Continuous transfer, growth kinetics, and disinfection recovery of Listeria monocytogenes in a simulated ready-to-eat meat factory environment.

The transfer of microorganisms between food and food-contact surfaces is a crucial pathway for their dissemination within the food chain and a significant cause of food contamination. The presence of Listeria monocytogenes biofilm residues in food processing environments can trigger persistent and recurrent food contamination, posing a serious challenge to the enforcement of food hygiene standards and the assurance of food safety. In this study, we used previously isolated L.monocytogenes strains from ready-to-eat meat factories as experimental strains, attempting to explore their continuous transfer, growth, and disinfection recovery patterns in the ready-to-eat meat factory environment. Our results indicate that after successive transfers, the residual rate of planktonic L.monocytogenes cells on stainless steel was lower than that of biofilm cells. The biofilms formed by ST5-WT strain following cold and acid treatments exhibited significantly higher fitting parameter p and detachment coefficient r during successive transfers than those formed by ST5-cured strain, which might indicate that plasmid-carrying strains have stronger transfer potential under these food processing stress conditions. In addition, growth experiments demonstrated that L.monocytogenes with an initial inoculum level of 2 Log CFU/g was unable to grow in ready-to-eat meat at -20 °C but remained viable for at least 10 weeks. At 4 °C, the lag period (λ) of L.monocytogenes ST5 was significantly lower than that of L.monocytogenes ST121 (p < 0.05). Furthermore, our disinfection experiments indicated that strict implementation of standardized disinfection treatment (500 mg/mL disinfectant + complete immersion for disinfection) can effectively reduce the number of biofilm cells. However, it is worth noting that L.monocytogenes may still recover in a suitable environment after disinfection. Overall, exploring the patterns of cross-transfer of persistent L.monocytogenes in food processing environments not only aids in accurately assessing its potential risks within the food processing chain but also provides a scientific basis for the prevention and eradication of L.monocytogenes.