Persistence of Escherichia coli O157:H7 in soil and on plant roots

Abstract

Soil microcosms were inoculated with Escherichia coli O157:H7 to test persistence in fallow soil, on roots of cover crops and in presence of manure. In fallow soils, E. coli O157:H7 persisted for 25-41 days, on rye roots for 47-96 days and on alfalfa roots, in a silt loam soil, for 92 days whereas on other legumes persistence ranged from 25-40 days, similar to fallow soil. Manure did not seem to affect the persistence of E. coli O157:H7 in these soils. Indigenous and manure-applied coliform populations often decreased faster when E. coli O157:H7 was applied, indicating possible competition between microflora. Coliform populations in microcosms not inoculated with E. coli O157:H7 decreased more slowly or increased. Microbial community analyses showed little effect for E. coli O157:H7 inoculation or addition of manure. Microbial community metabolic activity was enhanced from rye roots after 14 days and by 63 days from alfalfa roots. Microbial community lactose utilization increased over time on rye roots in all soils and on alfalfa roots in a silt loam soil when E. coli O157:H7 was inoculated. Lactose utilization also increased for uninoculated rye roots, soil around rye roots and in some fallow soils. Our data suggest that clay increases persistence and activity of E. coli O157:H7 and other coliforms. In frozen soil stored for over 500 days, E. coli O157:H7 was viable in 37% of tested samples. In summary, E. coli O157:H7 persisted longer and activity was enhanced with some cover crops in these soils due to plant roots, the presence of clay and freezing.

Investigation of Routes of Salmonella Contamination Via Soils and the Use of Mulch for Contamination Control during Lettuce Cultivation

“…These results indicate that lettuce grown in soil containing Salmonella or E. coli O157:H7 may become contaminated throughout the growing season. Gagliardi and Karns (2002) revealed that E. coli O157:H7 survived for 25 to 41 days in fallow Table 4. Effects of mulching and surface disinfection on Salmonella counts of lettuce cultivated in highly contaminated soil.…”

Wastewater reuse in irrigation: A microbiological perspective on implications in soil fertility and human and environmental health

“…A good example is the enterohemorrhagic strain E. coli O157:H7 that can be internalized into lettuce when exposed to contaminated irrigation water or soil (Solomon et al, 2002;Wachtel et al, 2002). Moreover, because plants are privileged hosts for these bacteria, if supplied in irrigation water, they can proliferate and survive for longer periods when plants are present than in their absence (Gagliardi and Karns, 2002;Ibekwe et al, 2004;Tyler and Triplett, 2008). Another risk is that bacteria transmitted by this pathway may be inherited through plant seeds, as has been described for some endophytic bacteria (Burnett et al, 2000;Cooley et al, 2003;Guo et al, 2001;Rosenblueth and Martínez-Romero, 2006;Tyler and Triplett, 2008;Wang et al, 2006).…”

Enterohaemorrhagic Escherichia coli: emerging issues on virulence and modes of transmission

“…Persistence of STEC in the soil [55,56] favours the infection of cattle and makes environmental exposure a risk factor for human infection [32,75,125,158]. Animal wastes and effluents from farming operations, including manure and slurries, are frequently applied as a fertiliser to land used for crop or silage production and cattle grazing.…”