal cooling of oysters, from 23.9°C (75°F) to 10°C (50°F) within 12 min. The initial bacterial loads in the ice slurry waters were near the limits of detection. Following repeated dipping of oysters into ice slurries, water samples exhibited significant (P < 0.05) increases in median levels of fecal coliforms (9.5 most probable number [MPN]/100 ml), C. perfringens (280 MPN/100 ml), Vibrio vulnificus (11,250 MPN/ml), and total Vibrio parahaemolyticus (3,900 MPN/ml). The microbial load in oyster meat, however, was unchanged after 15 min of submergence, with no significant differences (P < 0.05) in levels of filth indicator (range, 250 to 720 MPN/100 g) or Vibrio spp. (range, 9,000 to 20,000 MPN/g) bacteria. These results support the use of ice slurries as a postharvest application for rapid cooling of oysters to minimize Vibrio growth.
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Ueki, Y., K. Akiyama, T. Watanabe, and T. Omura. "Genetic analysis of noroviruses taken from gastroenteritis patients, river water and oysters." Water Science and Technology 50, no. 1 (July 1, 2004): 51–56. http://dx.doi.org/10.2166/wst.2004.0016.
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As oysters are eaten raw in Japan, their contamination with the non-bacterial agent of gastroenteritis has become a serious health problem. As it is well known that oysters tend to concentrate noroviruses (NV) in their digestive diverticula, NV may be linked with the acute gastroenteritis. However, since NV cannot be cultivated in cell cultures, and they have genetic diversity, the behaviour of NV in the aquatic environment is little known. In this study, NV samples were taken from gastroenteritis patients; from the river flowing into the oyster-farming area; and from oysters harvested from that river. Genetic identities of NV samples were analysed in capsid and RNA-dependent RNA polymerase (RdRp) regions respectively. In both regions, strains taken from patients were >96% identical with those from river and oyster samples. This proved that oysters were contaminated with NV excreted from patients with gastroenteritis.
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Lowther, James A., Nicole E. Gustar, Andrew L. Powell, Rachel E. Hartnell, and David N. Lees. "Two-Year Systematic Study To Assess Norovirus Contamination in Oysters from Commercial Harvesting Areas in the United Kingdom." Applied and Environmental Microbiology 78, no. 16 (June 8, 2012): 5812–17. http://dx.doi.org/10.1128/aem.01046-12.
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ABSTRACTThe contamination of bivalve shellfish with norovirus from human fecal sources is recognized as an important human health risk. Standardized quantitative methods for the detection of norovirus in molluscan shellfish are now available, and viral standards are being considered in the European Union and internationally. This 2-year systematic study aimed to investigate the impact of the application of these methods to the monitoring of norovirus contamination in oyster production areas in the United Kingdom. Twenty-four monthly samples of oysters from 39 United Kingdom production areas, chosen to represent a range of potential contamination risk, were tested for norovirus genogroups I and II by using a quantitative real-time reverse transcription (RT)-PCR method. Norovirus was detected in 76.2% (643/844) of samples, with all sites returning at least one positive result. Both prevalences (presence or absence) and norovirus levels varied markedly between sites. However, overall, a marked winter seasonality of contamination by both prevalence and quantity was observed. Correlations were found between norovirus contamination and potential risk indicators, including harvesting area classifications,Escherichia coliscores, and environmental temperatures. A predictive risk score for norovirus contamination was developed by using a combination of these factors. In summary, this study, the largest of its type undertaken to date, provides a systematic analysis of norovirus contamination in commercial oyster production areas in the United Kingdom. The data should assist risk managers to develop control strategies to reduce the risk of human illness resulting from norovirus contamination of bivalve molluscs.
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Shieh, Y. S. Carol, Kevin R. Calci, and Ralph S. Baric. "A Method To Detect Low Levels of Enteric Viruses in Contaminated Oysters." Applied and Environmental Microbiology 65, no. 11 (November 1, 1999): 4709–14. http://dx.doi.org/10.1128/aem.65.11.4709-4714.1999.
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ABSTRACT Direct isolation and identification of pathogenic viruses from oysters implicated in gastroenteritis outbreaks are hampered by inefficient methods for recovering viruses, naturally occurring PCR inhibitors, and low levels of virus contamination. In this study we focused on developing rapid and efficient oyster-processing procedures that can be used for sensitive PCR detection of viruses in raw oysters. Poliovirus type 3 (PV3) Sabin strain was used to evaluate the efficacy of virus recovery and the removal of PCR inhibitors during oyster-processing procedures. These procedures included elution, polyethylene glycol precipitation, solvent extraction, and RNA extraction. Acid adsorption-elution in which glycine buffer (pH 7.5) was used was found to retain fewer inhibitors than direct elution in which glycine buffer (pH 9.5) was used. RNA extraction in which a silica gel membrane was used was more effective than single-step RNA precipitation for removing additional nonspecific PCR inhibitors. The final 10-μl volume of RNA concentrates obtained from 2 g of oyster tissue (concentration factor, 200-fold) was satisfactory for efficient reverse transcription-PCR detection of virus. The overall detection sensitivity of our method was 1 PFU/g of oyster tissue initially seeded with PV3. The method was utilized to investigate a 1998 gastroenteritis outbreak in California in which contaminated oysters were the suspected disease transmission vehicle. A genogroup II Norwalk-like virus was found in two of three recalled oyster samples linked by tags to the harvest dates and areas associated with the majority of cases. The method described here improves the response to outbreaks and can be used for rapid and sensitive detection of viral agents in outbreak-implicated oysters.
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Florini, Styliani, Esmaeil Shahsavari, Tien Ngo, Arturo Aburto-Medina, David J. Smith, and Andrew S. Ball. "Factors Influencing the Concentration of Fecal Coliforms in Oysters in the River Blackwater Estuary, UK." Water 12, no. 4 (April 11, 2020): 1086. http://dx.doi.org/10.3390/w12041086.
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Contamination of water systems can not only entail high risks to human health but can also result in economic losses due to closure of beaches and shellfish harvesting areas. Understanding the origin of fecal pollution at locations where shellfish are grown is essential in assessing associated health risks—as well as the determining actions necessary to remedy the problem. The aim of this work is to identify the species-specific source(s) of fecal contamination impacting waters overlying the shellfisheries in the Blackwater Estuary, East Anglia, UK. Over a twelve-month period, water samples were taken from above the oysters and from a variety of upstream points considered to be likely sources of fecal microorganism, together with oyster samples, and the number of fecal streptococci and E. coli were determined. Transition from low to high tide significantly decreased the concentration of fecal streptococci in waters overlying the oyster beds, indicative of a freshwater input of fecal pollution in oyster bed waters. In 12 months, the number of E. coli remained constant throughout, while fecal streptococci numbers were generally higher in the winter months. Analyses of upstream samples identified a sewage outfall to be the main source of E. coli to the oyster beds, with additional fecal streptococci from agricultural sources. The findings may assist in developing approaches for assessing the risks to shellfishery industries of various fecal inputs into an estuary, which could then help local governmental authorities address the problem.
