Listeria monocytogenes survival in soil and incidence in agricultural soils

The effects of soil type, inoculum level, microbial competition, fertilizers, and carbon and nitrogen supplementation on Listeria monocytogenes survival in soil were examined by utilizing soil columns in ABS (acrylonitrile :butadiene styrene) plastic piping. Sandy soil yielded a lower level of L. monocytogenes survival than clay loam or sandy loam soils. L. monocytogenes numbers decreased from high inoculum levels, increased when inoculum levels were low, and reached higher levels more quickly in autoclaved soil. Soil amended with solid chicken manure supported a higher population than soil amended with either liquid hog manure or inorganic nitrogen-phosphorus-potassium fertilizer, but only when microbial competitors had been reduced. Carbon and nitrogen supplementation had no effect on the population of L. monocytogenes. In a field survey analyzed by using a 3-tube most probable number procedure with enrichment, Listeria spp. were present in 1 of 13 cultivated fields and 6 of the 13 surrounding uncultivated meadows.