The development and elaboration of a risk-based sampling plan to control Listeria monocytogenes in a hospital food service operation

Introduction : Although listeriosis can occur in healthy adults and children, the most commonly affected populations include pregnant women, neonates, the elderly, and those persons who are immunosuppressed by medications or illness. The high prevalence of L. monocytogenes in foods in general, together with a high fatality rate of listeriosis suggests that L. monocytogenes represents an important hazard to human health. Purpose : The occurrence, spread, growth and survival of L. monocytogenes in foods and food environments has to be controlled. Therefore, a risk based sampling plan for the verification of the Food Safety Management System (FSMS) towards L. monocytogenes was developed and elaborated for a hospital Food Service Operation (FSO). Methods : First the classification of all used food types in various food categories, with similar microbiological ecology towards L. monocytogenes took place. Next a score system based on i) the reported epidemiological association of the food type with listeriosis outbreaks, ii) the reported prevalence of L. monocytogenes in the food types, and iii) the potential of L. monocytogenes to grow or survive during storage and/or further processing, was set up and through summation of the attributed scores, a minimum score of zero (low risk) and a maximum score of nine (high risk) could be obtained. A similar methodology was applied to identify critical sampling locations in the environment where L. monocytogenes is possibly present. Results : The attribution of risks to the defined food categories and critical sampling locations was the basis for selection of food types and environmental samples to be taken up in the sampling plan. Seven food products (n=49) and none of the environmental samples (n=145) were found to be positive for L. monocytogenes. Significance : The developed sampling plan can be used to improve the food safety output of the current FSMS, i.e. to control L. monocyogenes, in the FSO