Effect of soil composition, temperature, indigenous microflora, and environmental conditions on the survival of Escherichia coli O157:H7.

The survival of Escherichia coli O157:H7 in replicate soil microcosms was quantified in 2 types of silty clay loam soil (high carbon and low carbon) under either sterile or nonsterile conditions. Microcosms were held at -21, 4, and 22 degrees C under constant soil moisture content. Differences existed (P < 0.05) in survival of E. coli O157:H7 in low- and high-carbon soil at all temperatures, indicating an important role of soil composition on the survival of this pathogen. The highest death rate of E. coli O157:H7 in sterile soil occurred in the low-carbon soil at 4 degrees C, whereas in nonsterile soil the highest death rate was observed in the low-carbon soil at 22 degrees C. These results suggest that the most lethal effects on E. coli O157:H7 in the sterile system occurred via the synergy of nutrient limitation and cold stress, whereas in the nonsterile system lethality was owing to inhibition by indigenous soil microorganisms and starvation. Results obtained from an in situ field survival experiment demonstrated the apparent sensitivity of E. coli O157:H7 cells to dehydration, information that may be used to reduce environmental spread of this pathogen as well as formulate appropriate waste management strategies.