Computational modeling and experimental data collection for Salmonella Enteritidis PT 30 cross-contamination and dry...

A major cause of Salmonella spp. foodborne outbreaks in milk powder is cross-contamination in production environments. Transfer experiments under different conditions were performed between different donors and acceptors (stainless steel coupon, paper towel, and milk powder). A Monte Carlo simulation was developed to model the cross-contamination of Salmonella Enteritidis PT 30 (S. PT 30) and dry cleaning interventions in milk powder production environments under 8 scenarios. Inputs to the model included the initial level of S. PT 30, the proportion of milk powder in contact with the surface, the normal force for dry wiping, the log transfer coefficient (log TC) under various conditions, and the reduction proportion on the surface with inoculated milk powder residues after dry cleaning. The model's outputs mainly included the quantity and the concentration (log CFU/g) of contaminated milk powder. Initial level, normal force, inoculation method, and transfer direction significantly affected the log TC (p < 0.05). After a contamination breach on the contact surface in scenario 1, milk powder was contaminated. Milk powder could still be contaminated with a low concentration even after multiple S. PT 30 transfer steps from different contamination sources to the contact surface in scenarios 2-5. Dry wiping effectively reduced the quantity and the concentration of contaminated milk powder in scenarios 6-7. But multiple dry wipes were needed to remove all S. PT 30 from the surface in scenario 8. The developed model can be used to evaluate the risk of cross-contamination in various scenarios in milk powder production environments and provide guidance for hygiene intervention strategies.