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Auswahl der wissenschaftlichen Literatur zum Thema „Oyster contamination“
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Zeitschriftenartikel zum Thema "Oyster contamination"
1
COLE, MARY TOWNSEND, MARILYN B. KILGEN und CAMERON R. HACKNEY. „Evaluation of Methods for Extraction of Enteric Virus from Louisiana Oysters“. Journal of Food Protection 49, Nr. 8 (01.08.1986): 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.
2
COOK, DAVID W., und R. D. ELLENDER. „Relaying to Decrease the Concentration of Oyster-Associated Pathogens“. Journal of Food Protection 49, Nr. 3 (01.03.1986): 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.
3
Boher, S., und L. Schwartzbrod. „Study of Viral Purification of Oysters“. Water Science and Technology 27, Nr. 3-4 (01.02.1993): 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 und 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, Nr. 9 (10.09.2018): 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 und CLAUDIA HÄSE. „Refrigerated Seawater Depuration for Reducing Vibrio parahaemolyticus Contamination in Pacific Oyster (Crassostrea gigas)“. Journal of Food Protection 73, Nr. 6 (01.06.2010): 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, und Edward R. Atwill. „Modelling of Indicator Escherichia coli Contamination in Sentinel Oysters and Estuarine Water“. International Journal of Environmental Research and Public Health 16, Nr. 11 (04.06.2019): 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 und Bianca Mendes Maciel. „Microbiological Quality and Prevalence of β-Lactam Antibiotic Resistance Genes in Oysters (Crassostrea rhizophorae)“. Journal of Food Protection 80, Nr. 3 (16.02.2017): 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 und Jacques Le Pendu. „Bovine Norovirus: Carbohydrate Ligand, Environmental Contamination, and Potential Cross-Species Transmission via Oysters“. Applied and Environmental Microbiology 76, Nr. 19 (13.08.2010): 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., und LYNN A. JOENS. „Prevalence and Characterization of Salmonella Serovars Isolated from Oysters Served Raw in Restaurants“. Journal of Food Protection 74, Nr. 6 (01.06.2011): 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 und Andrew S. Ball. „Are Sterols Useful for the Identification of Sources of Faecal Contamination in Shellfish? A Case Study“. Water 12, Nr. 11 (02.11.2020): 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.
Dissertationen zum Thema "Oyster contamination"
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Strady, Emilie. „Mécanismes biogéochimiques de la contamination des huîtres Crassostrea gigas en Cadmium en baie de Marennes Oléron“. Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14060/document.
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La baie de Marennes Oléron, premier site ostréicole français, est influencée par la pollution polymétallique historique de l’estuaire de la Gironde avec des concentrations en cadmium dans les huîtres proches de la limite de consommation européenne (RNO 2006; 5 μg.g-1 ps, ECNo.466/2001). Ces travaux de recherche pluridisciplinaires ont pour objectif de caractériser le comportement des ETM en zone côtière et les mécanismes de contamination en ETM des huîtres, spécifiquement en Cd, dans la baie de Marennes Oléron. Pour cela, sept missions océanographiques en période contrastée ont permis de caractériser la spéciation des ETM à l’embouchure des estuaires de la Charente et de la Gironde ainsi qu’au Pertuis de Maumusson.Une étude spatio-temporelle complémentaire des sédiments de surface de la baie de Marennes Oléron a montré un enrichissement des sédiments de surface en Cd dans la zone sud baie,confirmant la connexion des eaux girondines et l’apport en Cd particulaire à la baie par le Pertuis de Maumusson. Cette zone sud a ainsi été choisie pour mener une transplantation d’huîtres pendant trois mois. L’hydrodynamique régionale, observée par imagerie satellite, a présenté unrôle important dans la distribution et la variation temporelle des concentrations en Cd dissous et particulaires minérales de la baie. La bioaccumulation en Cd des différents organes d’huîtres cultivées sur table a été plus importante que celle des huîtres cultivées directement sur le sol,suggérant le faible rôle de la diffusion