Heterogeneity of growth and toxigenicity of Shiga toxin- producing Escherichia coli under different stress conditions

Abstract:

[Objective] This paper aims to explore the growth and toxigenicity of Shiga toxin-producing Escherichia coli (STEC) under different stress conditions, and to provide basic data reference for the study of the stress response mechanism of STEC strains under stress. [Methods] Three STEC strains were selected for adaptive subculture at different pH values, different salt concentrations, and different temperatures, and their growth heterogeneity under stress was analyzed via the Gompertz model. The toxigenicity of the strains under stress was analyzed by the Vero cytotoxicity assay. [Results] Except the ST462 strain at pH 5.0, other STEC strains showed decrease in the maximum specific growth rate (μ_max) and extension of the lag period (λ) under stress conditions (pH 5.0 or 9.0, 1.5% NaCl or 2.5% NaCl, 10 ℃) (P<0.01). The viability of the cells treated with the toxins extracted from STEC strains under different stress conditions was lower than that under the optimal control conditions, while the opposite trend was observed at pH 5.0. [Conclusion] STEC strains activated the stress response mechanism under alkaline stress, higher salt concentrations, and low temperatures. Although the growth was inhibited, the toxins produced by the strains exposed to stress aggravated the damage to Vero cells, demonstrating increased toxicity. By analyzing the heterogeneity of the growth and toxigenicity in a stressful environment, this study helps to comprehensively understand the biological characteristics of STEC strains under stress and has guiding significance for improving the detection, sterilization, and prevention measures during food processing to ensure food safety.