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.
Penicillic acid and ochratoxin A are environmentally important toxic fungal metabolites (mycotoxins) that are synergistic in combination. The effects of penicillic acid on the pancreatic enzyme, carboxypeptidase A were investigated in vitro and in vivo. A broad range of inhibition in vitro of the enzyme by PA was demonstrated with a half-maximal inhibitory concentration equal to 1.1 x 10(-4) M PA. Inhibition of carboxypeptidase A was time and temperature dependent, and resulted in decreased conversion of parent ochratoxin A to the non-toxic metabolite, ochratoxin alpha. Studies in vivo demonstrated a penicillic acid-dependent inhibition of pancreatic carboxypeptidase A activity in the mouse and the chicken following multiple oral exposure. It is postulated that the mode of toxic interaction of the two mycotoxins may be due, in part, to impaired detoxification of ochratoxin A through penicillic acid depletion of carboxypeptidase A activity.
Vibrio vulnificus hemolysin, purified by quantitative isoelectric focusing, was used to prepare rabbit and goat anti-hemolysin. The resulting antibodies were used as capture and detector antibody reagents in a sandwich enzyme-linked immunosorbent assay (ELISA) to detect V. vulnificus in environmental samples. By this technique, 4 laboratory-maintained V. vulnificus strains and 33 environmental V. vulnificus isolates were detected. Also, the technique distinguished five other Vibrio species from V. vulnificus, and when it was used in combination with colistin-polymyxin-cellobiose agar, 31 non-V. vulnificus isolates were excluded. This sandwich ELISA compared favorably with the current Food and Drug Administration standard immunoassay in confirming presumptive V. vulnificus colonies from environmental specimens: oysters, sediment, and seawater. Among 340 presumptive V. vulnificus colonies, the sandwich ELISA detected 95% of the confirmed V. vulnificus colonies. Equally important, the technique correctly distinguished 99% of the non-V. vulnificus colonies. The sandwich ELISA offers time-saving and labor-saving advantages over the currently accepted immunoassay.
The critical infrastructure sectors of agriculture and food systems face increasing threats of bioterrorism from agents associated with emerging infectious diseases. These disease agents include human‐specific pathogens, zoonotic pathogens, foreign animal diseases, and plant pathogens. For the purpose of strengthening defenses through awareness and preparation, this article considers the risk factors of availability and cost, ease and route of dissemination, virulence and susceptible host range, and impact and public perception. The threat risks from glanders and melioidosis are presented in more detail.
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