Gulnihal Ozbay

Hemocytes Are Sites of Enteric Virus Persistence within Oysters

ABSTRACT The 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 na�ve (virus-free) oysters resulted in na�ve 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.

A Comparison of the Macrofaunal Communities Inhabiting a Crassostrea virginica Oyster Reef and Oyster Aquaculture Gear in Indian River Bay, Delaware

Abstract The eastern oyster (Crassostrea virginica) is a vital species in the estuaries of the mid-Atlantic United States. Whereas their filtering activity and biodeposition play an important role in the ecology of these systems, the reefs they form are one of the few sources of hard bottom habitat for fouling organisms and are the foundation of a rich biological community. This species has experienced drastic declines throughout the mid-Atlantic region in the last two centuries due to overfishing, habitat loss, and disease. Much interest and effort is now focused on restoring this important commercial and ecological resource. Whereas oyster reef restoration is central to the recovery of this species and the habitat it creates, oyster aquaculture can provide many of these same services albeit on a smaller scale. This is a two-part study, assessing the macrofaunal communities associated with subtidal modified rack and bag aquaculture, conducted over the summer and fall of 2006. The first part of this study compares the macro-epifaunal communities associated with two oyster habitats: a created oyster reef and oyster aquaculture cages. Both habitats were sampled with lift nets and compared using two-way ANOVAs between habitat and time. Secondly, we compared the sediment composition and macro-infaunal communities below the oyster cages with a nearby reference area of open sand/mud bottom. A significantly greater (P < 0.05) total abundance and species richness was found in the oyster cages, but significantly greater (P < 0.05) species evenness was found on the reef with species diversity similar between habitats. The sediments below the oyster cages showed a slight but significant (P < 0.05) reduction in its silt/clay fraction. The results of this study show that, this method of oyster aquaculture supports additional populations of ecologically and economically important macrofauna compared with a created oyster reef. Furthermore this study demonstrates that off-bottom oyster aquaculture operations in the mid-Atlantic United States are a beneficial addition to host estuaries and associated natural communities.

Oyster (Crassostrea virginica) gardening program for restoration in Delaware’s Inland Bays, USA

Eastern oyster, Crassostrea virginica is a keystone species in many estuarine bays. They clean the water by filtering out suspended particulates from the water column, while their reefs serve as valuable habitat for many ecologically and economically important macrofaunal species. However, with the ever-increasing development along our coastlines, the oyster population throughout the Mid-Atlantic region has plummeted as a result of overharvesting, extreme eutrophication, and disease. In response to this detrimental decline, many conservation organizations in the area have developed community-involvement programs commonly referred to as ‘oyster gardening’ to help restore the oyster population, while instilling within the community a strong sense of stewardship for their bays. Although the oyster gardening program in Delaware is relatively new, its popularity has grown tremendously. It is the hope of many Delaware residents that the reintegration of oysters into the Inland Bays will help to return their bays to the state of health in which they once were. Despite the expansion, further development of designated reef area is necessary to ensure the successful proliferation of C. virginica in Delaware’s Inland Bays.

Effects of High-Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters.

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

Floating oyster, Crassostrea virginica Gmelin 1791, aquaculture as habitat for fishes and macroinvertebrates in Delaware Inland Bays: the comparative value of oyster clusters and loose shell.