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VENTRONE, IOLE, JULIEN SCHAEFFER, JOANNA OLLIVIER, SYLVAIN PARNAUDEAU, TIZIANA PEPE, JACQUES LE PENDU, and FRANÇOISE S. LE GUYADER. "Chronic or Accidental Exposure of Oysters to Norovirus: Is There Any Difference in Contamination?" Journal of Food Protection 76, no. 3 (March 1, 2013): 505–9. http://dx.doi.org/10.4315/0362-028x.jfp-12-296.
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Bivalve molluscan shellfish such as oysters may be contaminated by human pathogens. Currently, the primary pathogens associated with shellfish-related outbreaks are noroviruses. This study was conducted to improve understanding of oyster bioaccumulation when oysters were exposed to daily contamination or one accidental contamination event, i.e., different modes of contamination. Oysters were contaminated with two representative strains of norovirus (GI.1 and GII.3) and then analyzed with real-time reverse transcription PCR. Exposure to a repeated virus dose for 9 days (mimicking a growing area subjected to frequent sewage contamination) led to an additive accumulation that was not significantly different from that obtained when the same total dose of virus was added all at once (as may happen after accidental sewage discharge). Similarly, bioaccumulation tests performed with mixed strains revealed additive accumulation of both viruses. Depuration may not be efficient for eliminating viruses; therefore, to prevent contaminated shellfish from being put onto the market, continuous sanitary monitoring must be considered. All climatic events or sewage failures occurring in production areas must be recorded, because repeated low-dose exposure or abrupt events may lead to similar levels of accumulation. This study contributes to an understanding of norovirus accumulation in oysters and provides suggestions for risk management strategies.
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Chung, H., L. A. Jaykus, G. Lovelace, and M. D. Sobsey. "Bacteriophages and bacteria as indicators of enteric viruses in oysters and their harvest waters." Water Science and Technology 38, no. 12 (December 1, 1998): 37–44. http://dx.doi.org/10.2166/wst.1998.0494.
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Reliable indicators are needed to detect enteric virus contamination of bivalve molluscan shellfish and their harvest waters. Concentrations of male-specific (F+) coliphages, Bacteroides fragilis phages, Salmonella phages and several indicator bacteria in wastewater, estuarine receiving water and its oysters were examined for their ability to predict the presence and levels of faecal contamination and enteric viruses in oysters. Enteric viruses in oysters were detected by cell culture and RT-PCR methods. F+ coliphages, Salmonella phages, B fragilis phages and faecal indicator bacteria (faecal coliforms, E coli, enterococci and Clostridium perfringens) were generally positively associated and were highest in raw sewage and progressively lower in sewage effluent and in receiving waters at increasing distance from the wastewater discharge. Indicator levels in oysters were highest for F+ coliphages and C perfringens. One F+ RNA coliphage serotype (Group II) predominated in the wastewater, receiving water and oysters. Human enteric viruses were detected in 17/31 oyster samples. The levels of most indicators in oysters and water were higher when oysters were enteric virus-positive and lower when oysters were enteric virus-negative. F+ coliphages and C perfringens were the only indicators significantly associated with the presence of enteric viruses in oysters. F+ coliphages and their serotypes are promising indicators of human enteric virus contamination in oysters and their harvest waters.
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Yamashita, T., K. Sakae, Y. Ishihara, and S. Isomura. "A 2-year survey of the prevalence of enteric viral infections in children compared with contamination in locally-harvested oysters." Epidemiology and Infection 108, no. 1 (February 1992): 155–63. http://dx.doi.org/10.1017/s0950268800049608.
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SUMMARYWe studied, for two years, the prevalence of indigenous human enteric viruses in wild oysters gathered each month from the bottom of Mikawa Bay, Aichi Prefecture, Japan. Viruses were detected periodically in 9 out of 54 oyster pools prepared by the acid or polyethylene glycol precipitation method although all these 9 pools met current national bacteriological safety standards. Since most of the serotypes of the enteric viruses detected in the oysters were identical with those of viruses isolated from sick children living in the area, it is suggested that contamination of enteric viruses in the oysters would depend on the prevalence of enteric viral infections in the local inhabitants.
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Rodrigues, Inês C., Nânci Santos-Ferreira, Daniela Silva, Carla Chiquelho da Silva, Ângela S. Inácio, Maria São José Nascimento, and Paulo Martins da Costa. "A One-Year Systematic Study to Assess the Microbiological Profile in Oysters from a Commercial Harvesting Area in Portugal." Microorganisms 11, no. 2 (January 29, 2023): 338. http://dx.doi.org/10.3390/microorganisms11020338.
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As filter-feeding animals farmed in water bodies exposed to anthropogenic influences, oysters can be both useful bioremediators and high-risk foodstuffs, considering that they are typically consumed raw. Understanding the dynamic of bacterial and viral load in Pacific oyster (Crassostrea gigas) tissues, hemolymph, outer shell surface biofilm, and farming water is therefore of great importance for microbiological risk assessment. A one-year survey of oysters collected from a class B production area (Canal de Mira, on the Portuguese western coast) revealed that these bivalve mollusks have a good depurating capacity with regard to bacteria, as Salmonella spp. and viable enterococci were not detected in any oyster flesh (edible portion) samples, despite the fact that these bacteria have regularly been found in the farming waters. Furthermore, the level of Escherichia coli contamination was clearly below the legal limit in oysters reared in a class B area (>230–≤4600 MPN E. coli/100 g). On the contrary, norovirus was repeatedly detected in the digestive glands of oysters sampled in autumn, winter, and spring. However, their presence in farming waters was only detected during winter.
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Green, Timothy J., Chen Yin Walker, Sarah Leduc, Trevor Michalchuk, Joe McAllister, Myron Roth, Jasmine K. Janes, and Erik T. Krogh. "Spatial and Temporal Pattern of Norovirus Dispersal in an Oyster Growing Region in the Northeast Pacific." Viruses 14, no. 4 (April 6, 2022): 762. http://dx.doi.org/10.3390/v14040762.
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Contamination of Pacific oysters, Crassostrea gigas, by human norovirus (HuNoV) is a major constraint to sustainable shellfish farming in coastal waters of the Northeast Pacific. HuNoV is not a marine virus and must originate from a human source. A barrier to effective management is a paucity of data regarding HuNoV dispersal in the marine environment. The main objective of this study was to identify the spatial distribution and persistence of HuNoV in an active shellfish farming region in the Northeast Pacific. Market-size C. gigas were sequentially deployed for two-week intervals at 12 sites during the 2020 winter risk period from January to April. Detection of HuNoV quantification was performed by reverse transcription real-time PCR (RTqPCR) according to method ISO 15216-1:2017, with modifications. RTqPCR did not detect GI HuNoV. The estimated prevalence of GII HuNoV in oyster digestive tissue was 0.8 ± 0.2%. Spatiotemporal analysis revealed that contamination of oysters with GII HuNoV changed through time and space during the surveillance period. A single cluster of oysters contaminated with GII.2 HuNoV was detected in a small craft harbor on 23 April. There was no significant increase in the proportion of positive pools in the next nearest sampling station, indicating that HuNoV is likely to disperse less than 7 km from this non-point source of contamination. Results from this study indicate that HuNoV contamination of coastal waters from non-point sources, such as small craft harbors and urban settings, can pose a significant localised risk to shellfish farming operations in the region.