de Cd par la remise en suspension des sédiments de surface et du microphytobenthos sur la bioaccumulation. De plus, le temps d’immersion étant relativement proche entre les deux conditions, nous suggérons que la voie trophique via le plankton pélagique participe à la contamination des huîtres en plus de la voie directe. Cette contribution de la voie trophique a été confirmée lors d’expérimentations en conditions contrôlées en laboratoire par le développement d’une méthode de traçage simultané des voies de contamination directe et trophique par ajouts d’isotopes stables de Cd, conduites pour des concentrations 10 fois supérieures à l’environnement et des concentrations réalistes observées en baie de Marennes Oléron (40 ng.l-1 et ~0.7 mg.kg-1)The Marennes-Oléron Bay, hosting the largest oyster production in France, is influenced by thehistoric polymetallic pollution of the Gironde Estuary, with cadmium levels in oysters close tothe consumption limit level (5 μg.g-1 dw, EC No.466/2001). The aim of this pluridisciplinarywork was to characterize the behaviour of trace metals in the coastal zone and the mechanisms ofCd contamination in oysters in the Marennes Oléron Bay. Seven oceanographic cruises wereconducted during contrasting season to characterize trace metals behaviour and speciation in theGironde and Charente estuaries and the coastal zone. Then, a spatial and temporal study of tracemetals in the surface sediments of the Marennes-Oléron Bay showed punctual Cd-enrichedsediments in the southern part, reflecting the connexion with the Gironde waters and theparticulate Cd inputs via the Maumusson inlet. Thus, this area was chosen to study Cdbioaccumulation in oysters over a three months transplantation. The regional hydrodynamic,observed by satellite images, played an important role on Cd speciation and the temporalvariability of dissolved and particulate Cd concentrations. Cadmium bioaccumulation in organsof oysters reared on tables at 60 cm height was more important than in oysters reared near thesediment, suggesting the absence of Cd released during tidal suspension from sediment andmicrophytobenthos. Furthermore, as the immersion time was closed between the two rearingconditions, we suggested Cd bioaccumulation via the direct pathway and also via trophicpathway of contamination by pelagic plankton ingestion. This trophic pathway of Cdcontamination was validated during laboratory experiments using a simultaneous tracing of Cddirect and trophic pathways in oysters by stable isotope spikes at concencentrations 10-foldhigher than the Gironde Estuary and at realistic concentrations observed in the Marennes-OléronBay
2
Geary, Phillip M., University of Western Sydney, of Science Technology and Environment College und of Science Food and Horticulture School. „On-site system effluent source tracking using geochemical and microbial tracers in a coastal catchment“. THESIS_CSTE_SFH_Geary_P.xml, 2004. http://handle.uws.edu.au:8081/1959.7/566.
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The principal aims of this thesis were to examine whether there were hydraulic links between individual on-site wastewater systems in sandy soils at Salt Ash and the Tilgerry Creek estuary near Port Stephens, New South Wales, and whether the chemical and microbiological contaminants from on-site systems could reach surface and groundwaters, and possibly lead to impacts on estuarine oyster growing waters. The research outcomes are contained within the thesis and in four refereed papers presented at conferences, and which have been subsequently published, or are in press. Copies of each of these papers are contained within the thesis Appendices. The presence of faecal contamination from domestic systems in the estuary, and surface drains in particular, has been confirmed by work contained in this thesis. The potential level of risk to human health from the consumption of contaminated oysters is, however, regarded as very low, although an assessment of health risk using established microbial assessment models has not been undertakenDoctor of Philosophy (PhD)
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Geary, Phillip M. „On-site system effluent source tracking using geochemical and microbial tracers in a coastal catchment“. Thesis, View thesis, 2004. http://handle.uws.edu.au:8081/1959.7/566.
