HOSPITAL GREEN SALADS AND THE EFFECTS OF WASHING THEM

Each week from April 1989 to February 1990, a plate of green salad prepared in the hospital kitchen was examined microbiologically. Of the 256 plates examined, 51% had total viable counts (TVCs) of ≥ 105 colony forming units (cfu) g-1. Staphylococcus aureus was present in 13 samples and Escherichia coli in one sample. No Listeria monocytogenes, Clostridium perfringens or Salmonella spp. were isolated. The effect of washing mustard and cress, cucumber and the different layers of lettuce leaves was examined. Washing the salad by agitating it under running tap water in a colander for 2 min reduced the total bacterial counts by 10-fold. The inner leaves of a lettuce had TVCs < 104cfu g-1, at least 10-100-fold less than the outer leaves. Cucumber after washing had similar TVCs as after peeling. Five of six samples of mustard and cress had TVCs of at least 106cfu g-1 before washing. As a consequence, mustard and cress was no longer used in our salads. © 1991.