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BALLESTEROS, Eliete Rodrigues, Vanessa da Costa ANDRADE, Edison BARBIERI, Aline Bartelochi PINTO, Raphaela Sanches de OLIVEIRA, and Ana Júlia Fernandes Cardoso de OLIVEIRA. "Qualidade microbiológica de ostras (Crassostrea sp) e de águas coletadas em cultivos e em bancos naturais de Cananéia (SP)." Boletim do Instituto de Pesca 42, no. 1 (March 30, 2016): 134–44. http://dx.doi.org/10.20950/1678-2305.2016v42n1p134.
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The consumption of marine organisms, especially bivalve molluscs, might affect the human health, once that they concentrate in their tissues, suspended particles, including pathogenic microorganisms. Cananeia region is the largest oyster producer in the state of São Paulo, and in 1999 was founded the Cooperostra (Cooperative), which promotes the oysters depuration process in sterile tanks, leading to reduce and/or eliminate retained substances in their tissues. This study aims (i) evaluate the water quality in the adjacencies of the natural oysters’ beds and during the steps of the depuration process, through the determination of Escherichia coli, total coliforms and thermotolerant coliforms, and (ii)evaluate the contamination of Crassostreasp by Salmonella sp., total coliforms, thermotolerant coliforms and Staphylococcuscoagulase positive, in samples collected at Cooperostra and in natural oysters’beds, assessing the contamination level of the organisms and the efficiency of the depuration process. The results show a reduce of Salmonella sp and coliforms densities in the oysters’ tissues after the depuration process. However, Staphylococcus coagulase positive shown high levels, which may be indicative of handling contamination. The Salmonella sp results were in agreement with RDC n12.
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Miles, M. Scott, Ronald F. Malone, and John E. Supan. "Evaluation of Triploid Oysters as a Tool to assess Short- and Long-term Seafood Contamination of Oil Spill-impacted Areas." International Oil Spill Conference Proceedings 2014, no. 1 (May 1, 2014): 1958–71. http://dx.doi.org/10.7901/2169-3358-2014.1.1958.
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ABSTRACT The objective of this field and laboratory study was to evaluate the use of triploid Eastern oysters, Crassostrea virginica, as a bioindicator of polynuclear aromatic hydrocarbon (PAH) contamination in oil spill-impacted areas. Bivalve mollusks have shown to be valuable tools for assessing the short-term (weeks to months) bioavailability and impact of hydrophobic contaminants following oil and chemical spills. Approximately 1-year after the initial Deepwater Horizon spill, PAH concentrations were measured in sediment and caged oysters at sites within the Northern Barataria Bay. Two (2) seven-week large-scale mesocosm studies were conducted with diploid and triploid oysters to assess the effects of multiple whole South Louisiana crude (SLC) oil concentrations and seasonal water temperature variation on the PAH bioaccumulation and depuration rates within the test populations. Tissue analyses from the mesocosm study showed that PAH concentrations were generally higher and less variable in triploids than diploids. The studies showed that triploid Crassostrea virginica can be an appropriate organism to serve as a bioindicator of PAH contamination as they are abundant, stationary filter-feeders that provide ample tissue for analysis, and accumulate PAHs in response to contamination. Although diploid oysters are more representative of ecological impacts, triploid oysters are the only ploidy to have the capability to accurately assess oil and chemical spill impacts during oyster breeding season.
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Humphrey, T. J., and K. Martin. "Bacteriophage as models for virus removal from Pacific oysters (Crassostrea gigas) during re-laying." Epidemiology and Infection 111, no. 2 (October 1993): 325–35. http://dx.doi.org/10.1017/s0950268800057034.
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SummaryA study was undertaken to examine the feasibility of using naturally-occurring bacteriophages to assess the impact of re-laying on levels of viral contamination inCrassostrea gigas, the Pacific oyster. Two phages were chosen. One, male-specific (F+), was enumerated usingSalmonella typhimurium. The other, a somatic phage, was detected using an, as yet, uncharacterizedEscherichia coli. Investigations, using a variety of re-laying sites, demonstrated that numbers of F+ phage in oyster tissue declined more rapidly than those of somatic phage. For example, in oysters placed in commercially-used sea water ponds, F+ phage reached undetectable levels within 2–3 weeks, whereas somatic phage could still be detected 5 weeks after re-laying. The studies suggest that F+ phage may not be a suitable indicator for virus removal and that somatic phage may be better suited to this role.
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Doyle, A., D. Barataud, A. Gallay, J. M. Thiolet, S. Le Guyaguer, E. Kohli, and V. Vaillant. "Norovirus foodborne outbreaks associated with the consumption of oysters from the Etang de Thau, France, December 2002." Eurosurveillance 9, no. 3 (March 1, 2004): 24–26. http://dx.doi.org/10.2807/esm.09.03.00451-en.
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In January 2003, the Institut de Veille Sanitaire received notification of clusters of gastroenteritis (GE) thought to be associated with consumption of oysters harvested from Etang de Thau in the south of France. At the same time Italy reported an outbreak (200+ cases) associated with oysters from the Etang de Thau. An investigation was carried out to determine the source and vehicle of the outbreaks. Descriptive analysis of reported clusters in France, microbiological analysis of stool and oyster samples, genotyping of noroviruses and an environmental investigation of the Etang de Thau were carried out. A retrospective cohort study was also undertaken among those attending a number of family meals in Paris. Thirteen family clusters in four districts of France (69 cases) could be attributed to the consumption of Thau oysters based on descriptive evidence. Oysters distributed at an office in Paris and consumed at fourteen family meals between 19 and 24 December led to a further outbreak. In this outbreak the attack rate was 21/36 (58%) for Thau oyster consumers and 0/22 for non-consumers (p=0.00002). Noroviruses (genogroups I and II) were found in stool samples from four clusters and oysters from three clusters (including Paris). Environmental investigations revealed heavy rainfall, an overflow of a water purification station and faecal contamination of the Etang de Thau in December. Oysters from the Etang de Thau were responsible for a number of clusters of norovirus GE in winter 2002 in France and also in Italy. High Escherichia Coli levels in Thau water and shellfish led to an official request, mid-December, for oyster purification before distribution. This was not possible, due to lack of purification facilities. This investigation has contributed to a change in the way that shellfish harvesting areas are classified in France.
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Rupnik, Agnieszka, William Doré, Leon Devilly, James Fahy, Amy Fitzpatrick, Wiebke Schmidt, Kevin Hunt, Francis Butler, and Sinéad Keaveney. "Evaluation of Norovirus Reduction in Environmentally Contaminated Pacific Oysters During Laboratory Controlled and Commercial Depuration." Food and Environmental Virology 13, no. 2 (March 2, 2021): 229–40. http://dx.doi.org/10.1007/s12560-021-09464-2.
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AbstractNorovirus 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.
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Lo, Yung-Tsun, Chia-Lan Wang, Bai-Hsung Chen, Chung-Wen Hu, and Chung-Hsi Chou. "Prevalence and Antimicrobial Resistance of Salmonella in Market Raw Oysters in Taiwan." Journal of Food Protection 80, no. 5 (March 30, 2017): 734–39. http://dx.doi.org/10.4315/0362-028x.jfp-16-336.
