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Factors controlling the survival of protozoan parasites. |
C. GERBA, Dept. of Microbiology & Immunology, Univ. of Arizona, Building 90, Tucson, AZ 85721 Several protozoan parasites are among the significant emerging foodborne pathogens. These include Giardia lamblia, Cryptosporidium parvum, and Cyclospora cayentanensis all of which are associated with diarrhea. All of these organisms produce an environmental resistant cyst or oocyst which aids their transmission by food and water. The organisms can survive for several months in surface and drinking water at ambient temperatures. The protozoa are sensitive to extreme temperatures (ie. heating and freezing) that destroy the cyst or oocyst. Oocysts can survive one minute at 60 C, but are inactivated at 67.5 C in 5 minutes. Oocysts are not inactivated in seven days at 10 C, but are inactivated in this same time period at -15 C. Exposure of oocysts to high hydrostatic pressures of 5.5 x 108 Pa will result in loss of infectivity. Oocyst viability is also affected by carbonation, pH, and alcohol content of foods.
Session 9, Survival of pathogenic microorganisms in hostile environments
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