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The principal aims of this thesis were to examine whether there were hydraulic links between individual on-site wastewater systems in sandy soils at Salt Ash and the Tilgerry Creek estuary near Port Stephens, New South Wales, and whether the chemical and microbiological contaminants from on-site systems could reach surface and groundwaters, and possibly lead to impacts on estuarine oyster growing waters. The research outcomes are contained within the thesis and in four refereed papers presented at conferences, and which have been subsequently published, or are in press. Copies of each of these papers are contained within the thesis Appendices. The presence of faecal contamination from domestic systems in the estuary, and surface drains in particular, has been confirmed by work contained in this thesis. The potential level of risk to human health from the consumption of contaminated oysters is, however, regarded as very low, although an assessment of health risk using established microbial assessment models has not been undertaken
4
McMenemy, Paul. „A mathematical framework for designing and evaluating control strategies for water- & food-borne pathogens : a norovirus case study“. Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/25453.
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Norovirus (NoV) is a significant cause of gastroenteritis globally, and the consumption of oysters is frequently linked to outbreaks. Depuration is the principle means employed to reduce levels of potentially harmful agents or toxins in shellfish. The aim of this thesis is to construct mathematical models which can describe the depuration dynamics of water-borne pathogens, and specifically examine the dynamics of NoV during depuration for a population shellfish. Legislation is currently under consideration within the EU by the Directorate-General for Health and Consumers (DG SANCO) to limit the maximum level of NoV that consumers are exposed to via this route. Therefore it is important to the utility of the thesis that any models constructed should incorporate control measures which could be used to implement minimum NoV levels. Doing so allowed calculation of minimum depuration times that would be required to adhere to the control measures incorporated into the models. In addition to modelling the impact on pathogens during the depuration, we wished to gain some insight into how the variability, and not just the mean levels, of water-borne pathogens can be as important with respect to the length of depuration required to minimise any food safety risks to the consumer. This proved difficult in the absence of any data sets that can be used to calculate variability measures, as little data is currently available to inform these values for NoV. However, our modelling techniques were able to calculate an upper limit on the variability of water-borne pathogens that can be well approximated by lognormal distributions. Finally we construct a model which provided linkage between the depuration process and the accretion of pathogens by shellfish while still within farming waters. This model proposed that the pulses of untreated waste waters released by sewage treatment works due to high levels of rainfall would be transmitted into shellfish whilst filter-feeding.
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Brake, F. „Minimising the risk of norovirus contamination in Australian commercial oysters“. Thesis, 2016. https://eprints.utas.edu.au/23021/3/Brake_whole_thesis_ex_pub_mat.pdf.
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Outbreaks of human gastroenteritis caused by norovirus (NoV)-contaminated oysters occur
worldwide and have periodically been linked to the consumption of Australian oysters.
Contamination with NoV can occur when human excrement (faeces and vomit) containing the
virus flows into oyster growing areas. Minimal data about the occurrence of NoV in Australian
oysters was available at the commencement of this thesis due to the expense involved in testing
oysters for viruses because no Australian commercial laboratories had the capacity to perform
the test. To that time, all Australian samples were tested in New Zealand.
The aim of this Thesis was to establish an informed strategy for minimising the risk of NoV in
commercial Australian oysters. To collect the NoV data, a sensitive and accurate method to
detect NoV was adopted in this study and validated for Australian oysters and conditions.
Epidemiological evidence suggests that the occurrence of NoV in Australian oysters is low;
therefore a sampling regime for the detection of NoV at low occurrence and concentration in
oysters was designed. Using this sampling programme, NoV was detected in oysters (8.3%, n =
163) from a harvest area that had been associated with 2 NoV illness outbreaks. The results
showed the need for a comprehensive sampling regime to ensure the detection of NoV.
To address the lack of systematically collected data on the occurrence of NoV in Australian
growing areas and due to the impending imposition of international standards for NoV in
Australia, a survey was conducted. This involved the collection of oysters from two
geographically distinct oyster growing areas on four occasions from each of the three main
oyster producing States in Australia and testing samples for NoV and E. coli (n = 120). The
growing areas selected were considered by Australian shellfish authorities to be the most
compromised in those States with respect to the potential for human faecal contamination, as
identified by shoreline surveys.
