Purpose: In this study, a porcine skin model for bare-hand contact is compared to the fingers of human volunteers and cross-contamination of foods, food-contact surfaces and gloves with Salmonella and norovirus is quantified.
Methods: Human fingers (n = 10 volunteers) and sections of porcine skin (n = 5) were inoculated with ~ 5 log of either an avirulent strain of Salmonella enterica serovar Typhimurium (χ3985 Δcrp-11 Δcya-12) or Murine norovirus (MNV-1). After a 2-min dry time, fingers or skins were used to touch stainless steel surfaces, latex or nitrile gloves and leaves of sequentially-touched iceberg lettuce (n = 10). Bacteria and virus recovered from recipient surfaces were quantified by real time RT-qPCR (MNV-1) or standard bacterial culture on TSA and percent transfer rates were calculated.
Results: Transfer rates of Salmonella from human fingers or porcine skins to stainless steel were 17% and 38%, respectively. Salmonella transfer rates to thick latex, thin latex and nitrile gloves from human fingers (21%, 16% and 4%) were lower than the transfer rates from porcine skins (40%, 27% and 19%). Similar findings were observed for MNV-1 to latex glove surfaces, with transfer rates around 25% from human fingers but ranging from 31% – 52% from porcine skins. For each replicate, Salmonella was detected on the tenth lettuce leaf sequentially interfaced with contaminated porcine skins, but no Salmonella could be detected after the ninth leaf touched with human fingers. For both human fingers and porcine skins, MNV-1 was detected on all of the tenth sequentially-touched lettuce leaves.
Significance: In general, Salmonella and norovirus transfer to produce, food contact surfaces and gloves was overrepresented by porcine skins, making it a conservative model for pathogen cross-contamination after bare-hand contact.