Sublethal sanitizer stress and adaptive response of Escherichia coli O157:H7

The effect of sublethal exposure to peroxyacetic acid (PAA) sanitizer on adaptation to peroxidative stress and development of thermal cross-resistance was investigated in Escherichia coli O157:H7. Acute sublethal PAA sanitizer exposure was used to represent a contact scenario. Cultures were grown in Trypticase soy-yeast extract broth. Acute treatment cultures were pretreated with 0.1% PAA, then all cultures were challenged at either 80 mM H₂O₂ or 54°C. Acute and peroxide control cultures showed substantially increased peroxidative tolerance (D_80mM > 2 h) versus negative control cultures not exposed to sanitizer (D_80mM = 0.19 ± 0.03 h). The inactivation rate of the acetic acid control (D_80mM = 0.21 ± 0.05 h) was similar to the negative control rate. Acute (D_54°C = 0.55 ± 0.07 h) cultures did not exhibit increased thermal resistance versus the control (D_54°C = 0.54 ± 0.07 h). Thermal injury was determined as difference in D_54°C value (ΔD_54°C) obtained on pyruvate and deoxycholate media. Thermal-induced injury was not observed in either control (ΔD_54°C = 0.04 h) or acute (ΔD_54°C = 0.05 h) cultures.