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ABSTRACT We tested 137 samples of domestic shucked oysters and 114 samples of imported oysters collected from traditional retail markets and supermarkets during 2010 and 2011 in Taiwan for the presence of Salmonella. We obtained a total of 91 Salmonella isolates, representing nine serotypes, from 80 of the domestic samples. We did not find any Salmonella in the imported oysters. The presence of Salmonella contamination tended to be specific to the area from which the oysters were harvested: the Dongshih area had a significantly higher contamination rate (68.8%) than the Budai (20.0%) and Wanggong (9.1%) areas. In addition, the rate of Salmonella contamination was higher in oysters that were packed or sold with water (P < 0.05). The most commonly identified Salmonella serotypes were Saintpaul (26.4%), Newport (22.0%), and Infantis (13.2%). We screened the isolates for susceptibility to nine antimicrobials and compared them genetically by using PCR for the class 1 integron (int1), tetA, tetB, and blaPSE-1 genes. Eighteen isolates (19.8%) were resistant to at least one antimicrobial agent, and the most frequent resistances were those to tetracycline and oxytetracycline (n = 12, 14.3%).We detected the antimicrobial resistance genes int1, tetA, tetB, and blaPSE-1 in 16.5, 26.4, 6.6, and 22.0% of the isolates, respectively. Eleven of the 18 antimicrobial-resistant isolates contained one or two int1 cassettes, suggesting that the presence of int1 is highly correlated with antimicrobial resistance in Salmonella isolates from oysters. The consumption of oysters is increasing in Taiwan, and information related to Salmonella contamination in oysters is rather limited. Our results indicate that raw oyster consumption from retail markets in Taiwan is associated with a human health hazard owing to Salmonella, including multidrug-resistant Salmonella strains.
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Rebelo, M. F., M. C. R. Amaral, and W. C. Pfeiffer. "Oyster condition index in Crassostrea rhizophorae (Guilding, 1828) from a heavy-metal polluted coastal lagoon." Brazilian Journal of Biology 65, no. 2 (May 2005): 345–51. http://dx.doi.org/10.1590/s1519-69842005000200019.
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The condition index (CI) of oysters represents an ecophysiological approach to estimate meat quality and yield in cultured bivalve mollusks. In the present study, the CI of oysters from a heavy-metal polluted bay was analyzed with respect to Zn and Cd contamination in soft tissues, spawning, and polychaete infestation. The CI was calculated through a new technique based on molds made to measure the volume of oyster-shell internal cavities. The higher CI values (over 9 in the dry season) were probably related availability of suspended particles rich in organic matter in the bay, while the rapid reduction in the CI from one season to the next at some stations suggests the effect of spawning. Polychaete infestation was considered low (18.7%) and produced no clear CI effects. The Cd in the oyster tissue collected during the rainy season was weak, although still significantly correlated with the CI (r = -0.36; p < 0.05). All other comparisons of CI and metal concentrations demonstrated a non-significant correlation. The CI variations observed on the temporal and spatial scale were likely to have been caused by availability of organic matter and spawning, rather than spionid infestation or metal body burdens.
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Provost, Keleigh, Brooke A. Dancho, Gulnihal Ozbay, Robert S. Anderson, Gary P. Richards, and David H. Kingsley. "Hemocytes Are Sites of Enteric Virus Persistence within Oysters." Applied and Environmental Microbiology 77, no. 23 (September 23, 2011): 8360–69. http://dx.doi.org/10.1128/aem.06887-11.
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ABSTRACTThe goal of this study was to determine how enteric viruses persist within shellfish tissues. Several lines of novel evidence show that phagocytic blood cells (hemocytes) of Eastern oysters (Crassostrea virginica) play an important role in the retention of virus particles. Our results demonstrated an association of virus contamination with hemocytes but not with hemolymph. Live oysters contaminated overnight with hepatitis A virus (HAV) and murine norovirus (MNV) had 56% and 80% of extractable virus associated with hemocytes, respectively. Transfer of HAV-contaminated hemocytes to naïve (virus-free) oysters resulted in naïve oyster meat testing HAV positive for up to 3 weeks. Acid tolerance of HAV, MNV, poliovirus (PV), and feline calicivirus (FCV) correlated with the ability of each virus to persist within oysters. Using reverse transcription-PCR (RT-PCR) to evaluate persistence of these viruses in oysters, we showed that HAV persisted the longest (>21 days) and was most acid resistant, MNV and PV were less tolerant of acidic pH, persisting for up to 12 days and 1 day, respectively, and FCV did not persist (<1 day) within oysters and was not acid tolerant. This suggests that the ability of a virus to tolerate the acidic conditions typical of phagolysosomal vesicles within hemocytes plays a role in determining virus persistence in shellfish. Evaluating oyster and hemocyte homogenates and live contaminated oysters as a prelude to developing improved viral RNA extraction methods, we found that viruses were extracted more expediently from hemocytes than from whole shellfish tissues and gave similar RT-PCR detection sensitivities.
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Pietri, Ch, B. Hugues, J. M. Crance, D. Puel, C. Cini, and R. Deloince. "Hepatitis a Virus Levels in Shellfish Exposed in a Natural Marine Environment to the Effluent from a Treated Sewage Outfall." Water Science and Technology 20, no. 11-12 (November 1, 1988): 229–34. http://dx.doi.org/10.2166/wst.1988.0289.
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Hepatitis A virus (HAV) contamination studies and cell-culturable virus determination were undertaken on oysters (Crassostrea angulata) and mussels (Mytilus edulis) kept for six months in the sea near the outfall of a sewage treatment plant. Shellfish and seawater samples were collected on 11 occasions at roughly 15-day intervals during this period. A radioimmunoassay revealed HAV contamination indices (P/N ≥ 2.1) in 3 oyster and 6 mussel samples and 1 sea-water sample. When a radiocompetition test was run on these samples, however, specificity was noted in one mussel sample only (P/N = 2.4). Immune electron microscopy showed that HAV particles were present in three effluent samples. Although a frequent demonstration at sometimes high concentrations (326.0 MPNCU/100 ml) in the effluent was observed, no cell-culturable virus were detected in both the shellfish and the seawater. Adenovirus alone were detected in one mussel sample, but not in the effluent. Complementary studies are now being conducted on all samples with an RIA HAV contamination index of P/N ≥ 2.1. The results of this investigation of viral contamination in a natural marine environment and our HAV detection assays underscore the difficulty of determining the true extent of these phenomena.
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Csadek, Isabella, Peter Paulsen, Pia Weidinger, Kathrine H. Bak, Susanne Bauer, Brigitte Pilz, Norbert Nowotny, and Frans J. M. Smulders. "Nitrogen Accumulation in Oyster (Crassostrea gigas) Slurry Exposed to Virucidal Cold Atmospheric Plasma Treatment." Life 11, no. 12 (December 2, 2021): 1333. http://dx.doi.org/10.3390/life11121333.
