Examination of factors for use as potential predictors of human enteric pathogen survival in soil
Article first published online: 13 NOV 2013
© 2013 The Society for Applied Microbiology
Journal of Applied Microbiology
Volume 116, Issue 2, pages 335–349, February 2014
How to Cite
Erickson, M.C., Habteselassie, M.Y., Liao, J., Webb, C.C., Mantripragada, V., Davey, L.E. and Doyle, M.P. (2014), Examination of factors for use as potential predictors of human enteric pathogen survival in soil. Journal of Applied Microbiology, 116: 335–349. doi: 10.1111/jam.12373
- Issue published online: 17 JAN 2014
- Article first published online: 13 NOV 2013
- Accepted manuscript online: 25 OCT 2013 03:14AM EST
- Manuscript Accepted: 21 OCT 2013
- Manuscript Revised: 4 OCT 2013
- Manuscript Received: 10 JUL 2013
- USDA NIFSI. Grant Number: # 2007-51110-03812
- E. coli O157:H7;
- microbial diversity;
- Salmonella ;
Three soils that varied in their physicochemical characteristics and microbial diversity were inoculated with Escherichia coli O157:H7 and Salmonella to determine the relative impact of abiotic and biotic factors on the pathogens' survival when the soil was held at 25°C.
Methods and Results
Three soils that were classified as having low, medium and high microbial diversity were divided into two batches for adjustment to 20% of water-holding capacity and to 40% of water-holding capacity. Soils were inoculated with both green fluorescent-labelled E. coli O157:H7 and red fluorescent-labelled Salmonella (5 log CFU g−1 dry weight) and held at 25°C. Pathogens inoculated into an acidic soil died off within 9 weeks, whereas they were still detected in the other two soils by enrichment culture after 18 weeks. Moisture did not affect inactivation of E. coli O157:H7, but did affect Salmonella inactivation in soil having the greatest organic load and microbial diversity. Using multiple linear regression analysis, 98·7% of the variability in the inactivation rate for E. coli O157:H7 was explained by a model that included the variables of initial pH and electrical conductivity. Salmonella's inactivation rate was predicted by a model that included pH and initial cell numbers of copiotrophic and oligotrophic bacteria.
This study provided evidence of specific properties that impact inactivation of E. coli O157:H7 and Salmonella in soils at 25°C.
Significance and Impact of the Study
Identification of factors influential in the die-off of enteric pathogens will assist in developing guidelines for safe intervals between field contamination events and planting or harvesting of fresh-cut produce crops.