Heat Processing of Oysters Naturally Contaminated with Vibrio cholerae Serotype 01.

Pathogenic Vibrio cholerae 0-Group 1 survived for more than 3 weeks in artificial sea water with little loss in viability. Live oysters placed in such contaminated, artificial sea water took up but did not concentrate V. cholerae . Heat treatments provided by an in-can pasteurization process and by preparation of naturally contaminated oysters according to common recipes effectively reduced the numbers of V. cholerae by 5 logs/g.

Evaluation of the Enteropathogenicity of Klebsiella pneumoniae Isolates from Summer-Harvested Louisiana Oysters.

Klebsiella pneumoniae isolates were recovered in increased numbers from oysters harvested during the warm months of the year from approved and classified waters. A total of 76 oyster isolates was examined using in vivo and in vitro assays. The nonpathogenic responses of the strains studied suggest that environmental strains are not a public health risk.

Trimming as a means of removing patulin from fungus-rotted apples.

Penicillium expansum 1071, 1172, NRLL 973, and Penicillium patulum ATCC 24550 were inoculated into Red Delicious, Golden Delicious, and McIntosh apples. The decayed tissue was trimmed from the sound tissue, each fraction was weighed, and the patulin concentration in the juice was assayed by thin layer chromatography. The quantity of patulin in the whole apples and in decayed tissues was calculated and these values were used to determine the percentage of total patulin removed by trimming. The patulin content ranged from 140 to 4880 mug/apple. Trimming removed 93-99% of the total patulin, regardless of incubation temperature, fungus strain, or apple variety. Trimming of defective tissue from fungus-rotted apples could substantially reduce the patulin concentration.

Effects of purified altertoxins I, II, and III in the metabolic communication V79 system.

Purified Alternaria alternata altertoxins I, II, and III were evaluated for comparative cytotoxicity and ability to inhibit gap junction communication in the Chinese hamster lung metabolic cooperation assay. The noncytotoxic test range for each altertoxin was determined for the metabolic communication assays: altertoxin I, 1, 2, 3, 4, 5 micrograms/ml; altertoxin II, 0.02, 0.008, 0.006, 0.004, 0.002, 0.0008 micrograms/ml; and altertoxin III, 0.2, 0.1, 0.08, 0.06, 0.04 micrograms/ml. Altertoxin II was the most cytoxic in the V79 system, followed by altertoxins III and I. The last cytotoxic of the three, altertoxin I, weakly disrupted metabolic communication at two concentrations (4 and 5 micrograms/ml). Altertoxins III and II did not significantly inhibit gap junction communication more than the weak tumor promoter 4-O-methyl ether tetradecanoylphorbol 13-acetate.

Adherence and Hemagglutination of Mammalian Cells by Epidemiologically Distinct Strains of Vibrio vulnificus.

Thirty-eight strains of Vibrio vulnificus were examined for their ability to adhere to human buccal epithelial cells and to hemagglutinate mammalian erythrocytes. Clinical isolates showed significantly greater mean adherence than environmental strains. The ability to hemagglutinate human erythrocytes was closely associated with vigorous buccal cell adherence.

Effect of Temperature and Suspending Vehicle on Survival of Vibrio parahaemolyticus and Vibrio vulnificus.

Four strains of Vibrio vulnificus and two strains of Vibrio parahaemolyticus from clinical and environmental sources were examined for their ability to survive storage at 4 and -20°C in shrimp homogenate and at -80°C in shrimp homogenate, fetal bovine serum and dimethyl sulfoxide. Cell counts declined with time at 4 and -20°C but they remained stable after freezing at -80°C. Dimethyl sulfoxide was the superior menstruum at -80°C because it protected against freezing lethality.

Demonstration of invasiveness of Vibrio parahaemolyticus in adult rabbits by immunofluorescence.

To determine possible pathogenesis of Vibrio parahaemolyticus-host-organ system interactions, studies of invasiveness were made by a direct fluorescent-antibody method. Broth cultures of live cells isolated from seafish or symptomatic humans were inoculated separately into ligated ileal loops of young New Zealand white rabbits. After suitable incubation, rabbits were sacrificed, and ileal loops and tissue specimens were aseptically removed. Ileal loops were prepared and stained with specific fluorescein-tagged antibody, and organ specimens were cultured for isolation of the inoculated Vibrio strain. All strains tested penetrated into the lamina propria of the ileum and were isolated from the cultured tissue specimens, indicating that the organism is capable of more than a superficial colonization of the gut. The presence of Vibrio in cultured tissue specimens suggests invasion of deeper tissue by either the lymphatic or the circulatory system.

Detection of heat-labile-enterotoxin-producing colonies of Escherichia coli and Vibrio cholerae by solid-phase sandwich radioimmunoassays.

A solid-phase sandwich assay that was able to differentiate heat-labile-enterotoxin-producing colonies of Escherichia coli and choleratoxin-producing colonies of Vibrio cholerae from nontoxigenic colonies is described. Flexible polyvinyl chloride plastic film coated with antibody molecules was allowed to react with partially lysed bacterial colonies in a standard petri dish. The immobilized antigen on the plastic film was then labeled with radioiodinated antibody. Autoradiography identified antigen-containing colonies. As little as 5 to 25 pg of pure toxin contained in a 3- to 4-mm-diameter circle was reliably detected by this method. The synthesis of heat-labile enterotoxin and choleratoxin by cells growing on selective media such as eosin methylene blue agar, MacConkey agar, Endo agar, and thiosulfate-citrate-bile salts-sucrose agar was demonstrated. The method appears to be suitable for large-scale surveys.

Foodborne enterotoxigenic Escherichia coli: detection and enumeration by DNA colony hybridization.

Four methods were compared for detecting heat-labile toxin production by Escherichia coli: DNA colony hybridization, two enzyme-linked immunosorbent assays, and the mouse Y-1 adrenal cell reaction. Although results of the methods were in general agreement, there were some differences in specificity and sensitivity. DNA colony hybridization was used to detect and enumerate enterotoxigenic E. coli isolates in artificially contaminated food without enrichment. Sensitivity level was 100 cells per g.