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Viral contamination of edible bivalves is a major food safety issue. We studied the virucidal effect of a cold atmospheric plasma (CAP) source on two virologically different surrogate viruses [a double-stranded DNA virus (Equid alphaherpesvirus 1, EHV-1), and a single-stranded RNA virus (Bovine coronavirus, BCoV)] suspended in Dulbecco’s Modified Eagle’s Medium (DMEM). A 15 min exposure effectuated a statistically significant immediate reduction in intact BCoV viruses by 2.8 (ozone-dominated plasma, “low power”) or 2.3 log cycles (nitrate-dominated, “high power”) of the initial viral load. The immediate effect of CAP on EHV-1 was less pronounced, with “low power” CAP yielding a 1.4 and “high power” a 1.0 log reduction. We observed a decline in glucose contents in DMEM, which was most probably caused by a Maillard reaction with the amino acids in DMEM. With respect to the application of the virucidal CAP treatment in oyster production, we investigated whether salt water could be sanitized. CAP treatment entailed a significant decline in pH, below the limits acceptable for holding oysters. In oyster slurry (a surrogate for live oysters), CAP exposure resulted in an increase in total nitrogen, and, to a lower extent, in nitrate and nitrite; this was most probably caused by absorption of nitrate from the plasma gas cloud. We could not observe a change in colour, indicative for binding of NOx to haemocyanin, although this would be a reasonable assumption. Further studies are necessary to explore in which form this additional nitrogen is deposited in oyster flesh.
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Le Guyader, Fran�oise S., Sylvain Parnaudeau, Julien Schaeffer, Albert Bosch, Fabienne Loisy, Monique Pommepuy, and Robert L. Atmar. "Detection and Quantification of Noroviruses in Shellfish." Applied and Environmental Microbiology 75, no. 3 (December 1, 2008): 618–24. http://dx.doi.org/10.1128/aem.01507-08.
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ABSTRACT Noroviruses (NoVs) are the most common viral agents of acute gastroenteritis in humans, and high concentrations of NoVs are discharged into the environment. As these viruses are very resistant to inactivation, the sanitary consequences are contamination of food, including molluscan shellfish. There are four major problems with NoV detection in shellfish samples: low levels of virus contamination, the difficulty of efficient virus extraction, the presence of interfering substances that inhibit molecular detection, and NoV genetic variability. The aims of this study were to adapt a kit for use with a method previously shown to be efficient for detection of NoV in shellfish and to use a one step real-time reverse transcription-PCR method with addition of an external viral control. Comparisons of the two methods using bioaccumulated oysters showed that the methods reproducibly detected similar levels of virus in oyster samples. Validation studies using naturally contaminated samples also showed that there was a good correlation between the results of the two methods, and the variability was more attributable to the level of sample contamination. Magnetic silica very efficiently eliminated inhibitors, and use of extraction and amplification controls increased quality assurance. These controls increased the confidence in estimates of NoV concentrations in shellfish samples and strongly supported the conclusion that the results of the method described here reflected the levels of virus contamination in oysters. This approach is important for food safety and is under evaluationfor European regulation.
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LOWTHER, JAMES A., KATHLEEN HENSHILWOOD, and DAVID N. LEES. "Determination of Norovirus Contamination in Oysters from Two Commercial Harvesting Areas over an Extended Period, Using Semiquantitative Real-Time Reverse Transcription PCR." Journal of Food Protection 71, no. 7 (July 1, 2008): 1427–33. http://dx.doi.org/10.4315/0362-028x-71.7.1427.
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The human health risk associated with the consumption of molluscan shellfish grown in sewage-contaminated waters is well established. Noroviruses, which cause gastroenteritis, are the principal agents of shellfish-related illness. Fecal-indicator quality standards based on Escherichia coli are well established in Europe and elsewhere. However, norovirus outbreaks after consumption of shellfish meeting these standards still occur, and the need to improve consumer health protection is well recognized. Alternative approaches proposed include direct monitoring of viral pathogens and the use of alternative indicator organisms capable of providing a better indication of virus risk. This study applies a recently developed TaqMan PCR assay to assess norovirus contamination in shellfish. Comparison was made with E. coli as the existing sanitary standard and a male-specific RNA bacteriophage as a possible alternative. Two commercial pacific oyster (Crassostrea gigas) harvesting areas were monitored over a 31-month period. The results show peaks of norovirus contamination in both areas during winter months, with average levels approximately 17 times higher in oysters sampled October to March than during the remainder of the year, consistent with epidemiological data for the United Kingdom showing oyster-associated illness is confined to winter months. While there was no apparent association with E. coli, an association between levels of norovirus contamination and the male-specific RNA bacteriophage was noted, with average norovirus levels over 40 times higher in samples with male-specific RNA bacteriophage counts of >1,000 PFU/100 g than in samples with <100 PFU/100 g. Overall, these results suggest that norovirus monitoring in shellfish production areas could be an effective strategy for reduction of virus risk.
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Doré, William J., Kathleen Henshilwood, and David N. Lees. "Evaluation of F-Specific RNA Bacteriophage as a Candidate Human Enteric Virus Indicator for Bivalve Molluscan Shellfish." Applied and Environmental Microbiology 66, no. 4 (April 1, 2000): 1280–85. http://dx.doi.org/10.1128/aem.66.4.1280-1285.2000.
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ABSTRACT Escherichia coli is a widely utilized indicator of the sanitary quality of bivalve molluscan shellfish sold for human consumption. However, it is now well documented that shellfish that meet the E. coli standards for human consumption may contain human enteric viruses that cause gastroenteritis and hepatitis. In this study we investigated using F-specific RNA bacteriophage (FRNA bacteriophage) to indicate the likely presence of such viruses in shellfish sold for consumption. FRNA bacteriophage and E. coli levels were determined over a 2-year period for oysters (Crassostrea gigas) harvested from four commercial sites chosen to represent various degrees of sewage pollution. Three sites were classified as category B sites under the relevant European Community (EC) Directive (91/492), which required purification (depuration) of oysters from these sites before sale. One site was classified as a category A site, and oysters from this site could be sold directly without further processing. Samples were tested at the point of sale following commercial processing and packaging. All of the shellfish complied with the mandatory EC E. coli standard (less than 230 per 100 g of shellfish flesh), and the levels of contamination for more than 90% of the shellfish were at or below the level of sensitivity of the assay (20 E. coli MPN per 100 g), which indicated good quality based on this criterion. In contrast, FRNA bacteriophage were frequently detected at levels that exceeded 1,000 PFU per 100 g. High levels of FRNA bacteriophage contamination were strongly associated with harvest area fecal pollution and with shellfish-associated disease outbreaks. Interestingly, FRNA bacteriophage contamination exhibited a marked seasonal trend that was consistent with the trend of oyster-associated gastroenteritis in the United Kingdom. The correlation between FRNA bacteriophage contamination and health risk was investigated further by using a reverse transcription-PCR assay for Norwalk-like virus (NLV). NLV contamination of oysters was detected only at the most polluted site and also exhibited a seasonal trend that was consistent with the trend of FRNA bacteriophage contamination and with the incidence of disease. The results of this study suggest that FRNA bacteriophage could be used as viral indicators for market-ready oysters.
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Ramos, Roberta Juliano, Murilo Anderson Pereira, Letícia Adélia Miotto, Renata D'Aquino Faria, Nelson Silveira Junior, and Cleide Rosana Werneck Vieira. "Ocurrence of Vibrio spp., positive coagulase staphylococci and enteric bacteria in oysters (Crassostrea gigas) harvested in the south bay of Santa Catarina island, Brazil." Food Science and Technology 32, no. 3 (June 7, 2012): 478–84. http://dx.doi.org/10.1590/s0101-20612012005000061.