NoV GII was detected in two samples (1.7%) but NoV GI was not detected. Some of the
samples were found to have more than the guidance concentration of 230 E. coli per 100 g of
shellfish flesh but these samples did not contain detectable concentrations of NoV. These results
reinforce epidemiological data suggesting that NoV contamination of commercially produced
Australian oysters is rare.
There is minimal data about NoV dispersal in waterways following sewage overflows.
The persistence of NoV in Sydney Rock oysters (SRO) following sewage overflows was also
unknown. These knowledge gaps were addressed by strategically placing SRO in an estuary
downstream from a sewage pump station known to overflow periodically and initiating sampling
after an overflow event. After the event NoV GII was detected up to 5.29 km downstream and
persisted in SRO closest to the pump station outfall for 42 days. NoV GII concentrations
decreased significantly over time; a reduction rate of 8.5% per day was observed in oysters
located at two sites near the outfall (p<0.001). Five days after the overflow, NoV GII
concentrations were found to decrease significantly as a function of distance at a rate of 5.8% per
km (p<0.001). The decline in E. coli concentration with distance was 20.1% per km (p<0.001).
NoV GI and Hepatitis A virus were not detected. A comparison of NoV GII reduction rates from
oysters over time, derived from 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.
In the final phase of the project, an investigation of risk management options for Australian
commercial oyster harvest areas to protect oyster consumers from NoV was conducted. The
result, a culmination of data and research, is a combination of strategies recommended for
minimising the risk of NoV prevalence in Australian oysters. It was found that the risk is real, as
demonstrated by the occurrence of 1-2 outbreaks of NoV illness associated with oysters
annually. This was supported by the findings of a NoV contamination rate of 1.7% of oysters
from Australian growing areas. Recommendations were made for risk management strategies to
prevent contamination of oyster growing areas and to enable rapid detection and notification of
contamination events when they occur.
It was found that communication between local councils, water utility operators and shellfish
authorities regarding reporting sewage spills and the condition of potential sources of sewage
spills (i.e. on-site sewage management systems (OSMS)) was lacking. A theoretical NoV
contamination event in oyster growing areas was considered, showing that it was possible for a
small human faecal mishap to cause illness in oyster consumers. Recommendations for a riskbased
virus monitoring programme are proposed, including: regulation of OSMS by local
councils; workshops on water quality to stimulate increased communication between
Environmental Health Officers and shellfish authorities; upgrading sewage treatment plants
where the effluent flows into oyster growing areas; mandatory dye studies of STP effluent flows
and potential sources of sewage overflows for each growing area to enable more effective closure times and delineation of the impacted area closed for harvesting; ASQAP to include
guidance to put local management committees in place for each growing area, ASQAP to include
guidance for portable toilets to be on oyster harvesting boats, and the development of an
alternative indicator for NoV other than faecal coliforms i.e. bacteriophage testing.
The results of this Thesis will improve NoV risk management strategies used by shellfish
authorities to protect the Australian oyster consumer and help to ensure that future control
measures are commensurate with the risk associated with the growing area rather than requiring
mandatory end product testing regimes for all areas.
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Chae, Minjung. „Low-temperature post-harvest processing for reducing Vibrio parahaemolyticus and Vibrio vulnificus in raw oysters“. Thesis, 2007. http://hdl.handle.net/1957/5705.
