Survival of hepatitis A virus in spinach during low temperature storage.

Spinach leaves are frequently consumed raw and have been involved with past foodborne outbreaks. In this study, we examined the survival of hepatitis A virus (HAV) on fresh spinach leaves in moisture- and gas-permeable packages that were stored at 5.4 +/- 1.2 degrees C for up to 42 days. Different eluents including phosphate-buffered saline (PBS), pH 7.5 (with and without 2% serum), and 3% beef extract (pH 7.5 and 8) were compared for how efficiently they recovered viruses from spinach by using a simple elution procedure (<1 h). The recoveries were compared and determined by a plaque assay with FRhK-4 cells. Culture grade PBS containing 2% serum was found to be appropriate for HAV elution from spinach leaves, with an average recovery of 45% +/- 10%. Over 4 weeks of storage at 5.4 +/- 1.2 degrees C, HAV in spinach decreased slightly more than 1 log, with 6.75% of the original titer remaining. HAV survived under refrigerated temperatures on spinach leaves with a D-value of 28.6 days (equivalent to an inactivation rate of -0.035 log of HAV per day, r(2) = 0.88). In comparison, HAV in PBS containing 2% serum under the same storage conditions remained constant throughout 7 weeks. The inactivation rate of -0.035 log each day for HAV on spinach leaves was possibly due to the interaction of the virus and the leaf.