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The aim of this study was to assess the contamination of oysters (Crassostrea gigas), harvested in six different regions of the South Bay of Santa Catarina Island, with Coliforms at 45 ºC, Escherichia coli, Vibrio spp., positive coagulase staphylococci, and Salmonella sp. over a period of one year. One hundred eighty oyster samples were collected directly from their culture sites and analyzed. Each sample consisted of a pool of 12 oysters. All of the samples analyzed showed absence of Salmonella, 18 (10%) samples showed presence of Escherichia coli, 15 (8.3%) samples were positive for V. alginolyticus, and Vibriocholerae was detected in 4 samples (2.2%). The counts of positive-coagulase staphylococci varied from <10 to 1.9 x 102 CFU.g-1, whereas the counts of Coliforms at 45 ºC and E. coli ranged from <3 to 1.5 x 102 MPN.g-1 and <3 and 4.3 x 10 MPN.g-1, respectively. Counts of V. parahaemolyticus and V. vulnificus ranged between <3 and 7 MPN.g-1, for both microorganisms. This suggests the need for monitoring these Vibrios contamination in oysters. Based on the results of the microbiological assays, the samples analyzed showed acceptable bacteriological quality, i.e., they were within the parameters established by Brazilian Legislation.
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Elsisura, Irish B., and Mary Amor G. Figueroa. "Growth and Yield Performance of Oyster Mushroom Cultivated in Combined Cassava Peels, Coconut Residue and Coffee Waste Substrates." American Journal of Environment and Climate 1, no. 1 (April 8, 2022): 1–11. http://dx.doi.org/10.54536/ajec.v1i1.206.
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The oyster mushroom (Pleurotus ostreatus) is an edible mushroom that belongs to the class of Basidiomycetes. It has reached sufficient market maturity because of its flavor, shelf-life durability, and protein and fiber content. Besides their nutritional, medicinal, and economic value, they may help the country’s agricultural waste management, bridge environmental issues, and contribute to climate change resolution advancements. A study on different varieties of agricultural substrates derived from waste materials such as cassava peels, coconut residue, and coffee waste was investigated and compared to sawdust, the common substrate for oyster mushrooms. The effects of different substrates on the morphological characteristics of P. ostreatus, percent contamination, and yield parameters were recorded and analyzed using the Analysis of Variance in Completely Randomized Design, and their significant results were compared using Tukey’s HSD. Results showed that different substrate mixtures did not significantly influence the morphological characteristics of P. ostreatus. Moreover, sawdust, the common substrate for oyster mushrooms, showed the lowest percent contamination as compared to other substrate mixtures. Contaminants found in cassava substrates include Trichoderma spp., Aspergillus spp., Fusarium spp., Neurospora spp., and Penicillium spp. 80% of cassava peels combined with 10% coconut residue and 10% coffee waste significantly increased the number of fruiting bodies and produced the heaviest fresh weights of oyster mushrooms. Stipe length and pileus diameter were also significantly influenced by this substrate mixture, which is comparable to the common substrate. However, further research on the varying proportions of these substrate mixtures on the performance of oyster mushrooms is recommended.
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Downey, Autumn S., and Thaddeus K. Graczyk. "Maximizing Recovery and Detection of Cryptosporidium parvum Oocysts from Spiked Eastern Oyster (Crassostrea virginica) Tissue Samples." Applied and Environmental Microbiology 73, no. 21 (September 7, 2007): 6910–15. http://dx.doi.org/10.1128/aem.01027-07.
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ABSTRACT Numerous studies have documented the presence of Cryptosporidium parvum, an anthropozoonotic enteric parasite, in molluscan shellfish harvested for commercial purposes. Getting accurate estimates of Cryptosporidium contamination levels in molluscan shellfish is difficult because recovery efficiencies are dependent on the isolation method used. Such estimates are important for determining the human health risks posed by consumption of contaminated shellfish. In the present study, oocyst recovery was compared for multiple methods used to isolate Cryptosporidium parvum oocysts from oysters (Crassostrea virginica) after exposure to contaminated water for 24 h. The immunomagnetic separation (IMS) and immunofluorescent antibody procedures from Environmental Protection Agency method 1623 were adapted for these purposes. Recovery efficiencies for the different methods were also determined using oyster tissue homogenate and hemolymph spiked with oocysts. There were significant differences in recovery efficiency among the different treatment groups (P < 0.05). We observed the highest recovery efficiency (i.e., 51%) from spiked samples when hemolymph was kept separate during the homogenization of the whole oyster meat but was then added to the pellet following diethyl ether extraction of the homogenate, prior to IMS. Using this processing method, as few as 10 oocysts could be detected in a spiked homogenate sample by nested PCR. In the absence of water quality indicators that correlate with Cryptosporidium contamination levels, assessment of shellfish safety may rely on accurate quantification of oocyst loads, necessitating the use of processing methods that maximize oocyst recovery. The results from this study have important implications for regulatory agencies charged with determining the safety of molluscan shellfish for human consumption.
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Shen, Xiao Sheng, Bei Lei Qian, Wei Hua Wu, You Qiong Cai, and Cheng Chu Liu. "Elimination of Vibrio parahaemolyticus Contamination in Shucked Oysters (Crassostrea plicatula) to with Natural Antimicrobial Agents TeaPolyphenols." Advanced Materials Research 320 (August 2011): 427–33. http://dx.doi.org/10.4028/www.scientific.net/amr.320.427.
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In this study, the survival of Vibrio parahaemolyticus in suspension in the presence of tea-polyphenols for 6h was first examined. The shucked oysters containing V. parahaemolyticus then were exposed to 2048μg/mL , 1024 μg/mL and 512 μg/mL tea-polyphenols for 4h and the population ofV. parahaemolyticusin shucked oysters was determined every 1h. In addition, shucked oysters containingV. parahaemolyticusexposed into the dose of 1024 μg/mL tea-polyphenols were held at various temperature (0, 5, and 20°C) to examine survival ofV. parahaemolyticusevery 6h till 24h. Populations ofV. parahaemolyticusinoysterwere determined using 3-tube most probable number (MPN) method. The study found that the MIC of tea-polyphenols to Vibrio parahaemolyticus suspension is 1024 μg/mL; when exposed to 2048 μg/mL, 1024 μg/mLand 512μg/mL tea-polyphenols for 4h, the population ofV. parahaemolyticusinshucked oysters decreased by 3.29,2.43 and 1.84 Log10MPN/g respectively; 0, 5 and 20°C,1024μg/mL tea-polyphenols can decrease the population of V. parahaemolyticusinshucked by 4.10, 3.32 and 3.00LogMPN/g at 24thh. Sensory analysis showed that treatments of tea-polyphenols at concentrations 1024μg/mL did not cause negative effects on taste of oyster meat. These results indicated that tea-polyphenols have bactericidal effects againstV. parahaemolyticusand can be applied to shucked oysters to reduce contamination of V. parahaemolyticus.
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Tam, S. Y. K., and C. S. Mok. "Metallic contamination in oyster and other seafood in Hong Kong." Food Additives and Contaminants 8, no. 3 (May 1991): 333–42. http://dx.doi.org/10.1080/02652039109373982.