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Oysters are filter-feeding bivalves, which filter water for nutrients and often accumulate contaminants and human pathogens such as Vibrio parahaemolyticus and Vibrio vulnificus naturally occurring in the marine environment. These naturally occurring pathogens have been frequently isolated from raw shellfish, particularly oyster, in the United States and are recognized as the leading causes of human gastroenteritis associated with seafood consumption. Human illness caused by consumption of raw oyster contaminated with V. parahaemolyticus and Vibrio vulnificus typically results in reduced sales of oysters and a consequent significant financial burden for the producers. The United States produces more than 27 million pounds of oysters each year with a large portion of them being produced from the coastal water of the Gulf of Mexico. It is estimated that 20 million Americans eat raw shellfish and consumption of raw oyster
is responsible for about 95% of all deaths associated with seafood consumption in the U.S., making raw oysters one of the most hazardous seafoods. Several post-harvest processes, including low temperature pasteurization, freezing, high pressure processing and irradiation, have been reported capable of reducing Vibrio contamination in raw oysters. However, most of them require either a significant amount of initial investment or operation costs, and oysters are often killed during processing. Cost-effective post-harvest processing for reducing V. parahaemolyticus in raw oysters without significant adverse effects on the oysters remains to be developed. This study was conducted to determine impacts of low-temperature (15, 10 and 5°C) depuration and frozen storage on reducing V. parahaemolyticus and V. vulnificus in raw oysters. Depuration of the Gulf oyster (Crassostrea virginica) with electrolyzed oxidizing (EO) water (chlorine, 30 ppm; pH 2.82; oxidation-reduction potential, 1,131mV) containing 3% NaCl was found ineffective on reducing both V. parahaemolyticus and V. vulnificus in the oysters. Reductions of V. parahaemolyticus and V. vulnificus in oyster after 48 h of EO water depuration at 22°C were limited to 0.7 and 1.4 log MPN/g, respectively. Depuration with EO water at lower temperatures did not enhance reductions of Vibrio in the oysters. Greater reductions of V. parahaemolyticus (1.2 log MPN/g) and V. vulnificus (2.0 log MPN/g) were observed when the oysters were depurated with artificial seawater (ASW) at room temperature (22°C) for 48 h. Decreasing temperature of ASW to 15°C for depuration significantly increased the reductions of V. parahaemolyticus and V. vulnificus to 2.1 and 2.9 log MPN/g, respectively, after 48 h of process. However, depuration of oyster in ASW at 10 and 5°C were found less effective than at 15°C in reducing Vibrio in
the Gulf oysters. An extended depuration with ASW at 15°C for 96 h was capable of achieving 2.6 and 3.3 log MPN/g of reductions of V. parahaemolyticus and V. vulnificus, respectively, in the Gulf oysters. Study of effects of frozen storage at -10, -23 and -30°C on reducing V. parahaemolyticus in raw half-shell Pacific oyster (Crassostrea gigas) found that the population of the bacterium decreased faster in oysters stored at -10 than at -23 or -30°C. Holding half-shell Pacific oyster at -10°C for three months or at -23°C for four months was capable of achieving a greater than 3-log (MPN/g) reduction of V. parahaemolyticus in the Pacific oyster.Graduation date: 2008
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Shiu, Shu-Er. „Effect of high hydrostatic pressure (HHP) on the bacterial count and quality of shucked oysters“. Thesis, 1999. http://hdl.handle.net/1957/26558.
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The effects of various pressure treatments (OK, 30K, 60K, 75K psig) and
packing medium (water or cocktail sauce) on shucked oysters were investigated.
The pH, moisture content, microbiological tests (including aerobic plate count
(APC) and anaerobic plate count (ANPC)), enzyme assays (i.e. α-amylase, β-amylase,
lipase and peroxidase activities) were conducted to determine the quality
of pressure treated oysters during a 6 week shelf-life study. The moisture content
in water-packed oysters under OK, 30K, 60K and 75K psig pressure treatments was
slightly increased during storage, while that in cocktail sauce-packed samples was
significantly lower than in water-packed samples. Addition of cocktail sauce
lowered the pH in oysters, which effectively inhibited the microbial growth, but
altered the appearance. The microbial shelf-life of water-packed oysters with
pressure treatment of 60K and 75K psig was extended several weeks compared
with the controls while 30K psig had less of an effect. Pressure treatments did not
inhibit enzyme activities in oysters, however, the addition of cocktail sauce was
significant in inhibiting the enzyme activities in this study.Graduation date: 2000
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Grove, SF. „Development of a high pressure processing inactivation model for hepatitis A virus and its application in shellfish processing“. Thesis, 2008. https://eprints.utas.edu.au/19860/7/Grove_whole_thesis_ex_pub_mat.pdf.
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Hepatitis A virus (HAV) has been responsible for many large outbreaks of illness throughout the world, often resulting from consuming raw or minimally cooked filter-feeding shellfish contaminated with human faecal effluent.