ABSTRACT The substantial decline of eastern oyster (Crassostrea virginica) stocks along the east coast of the United States has prompted the growth of many types of restoration and enhancement efforts. One of the most recent types is oyster gardening. Oysters grown in floating structures are subsequently planted in bays, where they continue to live, grow, and spawn; filter the water; contribute to the larval pool; and provide habitat. Our study is one of the first evaluations of habitat value provided by floating oyster gardens in a degraded mid-Atlantic estuary. Oyster growth and survival within the floats was monitored in a eutrophic, turbid, periodically hypoxic, soft-bottom coastal lagoon system. We examined the abundance and diversity of fishes and invertebrates with respect to 3 replicated treatments: live oyster clusters, disarticulated oyster shell, and a float with no shells or oysters. We also studied the effects of 2 cleaning frequencies (biweekly and monthly) on species assemblages, and the growth and survival of oysters, and monitored basic water quality parameters. The species assemblages in floats with oyster clusters were very similar to those with loose shell but considerably different than that of empty floats. Cleaning frequency (biweekly and monthly) did not affect the growth or survival of oysters. Location of floats within the canal system, however, was a large determinant of oyster vital rates as well as community structure. Forty-nine species of fishes and invertebrates, and 8 species of macroalgae were collected from floating oyster gardens, including 9 commercial or recreational fishery species, many of which are likely habitat limited in the Inland Bays because of the loss of tidal wetlands, oyster reefs, and seagrass beds. Newly settled juvenile oysters have been found for the first time within the floating oyster gear in the manmade, residential canal systems. Our results will be used to gauge the success of enhancement efforts and to improve our understanding of the effects oyster gardens on the Inland Bays ecosystem.

Antimicrobial activity of vinegar on bacterial species isolated from retail and local channel catfish (Ictalurus punctatus).

The use of vinegar was studied to reduce the growing number of illnesses caused by spoilage bacteria. The antimicrobial activity of organic vinegar was studied on various bacterial species isolated from domestic channel catfish fillets (Ictalurus punctatus). The effectiveness of the vinegar on the bacteria was measured. Bacteria isolated from catfish fillets with the largest inhibition zone were identified through 16S rDNA sequencing to better understand the spoilage bacteria that could be inhibited by vinegar to increase the quality of fishery products. Microbial changes of catfish fillets were evaluated following treatments of vinegar marinades during storage at 4°C and sensory evaluation was performed with baked catfish fillets to evaluate consumer sensory acceptability. Fish and chip vinegar was the most effective on Shewanella putrefaciens isolated from catfish fillets from the market and the pond. Microbial changes were evaluated and sensory evaluation was performed on different acetic acid dilutions of vinegar. Results showed that vinegar diluted to 0.5% acetic acid on catfish fillets would be suitable for prolonging shelf life and appealing to consumers. Vinegar as a natural antimicrobial product can improve the shelf life and safety of food products providing acceptable sensory quality at an affordable price and reducing economic lost due to spoiled catfish and other food products.

Oyster Hemocyte Mobilization and Increased Adhesion Activity After β-Glucan Administration

ABSTRACT In the Eastern oyster (Crassostrea virginica) hemocytes are important effector cells for maintenance of defense against pathogenic microorganisms. Various forms of &bgr;-glucans have been suggested for use in shrimp and fish aquaculture because of their potential to enhance disease resistance via hemocyte activation. To gain insight to the effects of these compounds in molluscs, changes in circulating oyster hemocyte numbers, population profiles, and adhesion were quantified after injection of &bgr;-1, 3-glucans. These agents included zymosan A or MacroGard, an immune stimulant suggested for aquaculture applications. Results were compared with those from estuarine water-injected control oysters at daily intervals for 3 days. MacroGard produced a rapid (by 1 day) elevation of total circulating hemocytes, which remained significant for 3 days; zymosan A stimulation of this response was not statistically significant. MacroGard administration resulted in a sustained increase in percent granulocytes in circulation. Zymosan A also produced an increment in the numbers of granulocytes that became significant by 3 days. Granulocytes are considered to be the most immunologically active hemocyte subclass. Both &bgr;-glucan preparations promoted hemocyte aggregation at days 1–3 after injection. Analysis of avidity of hemocyte aggregation using an index of clump cellular density confirmed this observation. Hemocytic aggregation is thought to be an indicator of cell activation. These results suggest that &bgr;-glucans can act to increase the numbers of circulating hemocytes available for defense responses, to promote longterm changes in the hemocyte profile favoring immunologically active cells, and to enhance hemocytic aggregation. Further studies of the physiological consequences of these effects of &bgr;-glucans on oyster hemocyte defense parameters are in progress.

