No description available.

This study was designed to determine the survival of Vibrio parahaemolyticus in salted oysters as prepared in Korea. Three levels of salt concentration were included; 3.0%, 6.8%, and 10.6% of the weight of the raw oysters. Two methods were used to inoculate the products, surface-inoculation and injection into the oysters, which were then held at 18°C. Multiplication of V. parahaemolyticus (Japanese strain T-3765-1) did not occur in the salted oysters, except for a slight increase in numbers after 24 hours from surface-inoculated samples with 3.0% salt and all samples of injected oysters. The samples with the higher salt concentrations showed longer survival of the organisms. Numbers of survivors in surface-inoculated oysters were markedly reduced within three days; the samples of injected oysters did not show reduced numbers in this period. There were more survivors from the injected samples over the storage period than from the surface-inoculated samples. No viable cells were observed after seven days from the surface-inoculated samples with 3.0% salt and the injected samples with 3.0% salt, after eight days from the surface-inoculated samples with 6.8% salt, after nine days from the injected samples with 6.8% salt, and after 11 days from the injected samples with 10.6% salt. A small number of V. parahaemolyticus were recovered from the surface-inoculated samples with 10.6% salt after eight days, the last testing period for these samples. The results of pH measurement suggested that the samples with higher salt concentration may have prolonged survival of V. parahaemolyticus through the effect of the higher pH value. An analysis of variance revealed a significant difference (5% level) in recovery between a modified isolation medium (Twedt and Novelli) and thiosulfate-citrate-bile salts-sucrose agar. Salt concentrations of 3.0%, 6.8%, and 10.6% slightly reduced the total bacterial counts after three days from the two lots of oysters used for the surfaceinoculated samples and further reduction was observed after seven days; reduction in numbers was not detected within 8 or 11 days from the two lots used for the injected samples. The latter two lots had much lower plate counts at the beginning of the experiment. No relationship was found between pH and total bacterial counts on the salted oysters. / Graduation date: 1973

No description available.

Thesis (Ph. D.)--Johns Hopkins University. / Biographical sketch. "Quart. journ. micr. sci. vol. 49, n. s." "Literature": p. 683-685.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 78-97). Also available on the World Wide Web.

Aflatoxins B₁, B₂, G₁ and G₂ and a crude preparation of freshly prepared aflatoxin produced by Aspergillus parasiticus NRRL 2999 were added to the fertilized oyster, Crassostrea gigas, eggs. The addition of 2, 3, 4 and 5 ug/ml of aflatoxin B₁, inhibited the first cell division of fertilized oyster eggs by 10, 30, 70 and 90 percent, respectively. First cell division did not appear to be inhibited by 5 ug/ml of either aflatoxins B₂,G₁ or G₂ A change in the fine structure of the fertilized oyster eggs was observed following the addition of 5 ug/ml of aflatoxin B₁. Visible changes or alterations in the aflatoxin treated zygotes were not readily detectible in the electron micrographs except for the segregation of the fibrillar and granular components of the nucleolus, an apparent decrease of the vesicles surrounding the cisternal rough endoplasmic reticulum, and the final inhibition of the mitotic division process before first cell division. The data is consistant with the observed cytotoxic effects suggesting an inhibition at the cell DNA replication, RNA transcription and protein translational levels in the aflatoxin B₁ treated oyster zygotes. / Land and Food Systems, Faculty of / Graduate

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

A direct enrichment procedure has been developed for selectively recovering low numbers of Campylobacter jejuni and Campylobacter coli from oyster tissue. This procedure makes use of a selective enrichment step, using a broth medium composed of 2% proteose peptone, 1% yeast extract, 0.2% potassium L-aspartate, 0.25% sodium chloride as basal medium (PYA broth)plus 0.2% bacteriological charcoal, polymyxin (5000 IU/ litre), cefoperazone(30 mg/litre), trimethoprim (10 mg/litre), cycloheximide (50 mg/litre), sodium pyruvate (0.25g/litre), sodium metabisulphate (0.25g/litre) and ferrous sulphate (0.25g/litre). In this study the procedure has been used to study the occurrence of thermophilic campylobacters in Sydney rock oysters. Seventy nine samples were screened during the winter months of April to July in 1985. Approximately 8% of the samples contained C.jejuni and 6% of the samples were positive for C.coli. The survival of C.jejuni and C.coli in the Sydney rock oyster was also investigated and results discussed. In contaminated shell stock stored at 20 and 30 degrees Centigrade, C.jejuni and C.coli survived for periods varying from 2 to 9 days. The failure of the organism to multiply in oyster tissue at any of these temperatures studied is an important phenomenon. / Master of Science (Hons)

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 65-73)

Thesis (doctoral)--Université de Rennes I, 2003. / Includes bibliographical references (p. 249-261). Also available on the Internet.