Relationship of soil moisture to survival of Escherichia coli and Salmonella typhimurium in soils

Abstract

In a moist podzol type grey loam topsoil maintained under controlled conditions, persistence of inoculated Escherichia coli and Salmonella typhimurium cells was found to be similar with a death rate of about 14 days per log cycle. The death rate was not greatly affected by altering the growth conditions prior to inoculation of the soil. E. coli and S. typhimurium persistence was generally decreased in soil containing 85 % dry matter, with a rapid decline in cell numbers in soil containing more than 90% dry matter. E. coli survival was shown to be progressively reduced in soil: water mixtures containing less than 60% dry matter. Two of five different soil types tested were found to provide less favourable environments for inoculated cells, although soils of the same type collected on different occasions were not found to give consistent die-out rates. E. coli and S. typhzmurzum cells subjected to 14 days in dry soil were shown to have ability for regrowth when the soil was moistened.