Effects of High Hydrostatic Pressure on the Physical, Microbial, and Chemical Attributes of Oysters (Crassostrea virginica).

The change in the quality attributes (physical, microbial, and chemical) of oysters (Crassostrea virginica) after high hydrostatic pressure (HHP) treatment at 300 MPa at room temperature (RT, 25 °C) 300, 450, and 500 MPa at 0 °C for 2 min and control oysters without treatment were evaluated over 3 wk. The texture and tissue yield percentages of oysters HHP treated at 300 MPa, RT increased significantly (P < 0.05) compared to control. Aerobic and psychrotrophic bacteria in control oysters reached the spoilage point of 7 log CFU/g after 15 d. Coliform counts (log MPN/g) were low during storage with total and fecal coliforms less than 3.5 and 1.0. High pressure treated oysters at 500 MPa at 0 °C were significantly higher (P < 0.05) than oysters HHP treated at 300 MPa at 0 °C in lipid oxidation values. The highest pressure (500 MPa) treatment in this study, significantly (P < 0.05) decreased unsaturated fatty acid percentage compared to control. The glycogen content of control oysters at 3 wk was significantly higher (P < 0.05) when compared to HHP treated oysters [300 MPa, (RT); 450 MPa (0 °C); and 500 MPa (0 °C)]. HHP treatments of oysters were not significantly different in pH, percent salt extractable protein (SEP), and total lipid values compared to control. Based on our results, HHP prolongs the physical, microbial, and chemical quality of oysters.

Food waste in the United States: A contributing factor toward environmental instability

The world’s population continues to increase at record rates along with corresponding nutritional needs and related agricultural consequences. In the United States, food waste levels serve as dominant components of land-fill masses, oil and freshwater waste, methane and CO2 emissions, damage to wildlife ecosystems, and substantial financial losses. Agricultural effects on the environment were investigated through various research studies, referenced in this document, and efforts made toward food waste recycling were discussed as noteworthy models concerning improvements in sustainable agricultural practices. Food waste levels in the United States can be traced as faults of consumers, agricultural businesses, as well as federal legislation and there is an evident need for reform to maintain consumer health, viable foreign affairs, and environmental sustainability. Present agricultural practices are intense and rapid, increasing the risk of soil infertility and commercial alterations in production yields; repercussions well documented in neighboring nations. Experts argue that food waste in developed countries damages food availability around the world and, based on current agricultural practices and production, there is debate conc

Prevalence of Veterinary Drug Residues and Heavy Metals in Catfish Nuggets

Seafood such as catfish can sometimes become contaminated with chemicals and heavy metals at levels which would harm human health. There has been renewed interest by the USDA Food Safety Inspection Service (FSIS) in determining the incidence and prevalence of potentially harmful contaminants in catfish products. Many studies of retail catfish have focused on the fillet portion of the fish. Catfish nuggets are the fatty belly flap of the fish which is removed during processing and are sold as a separate product. Retail catfish nuggets from domestically raised catfish were collected in New Jersey, Pennsylvania, New York and Delaware and then tested for the presence of chemical contaminants including the heavy metals arsenic, lead, mercury, and cadmium. Of the 24 nugget samples tested none tested positive for the presence of arsenic or lead. Cadmium was detected in nine samples, but the levels were well below the regulatory action levels indicated for seafood. Mercury was detected in one catfish sample, but again the concentration was well below the U.S. FDA action limit for methyl mercury in fish. In addition, the presence of veterinary drug residues including malachite green, gentian violet and chloramphenicol in domestic catfish nuggets was also determined. One sample tested positive for the presence of gentian violet, however, given the low level detected (1.1 ppb) it is theorized to have occurred due to post-process contamination.