Development of heat tolerance resulted from adaptation of Salmonella Enteritidis to sublethal concentration of sodium hypochlorite

Sodium hypochlorite (NaClO) is a widely used disinfectant in food processing environments. However, its improper use can lead Salmonella to develop tolerance to other stresses, which threatens food safety and human health. In this study, the survival ability assays showed that adaptation of S. Enteritidis to NaClO resulted in the development of heat tolerance at 55 °C and 63 °C. NaClO-adapted S. Enteritidis also showed a survival benefit in milk at 55 °C and 63 °C. NaClO-adapted S. Enteritidis exhibited a decrease in accumulation of reactive oxygen species (ROS) compared to non-adapted S. Enteritidis after exposure to 63 °C. Moreover, compared to non-adapted S. Enteritidis, the membrane fatty acids C16:0 and cyclo-heptadecanoic acid Cyc17 were significantly increased in NaClO-adapted S. Enteritidis, whereas UFA to SFA ratio was observed to decrease from 0.52 ± 0.04 to 0.41 ± 0.04. These changes resulted in a decrease in membrane fluidity of NaClO-adapted S. Enteritidis. Furthermore, RT-qPCR analysis revealed a considerable increase in the expression levels of heat shock-related genes in NaClO-adapted S . Enteritidis with or without heat treatment, in comparison to non-adapted S . Enteritidis. It was noteworthy that upregulation was 7.30-fold for dnaK , 11.62-fold for ibpA , and 3.92-fold for rpoH under heat treatment, suggesting that these genes played important roles in the development of heat tolerance. Taken together, adaptation of S . Enteritidis to NaClO resulted in the development of heat tolerance, which might increase the risk of cross-contamination and salmonellosis in the food industry.