FIG. 1.

Effect of pressure pretreatment on acid resistance of E. coli O157:H7 strain C9490. Cells were untreated (○) or treated in PBS for 10 min at 100 MPa (□), 200 MPa (▵), 300 MPa (▴), 400 MPa (■), or 500 MPa (●) before being diluted into TSBYE, pH₀ 3.5, and held at 37°C for up to 3 h. Data are means ± standard deviations (error bars). Arrows indicate that viable counts were below the limit of detection (100 CFU/ml).