Most of them don't have an answer to that question. Cooler contamination can also be avoided by washing cart wheels on a regular basis. At most plants, carts go through raw material areas, cooked areas and packaging areas. It's not difficult to place a sanitizing trough outside the cooler. At the very least, Austin says, plant personnel should regularly sanitize cart wheels by spraying sanitizer onto them.
Listeria tends to flourish in hidden places.
Listeria can become airborne. She recalls working with one plant that had to tear down refrigeration lines. Because the lines were not regularly cleaned, they became a shelter for the pathogen and a conduit carrying the bug into the air. Because the pathogen can become airborne, K.S.U.'s Phebus recommends periodically monitoring air quality. Even compressed air may be a source of pathogen growth, he says.