355-3 Role of Salinity and Different Bacterial Phyla On the Survival of Escherichia Coli O157:H7 In Leafy Green Producing Soils.



Wednesday, October 19, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Abasiofiok Ibekwe and JINCAI Ma, USDA-ARS, Riverside, CA
E. coli O157:H7 has been implicated in many foodborne illnesses caused by the consumption of contaminated fresh produce. However, data on persistence of E. coli O157:H7 in major fresh produce growing soils are limited. In this study, survival of E. coli O157:H7 in 32 soil (16 organic, 16 conventional) from California and Arizona were investigated. The survival time (time needed to reach detection limit, 100 CFU g-1) of E. coli O157:H7 in soils were correlated with soil properties, and bacterial community structure using 454 pyrosequencing. Results showed that the best survival of E. coli O157:H7 was observed in the soils from northern CA, and in organic soils from Arizona. Principal component analysis and stepwise regression analysis showed that overall survival of E. coli O157:H7 in soils were strongly affected by salinity (EC), water soluble organic carbon (WSOC), and total nitrogen (T-N) in soil water extract (soil:water, 1:1) with EC being the dominant factor. Linear regression analysis showed that the survival of E. coli O157:H7 in all soils was closely correlated with the EC, and the survival time decreased with increasing EC in salts amended soils. Linear regression analysis confirmed  that the concentrations of Na+ in soil water extracts were highly related to the survival of E. coli O157:H7 (P < 0.05) especially in conventional soils. Survival of E. coli O157:H7 was significantly enhanced with the abundance of Actinobacteria (P < 0.05) as determined by the 454-pyrosequencing analysis.
See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Advanced Techniques for Assessing and Interpreting Microbial Community Function: II