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Alzieu, C. L., J. Sanjuan, J. P. Deltreil, and M. Borel. "Tin contamination in Arcachon Bay: Effects on oyster shell anomalies." Marine Pollution Bulletin 17, no. 11 (November 1986): 494–98. http://dx.doi.org/10.1016/0025-326x(86)90636-3.
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Grodzki, Marco, Joanna Ollivier, Jean-Claude Le Saux, Jean-Côme Piquet, Mathilde Noyer, and Françoise S. Le Guyader. "Impact of Xynthia Tempest on Viral Contamination of Shellfish." Applied and Environmental Microbiology 78, no. 9 (February 17, 2012): 3508–11. http://dx.doi.org/10.1128/aem.07604-11.
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ABSTRACTViral contamination in oyster and mussel samples was evaluated after a massive storm with hurricane wind named “Xynthia tempest” destroyed a number of sewage treatment plants in an area harboring many shellfish farms. Although up to 90% of samples were found to be contaminated 2 days after the disaster, detected viral concentrations were low. A 1-month follow-up showed a rapid decrease in the number of positive samples, even for norovirus.
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Widiwurjani, Ida Retno Mulyani, Ilmatus Sa’diyah, and N. K. Sari. "Potential Of Various Types of Media for Breeding Oyster Mushroom F2." E3S Web of Conferences 328 (2021): 08015. http://dx.doi.org/10.1051/e3sconf/202132808015.
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This research was conducted at the Laboratory of Biotechnology 1 and Farmers' Land in Karanganyar village, Poncokusumo, Malang. The materials used in this study were white oyster mushroom F1 seeds, 70% alcohol, soybean seeds, corn seeds, rice, sawdust, rice bran and mushroom baglog. This study used an experimental design, namely Completely Randomized Design (CRD) with 8 treatment levels B1 = corn kernels (100%), B2 = soybean seeds (100%), B3 = rice (100%), B4 = sawdust (100%), B5 = corn kernels (50%) + sawdust (40%) + rice bran (10%). Parameters observed were height of Mycelium-covered Media (cm), Mycelium Growth Speed (cm/day), Contamination Occurrence Percentage (%). The average yield of the highest seedling height was 12.79 cm in treatment B8. The parameter of mycelium growth rate in B8 treatment had the fastest growth rate of 1.82 cm/ha. The lowest contamination was found in treatment B5, B6 by 4% and B7 by 20%. Treatment B3, B4 and B8 did not experience contamination.
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Qureshi, Ateef A., Adel Mahasneh, Hashim Al-Sayed, Amal Al-Buflasa, and Mariam Al-Shuaibi. "Fecal Pollution of Pearl Oyster (Pinctada radiata)." Water Science and Technology 27, no. 3-4 (February 1, 1993): 35–39. http://dx.doi.org/10.2166/wst.1993.0317.
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The physical parameters of the five sampling sites, such as the depth of the oyster beds, ranged from <1 to 20m; salinity, 40.98 to 56.75 g/L; pH, 7.76 to 7.95; temperature, 20.0 to 27.38°C; and dissolved oxygen, 5.60 to 5.96 mg/L. A wide range of distribution of the indicators of fecal pollution; total coliforms, 3.48 × 103 to 8.0 × 105/g; fecal coliforms, 2.97 × 102 to 3.2 × 105/g; and an enteric virus population of 0 to 4.66 virions/gof oyster meat, were detected. These observations indicate alarming levels of fecal contamination and waiiant serious concentrated efforts to contain the pollution hazards in the coastal waters.
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Fernández-Delgado, Milagro, Monica Contreras, María Alexandra García-Amado, Pulchérie Gueneau, and Paula Suárez. "Occurrence of Proteus mirabilis associated with two species of venezuelan oysters." Revista do Instituto de Medicina Tropical de São Paulo 49, no. 6 (December 2007): 355–59. http://dx.doi.org/10.1590/s0036-46652007000600004.
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The fecal contamination of raw seafood by indicators and opportunistic pathogenic microorganisms represents a public health concern. The objective of this study was to investigate the presence of enteric bacteria colonizing oysters collected from a Venezuelan touristic area. Oyster samples were collected at the northwestern coast of Venezuela and local salinity, pH, temperature, and dissolved oxygen of seawater were recorded. Total and fecal coliforms were measured for the assessment of the microbiological quality of water and oysters, using the Multiple Tube Fermentation technique. Analyses were made using cultures and 16S rRNA gene sequencing. Diverse enrichment and selective culture methods were used to isolate enteric bacteria. We obtained pure cultures of Gram-negative straight rods with fimbriae from Isognomon alatus and Crassostrea rhizophorae. Our results show that P. mirabilis was predominant under our culture conditions. We confirmed the identity of the cultures by biochemical tests, 16S rRNA gene sequencing, and data analysis. Other enterobacteria such as Escherichia coli, Morganella morganii and Klebsiella pneumoniae were also isolated from seawater and oysters. The presence of pathogenic bacteria in oysters could have serious epidemiological implications and a potential human health risk associated with consumption of raw seafood.
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THEBAULT, A., J. C. LE SAUX, M. POMMEPUY, S. LE GUYADER, R. LAILLER, and J. B. DENIS. "Quantitative Approach of Risk Management Strategies for Hepatitis A Virus–Contaminated Oyster Production Areas." Journal of Food Protection 75, no. 7 (July 1, 2012): 1249–57. http://dx.doi.org/10.4315/0362-028x.jfp-11-411.
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It is not yet known whether using the new molecular tools to monitor hepatitis A virus (HAV) in shellfish production areas could be useful for improving food safety. HAV contamination can be acute in coastal areas, such as Brittany, France, where outbreaks of hepatitis A have already occurred and have been linked to the consumption of raw shellfish. A quantitative probabilistic approach was carried out to estimate the mean annual risk of hepatitis A in an adult population of raw oyster consumers. Two hypothetical scenarios of contamination were considered, the first for a rare and brief event and the second for regular and prolonged episodes of contamination. Fourteen monitoring and management strategies were simulated. Their effects were assessed by the relative risk reduction in mean annual risk. The duration of closure after abnormal detection in the shellfish area was also considered. Among the strategies tested, results show that monthly molecular reverse transcription PCR monitoring of HAV is more useful than bacterial surveys. In terms of management measures, early closure of the shellfish area without waiting for confirmatory analysis was shown to be the most efficient strategy. When contamination is very short-lived and homogeneous in the shellfish production area, waiting for three negative results before reopening the area for harvest is time wasting. When contamination is not well identified or if contamination is heterogeneous, it can be harmful not to wait for three negative results. In addition, any preventive measures, such as improving sewage treatment or producing shellfish in safer areas, that can reduce contamination by at least 2 log units are more efficient and less costly. Finally we show that controlling and managing transferred shellfish are useful and can play an important role in preventing cases. Qualitative results from HAV monitoring can advantageously supplement other measures that improve the safety of shellfish products in exposed areas.
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PARKER, ROGER W., ELLEN M. MAURER, A. BILL CHILDERS, and DONALD H. LEWISI. "Effect of Frozen Storage and Vacuum-Packaging on Survival of Vibrio Vulnificus in Gulf Coast Oysters (Crassostrea virginica)." Journal of Food Protection 57, no. 7 (July 1, 1994): 604–6. http://dx.doi.org/10.4315/0362-028x-57.7.604.