High pressure processing (HPP) is an alternative food preservation technique to heat, preserving the flavour, appearance and nutritional value of high quality foods, including oysters, often with extended shelf life. In this study, the effectiveness of HPP in inactivating HAV was assessed.
HAV, suspended in buffered tissue culture media containing either 15 parts per thousand (ppt) or 30 ppt salt (NaCl), was treated with 300, 400 and 500 MPa for between 60 and 600 s. A log-linear function was developed in Microsoft\(^®\) Excel to model the kinetic inactivation data with the effects of NaCl, pressure and treatment time. The model can be used to predict HAV inactivation by interpolation at processing parameters not actually tested for in the laboratory.
For the model to be validated in oysters contaminated with HAV, methods for HAV extraction and purification from spiked oyster homogenate were first evaluated. Methods evaluated included the crude extraction method, modified from Kingsley and Richards (2003), and the PEG precipitation method, modified from the glycine-polyethylene glycol (PEG)-Tri reagent-poly(dT) extraction (GPTT) method described by Kingsley and Richards (2001). The PEG precipitation method achieved a mean recovery of 12.6%. With modification, including the use of antibiotic/antimycotic treatment prior to assay, the recovery was improved by up to 27.3%. In comparison, the crude extraction technique, which did not include a virion concentration step, recovered on average more than 40% of the initial spiked titre, and was chosen as a reliable method to extract HAV from oysters for cell culture quantitation.
Commercially grown and harvested Pacific oysters (Crassostrea gigas) were contaminated with HAV by natural accumulation, when immersed for up to 24 h in seawater contaminated with 1.1x10\(^7\) TCID\(^{50}\)/ml HAV. Infectious HAV was detected in only two of the six oysters tested, and less than 1% of the initial contaminating HAV titre was recovered in positive oysters, possibly due to the association of viruses and microalgae with oyster shells and aquarium surfaces throughout the trials.
A quantitative real-time reverse transcription PCR (qRT-PCR) method was developed as an alternative method for HAV detection in contaminated oysters to the infectivity assay. HAV was detected by qRT-PCR in all contaminated oysters, including those negative by infectivity assay. An immuno-magnetic bead separation technique was also developed, which additionally purified and concentrated virions, improving the sensitivity of detection by qRT-PCR.
The log-linear inactivation model was validated in homogenised oyster meat artificially inoculated with known titres of HAV. Salinity and temperature of samples were adjusted to that of buffered samples, while intermediate times and pressures were chosen for processing. The model tended to underpredict inactivation in homogenised oyster samples; i.e. it was fail-safe. Inactivation tended to be greater in spiked oyster homogenate compared to pure culture in treatments at higher pressures (400 — 500 MPa). The validated model may be a useful reference for Australian oyster processors wishing to implement HPP into their post-harvest processing regime.
Bücher zum Thema "Oyster contamination"
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Posadas, Benedict C. Consumer preferences for postharvest-processed raw oyster products in coastal Mississippi. Mississippi State, Miss.]: MAFES, Mississippi Agricultural & Forestry Experiment Station, 2011.
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Posadas, Benedict C. Consumer preferences for postharvest-processed raw oyster products in southern California. Mississippi State, Miss.]: MAFES, Mississippi Agricultural & Forestry Experiment Station, 2011.
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Cook, David W. Accumulation and fate of microorganisms in oysters: Paper presented at the Conference on Depuration Technology for the Louisiana Oyster Industry, Louisiana State University, Baton Rouge, Louisiana, May 6, 1986. [Ocean Springs, Miss.]: Mississippi-Alabama Sea Grant Consortium, 1986.
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Posadas, Benedict C. Consumer preferences for irradiated oysters. Mississippi State, Miss.]: MAFES, Mississippi Agricultural & Forestry Experiment Station, 2011.
