Examination of factors for use as potential predictors of human enteric pathogen survival in soil.
OBJECTIVE
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.


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.


CONCLUSIONS
This study provided evidence of specific properties that impact inactivation of E. coli O157:H7 and Salmonella in soils at 25°C.


CONCLUSIONS
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.
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.
M C
MC
Erickson
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.|Department of Crops and Soil Science, University of Georgia, Griffin, GA, USA.
M Y
MY
Habteselassie
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.
J
J
Liao
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.
C C
CC
Webb
Department of Crops and Soil Science, University of Georgia, Griffin, GA, USA.
V
V
Mantripragada
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.
L E
LE
Davey
Department of Food Science and Technology, Center for Food Safety, Griffin, GA, USA.
M P
MP
Doyle
D000818:Animals; D044822:Biodiversity; D018533:Biomass; D015169:Colony Count, Microbial; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D004553:Electric Conductivity; D019453:Escherichia coli O157 / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D008954:Models, Biological; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis; D012475:Salmonella / Q000502:physiology*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014510:Urease / Q000032:analysis; D014867:Water / Q000378:metabolism; D001617:beta-Glucosidase / Q000032:analysis
D021903:DNA, Ribosomal Spacer; D012987:Soil; D014867:Water; D010744:Phosphoric Monoester Hydrolases; D001617:beta-Glucosidase; D014510:Urease
E. coli O157:H7; Salmonella; microbial diversity; soil