Surviability ofListeria monocytogenes in agricultural field soil

Survivability of Listeria monocytogenes in clay loam soil was examined at 30° C for a period of 35 days. The microorganism inoculated in soil steadily declined from 3.5 × 10⁶ g⁻¹ to 3.9 × 10⁴ g⁻¹ (P = 0.05) on 35^th days. Destruction ofnormal soil microflora by heat treatment resulted in marginal rise in 3.3 × 10⁶ g⁻¹ of L. monocytogenes to 4.2 × 10⁶ g⁻¹ during the first 7 days, followed by steady decline to 5.6 × 10⁴ g⁻¹ on 35^th days. Heat treated soil inoculated with lower concentration of L. monocytogenes (3.6 × 10⁴ g⁻¹) supported sharp rise in its population to 4.8 × 10⁶ g⁻¹ (P=0.05) during the first weak which gradually declined, but remained higher (6.1 × 10⁴ g⁻¹) than the initial load even on 35^th days. In non-sterile soil, the rise was less appreciable but L. monocytogenes maintained its levels (10⁴ g⁻¹) during the experimental period. Survivability of the microorganisms was also observed in the soil with added chicken manure, cattle manure or sheep/goat manure.