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Environment, United States Congress House Committee on Merchant Marine and Fisheries Subcommittee on Fisheries and Wildlife Conservation and the. Shellfish contamination: Hearings before the Subcommittee on Fisheries and Wildlife Conservation and the Environment of the Committee on Merchant Marine and Fisheries, House of Representatives, One Hundredth Congress, second session, on shellfish diseases and H.R. 3969 ... shellfish contamination and shellfish bed closures, September 26, 1988. Washington: U.S. G.P.O., 1988.
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Kānponpūan khō̜ng Cryptosporidium sp. thī kō̜haikœ̄t rōk thō̜ngrūang nai hō̜i nāngrom bō̜riwēn chāifang thalē Phāk Tawanʻō̜k khō̜ng Prathēt Thai: Rāingān kānwičhai = Contamination of parasitic protozoa, Cryptosporidium sp. in oyster along the east coast of Thailand. [Chon Buri]: Sathāban Witthayāsāt thāng Thalē, Mahāwitthayālai Būraphā, 2008.
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Shiu, Shu-Er. Effect of high hydrostatic pressure (HHP) on the bacterial count and quality of shucked oysters. 1999.
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Kibria, Golam, Dayanthi Nugegoda und A. K. Yousuf Haroon. „Microplastic Pollution and Contamination of Seafood (Including Fish, Sharks, Mussels, Oysters, Shrimps and Seaweeds): A Global Overview“. In Emerging Contaminants and Associated Treatment Technologies, 277–322. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-89220-3_14.
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Alejandra Aguilar, Claudia, Yunuen Canedo, Carlos Montalvo, Alejandro Ruiz und Rocio Barreto. „Heavy Metal Contamination in a Protected Natural Area from Southeastern Mexico: Analysis of Risks to Human Health“. In Heavy Metals - Their Environmental Impacts and Mitigation [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95591.
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In this chapter, a little of the history of Carmen City, Mexico is addressed; this island is immersed in a Protected Natural Area and in the “Campeche Sound” an oil extraction site. Fishing natural resources were for many years the pillar of the development of the area; the most commercially important species are still shrimp, oysters and scales. Nowadays, although the volumes of capture have decreased considerably, different species of high commercial value are still extracted. The considerable development of the oil industry has brought with its economic development and a better quality of life for its inhabitants; however, the ravages of pollution, rapid population growth, and deforestation have been the unwanted factor. This chapter addresses the effects of heavy metals on human health through a risk analysis, based on the criteria of the US Environmental Protection Agency (USEPA) that was carried out for different commercial species based on carcinogenic factors and not carcinogenic; the results show that the risk from consumption of these species is “potentially dangerous” for human health, especially in those species that, due to their eating habits (mollusks, bivalves, clams) tend to bio-accumulate heavy metals, such as cadmium, which it has been considered by the International Agency for Research on Cancer (IARC) as a risk factor; for this reason, the importance of periodically evaluating and monitoring oyster extraction banks, clams and, in general, all fishery products. Mexican legislation and various international legislations dictate the maximum permissible and tolerable levels of heavy metals in fishery products; the organisms considered in this study exceeded the permissible limits in copper and nickel, which represents a risk for human consumption.
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„Contamination Proles and Temporal Trends of Persistent Organic Pollutants in Oysters from the Gulf of Mexico“. In Global Contamination Trends of Persistent Organic Chemicals, 449–86. CRC Press, 2011. http://dx.doi.org/10.1201/b11098-24.
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Kelly, Alan. „The Many Roles of Microorganisms“. In Molecules, Microbes, and Meals. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190687694.003.0010.
