Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: testing the five-second rule

ABSTRACT

Aims: Three experiments were conducted to determine the survival and transfer of Salmonella Typhimurium from wood, tile or carpet to bologna (sausage) and bread.

Methods and Results:  Experiment 1. After 28 days, 1·5 to 2·5 log₁₀ CFU cm⁻² remained on tile from and the more concentrated media facilitated the survival of S. Typhimurium compared with the more dilute solutions.

Experiments 2 and 3. The bacterial transfer rate to food decreased as the bacterial residence time on the surface increased from 2, 4, 8 to 24 h with transfers of 6·5, 4·8, 4·6 and 3·9 log CFU ml⁻¹ in the rinse solutions, respectively. Over 99% of bacterial cells were transferred from the tile to the bologna after 5 s of bologna exposure to tile. Transfer from carpet to bologna was very low (<0·5%) when compared with the transfer from wood and tile (5–68%).

Conclusions: (i) Salmonella Typhimurium can survive for up to 4 weeks on dry surfaces in high-enough populations to be transferred to foods and (ii) S. Typhimurium can be transferred to the foods tested almost immediately on contact.

Significance and Impact of the Study: This study demonstrated the ability of bacteria to survive and cross-contaminate other foods even after long periods of time on dry surfaces, thus reinforcing the importance of sanitation on food contact to minimize the risk of foodborne illness.