Antibacterial blue light is a promising tool for inactivating Escherichia coli in the food sector due to its low risk of cross-stress tolerance

Background

Escherichia coli is an integral part of the colonic microflora, though its pathogenic intestinal strains can contaminate animal and plant products and cause significant challenges in the food industry. Thermal processing is one of the most common methods used to preserve food. Nevertheless, non-thermal antibacterial methods, such as antibacterial blue light (aBL), are attracting more interest due to the growing demand for minimally processed products. Thus, the current study was aimed at assessment whether the risk of co-selection for these two food processing approaches exist.

Results

The development of E. coli tolerance to both selective factors was observed after repeated exposure to sublethal doses of heat and aBL, and the observed adaptations were confirmed to be phenotypically stable. The results demonstrated that populations with increased tolerance to aBL also exhibited increased tolerance to temperature, while the sensitivity of temperature-tolerant populations to aBL did not change. We also identified 11 genes that could be involved in cross-stress tolerance. Neither adaptation changed the antibiotic sensitivity of the tolerant strains. Finally, short- and long-term pre-incubation at elevated temperatures significantly increased the tolerance of E. coli BW25113 to aBL.

Conclusions

The results obtained clearly demonstrate that aBL may serve as a complementary approach in food industry lacking resistance development and exerting no impact on microbial drug susceptibility. Nevertheless, the phenomenon of cross-tolerance should be considered an issue when designing food processing including sequential use of aBL and high temperature.

Graphical Abstract