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As mentioned already several times, the world of living things can be divided quite simply into that which we can see (animals, plants, us!) and that which we cannot see. We share this planet with microscopic life that actually far outnumber the life-forms we can see and whose importance to our lives across a huge range of areas is completely out of proportion to their size. We need the assistance of microscopes or other tools to reveal the incredible diversity, richness, and sheer vastness of this hidden world. In terms of the sphere of human life with which we are concerned in this book, food, we worry about two things to do with microorganisms in food, which are safety and spoilage, but these are not the same thing. For example, milk containing a bacterium called Pseudomonas could look green, be stinky, and have lumps floating in it, but could be quite safe, while milk containing listeria could look fresh as could be but would make you very ill, perhaps even fatally, were you to drink it. In addition, yogurt containing bacteria called Bifidobacteria might not only be neither unpleasant nor dangerous but might actually be good for you, as these are probiotic bacteria, which are believed to colonize the human gut and help keep us healthy. So (cue Ennio Morricone music, and distinctive whistling), bacteria in food can be good (like the probiotics), bad (like the pathogens), or ugly (like the types that cause spoilage). Of course, the population of living things we cannot see in food is much broader than bacteria too and encompasses viruses (generally these don’t come in good or ugly variants, and are usually simply bad news, as when they cause food poisoning because of their contamination of products like oysters) and fungi such as yeasts and molds.
Konferenzberichte zum Thema "Oyster contamination"
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Rodrigues, Lisa J., Samantha R. Blemker, Sean Frangos und Steven T. Goldsmith. „METAL CONTAMINATION IN TWO OYSTER SPECIES FROM SOUTHWEST PUERTO RICO“. In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-303628.
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Al-Shamary, Noora. „Assessment of Organic and Inorganic Pollutants along the Qatari Coast“. In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2021. http://dx.doi.org/10.29117/quarfe.2021.0036.
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Qatar sits in the middle of the world’s most important hydrocarbon producing areas where significant regional refining activity and shipping traffic take place. In addition to significant local coastline, development prominently along the eastern coast, has taken place over recent decades. Protecting Qatar’s marine ecosystems from the adverse effects of environmental contaminants is a core component of the Environmental Development pillar within the National Vision 2030. However, a limited number of studies have investigated contaminant concentrations in the coastal environment of Qatar. The accumulation of contaminants in aquatic environments can affect coastal and marine ecosystems, and cause adverse effect on marine organisms and human health. This study aims to determine contamination in Qatar’s coastal environment by measuring organic and inorganic contaminants, along with physiochemical parameters, at four sites located on the contrasting east and west coast of the country. The Pearl Oyster Pinctada radiata, which is considered an iconic organism in Qatar, was used to determine a baseline of contaminants in an aquatic organism. Surface seawater, surface sediment and oysters were collected four times over two years in different seasons from the four sites. In-situ parameters (temperature, pH, and salinity), and abiotic parameters (TOC and grain sizes) were measured for seawater and sediment. Organic (TPHs, PAHs) and inorganic contaminants (trace metals including: Cd, Cu, Cr, Ni, Pb and Zn, T-Hg) were measured in all samples. Overall, Al Wakra (higher in boat traffic and fueling activities) on the east coast reported the highest levels of contaminants. High PAHs were observed in oyster tissues, while high Pb was noted in seawater and high Zn was observed in sediment and oyster. Benzo (a) pyrene was the highest compound detected in oyster. However, high TPHs were also noted in oyster tissues from Simaisma. At Al Khor, also on the east coast, high level of TPHs were recorded in seawater, while high PAHs and TOC observed in surface sediment, which had a relatively higher clay and silt content than other sites. Umm Bab (with a desalination plant near the coast), the sole sample site on the west coast, showed the highest level of TOC in seawater and sediment, highest Ni in seawater and highest total mercury in oyster. Our results, in general, report lower levels in seawater and sediment compared to other studies in the region and more widely; however, in oysters most of the contaminants are higher when compared to international guideline values. These higher levels indicate the potential for these filter-feeding organisms to absorb contaminants into their tissues from the environment that surrounds them. Additionally, bioaccumulation can occur. This study provides background information for further investigation to understand the presence and distribution of organic and inorganic contaminants in Qatar’s rapidly changing coastal environment. It indicates the usefulness of applying a holistic view to environmental monitoring including the use of biomonitoring.
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Frangos, Sean, und Lisa J. Rodrigues. „MORE THAN 15 YEARS OF CHANGE IN HEAVY METAL CONTAMINATION IN OYSTER AND CORAL TISSUE FROM KANEOHE BAY, HI“. In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-321046.
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