Microwave Inactivation of Cyclospora cayetanensis Sporulation and Viability of Cryptosporidium parvum Oocysts

Abstract

The efficacy of microwave heating on the viability of Cryptosporidium parvum oocysts and on the sporulation of Cyclospora cayetanensis oocysts for various periods of cooking times (0, 10, 15, 20, 30, and 45 s) at 100% power was determined. Cyclospora oocysts were stored in 2.5% dichromate at 23 degrees C for 2 weeks, and sporulation rates were then determined. The 4',6-diamidino-2-phenylindole and propidium iodide vital stain and the neonate animal infectivity assay determined Cryptosporidium oocyst viability. Cryptosporidium oocysts could be completely inactivated with as little as 20 s of cooking time, whereas Cyclospora sporulation was observed up to 45 s. Two of the examined microwave ovens were more effective at reducing sporulation and viability than the third one. Because of the variability of temperature achieved by the various ovens, cooking time was not an accurate parameter for parasite inactivation. Cryptosporidium oocysts could be inactivated only when temperatures of 80 degrees C or higher were reached in the microwave ovens.

Effect of Chlorine, Blanching, Freezing, and Microwave Heating on Cryptosporidium parvum Viability Inoculated on Green Peppers

“…Cryptosporidium's resistance to chlorine has also been reported in other studies (8,15). Furthermore, because Cryptosporidium oocysts have been shown to be internalized through the stomata and because they resist hours of washing, the risk of not eliminating Cryptosporidium oocysts from contaminated vegetables by chlorinated washing bath is even greater (16,19). These findings have implications for the safety of minimally processed and ready-to-eat vegetables as these products are assumed to be safe and free of pathogens by the consumers who do not further wash the products before consumption.…”

“…Furthermore, fresh or frozen vegetables are often cooked at home, using microwave ovens, and many convenience vegetable products are now available at retail in microwaveable packaging. Athome microwave cooking of vegetables could therefore also affect the viability of microorganisms (19).…”

Update on Cyclospora cayetanensis , a Food-Borne and Waterborne Parasite

“…Sporulation at 50°C was minimal (0.01 to 0.03%). Microwave heating inactivates Cyclospora oocysts in water when the temperature reaches 80°C or higher (139). These temperatures can be reached in shorter periods than those with conventional heating.…”

“…Microwave heating of Cyclospora oocysts can inactivate oocysts; however, more time is required to kill Cyclospora oocysts than to kill Cryptosporidium oocysts. Short exposures to a high temperature (96°C for 45 s) did not completely prevent the sporulation of Cyclospora (139). Chemicals have been tested for the ability to interfere with the sporulation of Cyclospora.…”

Cyclosporiasis: An update

“…Extremes of temperature seem to be inhibitory in both food substrates, whereas no effect was noted when incubation occurred at 4°C and 23°C for up to 1 week. In another study, Cyclospora sporulation was observed even with microwave exposure at 100% power for 45 seconds [35]. Various fungicides and insecticides also have been shown to not affect sporulation [36].…”