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Vibrio vulnificus contamination of raw oysters is a serious public health hazard, therefore, it is necessary to investigate the persistence of V. vulnificus in harvested and stored oysters. For this study, triplicate oyster samples were split into four treatment groups: control, normal-packaged; control, vacuum-packaged; inoculated, normal-packaged; and inoculated, vacuum-packaged. Oysters in the inoculated groups were individually injected with V. vulnificus to a level of approximately 1 × 106 CFU/g. Control oysters were already naturally contaminated to a level of approximately 1 × 104 CFU/g. Oysters were then packaged, frozen and stored at −20°C. On day 0 and days 7, 14, 30 and 70 post-freezing, concentrations of total aerobic bacteria and V. vulnificus were determined using a 3-tube most probable number (MPN) estimation from enrichment Alkaline Peptone Water tubes with subsequent presumptive V. vulnificus growth on modified Cellobiose-Polymyxin B-Colistin agar. Length of frozen storage had a significant effect on decreasing total aerobic bacteria (from approximately 106 CFU/g to approximately 102.5 CFU/g) and V. vulnificus (from approximately 105 CFU/g to approximately 101 CFU/g). Also, vacuum-packaged samples showed significantly lower concentrations of V. vulnificus over the length of the study than did the normal-sealed samples.
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Drouaz, Najoua, Julien Schaeffer, Tibor Farkas, Jacques Le Pendu, and Françoise S. Le Guyader. "Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters." Applied and Environmental Microbiology 81, no. 15 (May 29, 2015): 5249–56. http://dx.doi.org/10.1128/aem.01067-15.
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ABSTRACTOyster contamination by noroviruses is an important health and economic problem. The present study aimed to compare the behaviors of Norwalk virus (the prototype genogroup I norovirus) and two culturable viruses: Tulane virus and mengovirus. After bioaccumulation, tissue distributions were quite similar for Norwalk virus and Tulane virus, with the majority of viral particles detected in digestive tissues, while mengovirus was detected in large amounts in the gills and mantle as well as in digestive tissues. The levels of persistence of all three viruses over 8 days were comparable, but clear differences were observed over longer periods, with Norwalk and Tulane viruses displaying rather similar half-lives, unlike mengovirus, which was cleared more rapidly. These results indicate that Tulane virus may be a good surrogate for studying norovirus behavior in oysters, and they confirm the prolonged persistence of Norwalk virus in oyster tissues.
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Graczyk, Thaddeus K., Autumn S. Girouard, Leena Tamang, Sharon P. Nappier, and Kellogg J. Schwab. "Recovery, Bioaccumulation, and Inactivation of Human Waterborne Pathogens by the Chesapeake Bay Nonnative Oyster, Crassostrea ariakensis." Applied and Environmental Microbiology 72, no. 5 (May 2006): 3390–95. http://dx.doi.org/10.1128/aem.72.5.3390-3395.2006.
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ABSTRACT The introduction of nonnative oysters (i.e., Crassostrea ariakensis) into the Chesapeake Bay has been proposed as necessary for the restoration of the oyster industry; however, nothing is known about the public health risks related to contamination of these oysters with human pathogens. Commercial market-size C. ariakensis triploids were maintained in large marine tanks with water of low (8-ppt), medium (12-ppt), and high (20-ppt) salinities spiked with 1.0 � 105 transmissive stages of the following human pathogens: Cryptosporidium parvum oocysts, Giardia lamblia cysts, and microsporidian spores (i.e., Encephalitozoon intestinalis, Encephalitozoon hellem, and Enterocytozoon bieneusi). Viable oocysts and spores were still detected in oysters on day 33 post-water inoculation (pwi), and cysts were detected on day 14 pwi. The recovery, bioaccumulation, depuration, and inactivation rates of human waterborne pathogens by C. ariakensis triploids were driven by salinity and were optimal in medium- and high-salinity water. The concentration of human pathogens from ambient water by C. ariakensis and the retention of these pathogens without (or with minimal) inactivation and a very low depuration rate provide evidence that these oysters may present a public health threat upon entering the human food chain, if harvested from polluted water. This conclusion is reinforced by the concentration of waterborne pathogens used in the present study, which was representative of levels of infectious agents in surface waters, including the Chesapeake Bay. Aquacultures of nonnative oysters in the Chesapeake Bay will provide excellent ecological services in regard to efficient cleaning of human-infectious agents from the estuarine waters.
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MONTANHINI, MAIKE TAÍS MAZIERO, and ROBERTO MONTANHINI NETO. "Changes in the Microbiological Quality of Mangrove Oysters (Crassostrea brasiliana) during Different Storage Conditions." Journal of Food Protection 78, no. 1 (January 1, 2015): 164–71. http://dx.doi.org/10.4315/0362-028x.jfp-14-255.
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This study aimed to determine the effect of temperature and period of postharvest storage on the microbiological quality and shelf life of raw mangrove oysters, Crassostrea brasiliana. A total of 150 dozen oysters were collected directly from the points of extraction or cultivation in southern Brazil, and in the laboratory, they were stored raw at 5, 10, 15, 20, and 25°C for 1, 4, 8, 11, and 15 days. On each of these days, the oysters were subjected to microbiological analyses of aerobic mesophilic count, total coliforms, enterococci, Escherichia coli, Staphylococcus aureus, and Salmonella. None of the tested samples under any storage condition showed contamination levels above those allowed by Brazilian legislation for E. coli, S. aureus, and Salmonella, and there was no change (P > 0.05) in the counts of these microorganisms due to the temperature and/or period of oyster storage. Counts of enterococci and total coliforms showed a tendency to increase (P < 0.05) among the different temperatures tested. Raw mangrove oysters remain in safe microbiological conditions for consumption up to 8 days after harvesting, regardless of temperature, and their shelf life may be extended to 15 days if they are stored at temperatures not exceeding 15°C.
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Amado-Filho, GM, LT Salgado, MF Rebelo, CE Rezende, CS Karez, and WC Pfeiffer. "Heavy metals in benthic organisms from Todos os Santos Bay, Brazil." Brazilian Journal of Biology 68, no. 1 (February 2008): 95–100. http://dx.doi.org/10.1590/s1519-69842008000100013.
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The marine ecosystems of Todos os Santos Bay (TSB, The State of Bahia, Brazil) have been impacted by the presence on its coast of a large metropolitan area as well as of chemical and petrochemical activities. Despite its ecological importance, there is a lack of scientific information concerning metal contamination in TSB marine biota. Thus, we analyzed concentrations of metals in four species of marine benthic organisms (two seaweeds, Padina gymnospora and Sargassum sp. one seagrass, Halodule wrightii and one oyster, Crassostrea rhizophorae) in three sites from the TSB region that have been most affected by industrial activities. The concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined by Atomic Absorption Spectrophometry. The obtained data indicates that cadmium and copper in seaweeds, oysters and seagrass, as well as Ni concentrations in oysters, were in range of contaminated coastal areas. Cadmium and copper are available to organisms through suspended particles, dissolved fraction of water column and bottom sediment interstitial water. As oysters and other mollusks are used as food sources by the local population, the metal levels found in oysters in TSB may constitute a health risk for this population. Our results suggest implanting a heavy metals biomonitoring program in the TSB marine ecosystems.