Various outbreaks of hepatitis A have been associated with the consumption of foods contaminated with hepatitis A virus (HAV). In this study, experiments were designed to develop rapid molecular methods to detect HAV in produce, to investigate its heat inactivation in dairy products and gamma irradiation resistance in produce, to assess its survival under modified atmosphere packaging (MAP) and to determine the amount of virus transferred from human hands to foods. The results demonstrated the following: (1) Immunomagnetic beads-PCR (IM-PCR), positively-charged 1MDS filters (F), or a combination of both (F-IM-PCR) methods were used to capture, concentrate and rapidly detect HAV in experimentally-contaminated lettuce and strawberries. Although the detection limit (10 PFU) of the F-IM-PCR was slightly less sensitive than that by the IM-PCR (0.5 PFU), the F-IM-PCR method has the potential to be of a greater sensitivity when detecting the virus in larger analytical units of foods (>50 mL) than the IM-PCR which is restricted to ≤20 mL, volumes. (2) Studies on the thermal resistance of HAV in three types of dairy products containing increased amounts of fat content (skim milk, homogenized milk; 3.5% MI7G, and table cream; 18% MFG) indicated that increased fat content seems to protect HAV and render it more heat-resistant as compared to those of lesser fat content. A list of time and temperature combinations required to achieve a 1 to 5 log 10 reduction in HAV titre is presented. (3) Exposure of HAV to gamma irradiation (60Co) doses ranging between 1 and 10 kGy showed that DIO values of 2.73 and 2.97 kGy were needed to achieve a 1-log10 reduction in HAV inoculated onto lettuce and strawberries, respectively. (4) Various MAP environments did not influence HAV survival on lettuce stored at 4°C. At room temperature, however, an atmosphere consisting of 70% CO2: 30% N2 slightly (p = 0.06) enhanced virus survival as compared to other storage conditions. (5) Approximately 10% of HAV inoculated onto the fingerpads of human volunteers was transferred to lettuce by touching. Treatment of the fingerpads with water, topical agents, or alcohol significantly (p < 0.05) reduced virus transfer from 10% down to ≤0.64%.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/8657 |
| Date | January 2000 |
| Creators | Bidawid, Sabah P. |
| Contributors | Sattar, Syed A., |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 186 p. |
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