Ozone inactivation of norovirus surrogates on fresh produce.

Preharvest contamination of produce by foodborne viruses can occur through a variety of agents, including animal feces/manures, soil, irrigation water, animals, and human handling. Problems of contamination are magnified by potential countrywide distribution. Postharvest processing of produce can involve spraying, washing, or immersion into water with disinfectants; however, disinfectants, including chlorine, have varying effects on viruses and harmful by-products pose a concern. The use of ozone as a disinfectant in produce washes has shown great promise for bacterial pathogens, but limited research exists on its efficacy on viruses. This study compares ozone inactivation of human norovirus surrogates (feline calicivirus [FCV] and murine norovirus [MNV]) on produce (green onions and lettuce) and in sterile water. Green onions and lettuce inoculated with FCV or MNV were treated with ozone (6.25 ppm) for 0.5- to 10-min time intervals. Infectivity was determined by 50% tissue culture infectious dose (TCID(50)) and plaque assay for FCV and MNV, respectively. After 5 min of ozone treatment, >6 log TCID(50)/ml of FCV was inactivated in water and ∼2-log TCID(50)/ml on lettuce and green onions. MNV inoculated onto green onions and lettuce showed a >2-log reduction after 1 min of ozone treatment. The food matrix played the largest role in protection against ozone inactivation. These results indicate that ozone is an alternative method to reduce viral contamination on the surface of fresh produce.

Detection of Cryptosporidium parvum oocysts on fresh vegetables and 1 herbs using antibodies specific for a Cryptosporidium parvum viral antigen.

The purpose of this study was to determine if the viral symbiont of Cryptosporidium parvum (CPV) sporozoites could be used as a target for sensitive detection of the parasite in food samples. Polyclonal sera specific to the recombinant viral capsid protein (rCPV40) was used in a dot blot hybridization assay to detect oocysts recovered from green onions and cilantro. Small batches of chopped green onions and cilantro leaves were artificially contaminated with three different concentrations of oocysts: 10(6), 10(2), and 10(1). rCPV40 was superior in detecting oocysts compared with other antibodies directed toward total oocyst protein and oocyst surface antigens. This study provides evidence that CPV is an excellent target for sensitive detection of C. parvum oocysts in foods.