Decay of Salmonella enterica ,Escherichia coli and bacteriophage MS2 on the phyllosphere and stored grains of wheat (Triticum aestivum )

Abstract

Cereal crops grown in the biosolids-amended soil can potentially become contaminated with pathogenic micro-organisms during growth and at the time of harvesting. There is small but unquantified potential risk of transfer of enteric pathogens to humans and animals from contaminated plants and grains. This study examined decay of Escherichia coli, Salmonella enterica serovar Typhimurium and bacteriophage MS2 on the wheat phyllosphere and on stored grains. This was done to assess the health implications of cereal crops contaminated from land application of biosolids. E. coli, S. enterica and MS2 were inoculated onto the leaves, spikelets and grains of wheat. The change in the numbers of inoculated micro-organisms was determined over time to calculate the respective 90% reduction time (T90 ) in each of these environments. A rapid inactivation (T90 <1-3 days) of E. coli and S. enterica and MS2 from the plant phyllosphere was observed, particularly from the spikelets. The decay rates were influenced by micro-organism type and location on the plant phyllosphere. Decay times on the stored grains were longer (T90 9-71 days), with some observed influence of grain variety on pathogen decay times. Results of this study suggest that there is very limited potential of enteric pathogens survival on wheat phyllosphere and grains. Therefore, the risk of transfer of enteric pathogens from biosolids-amended soil to consumers of grain products is considered to be low. This study has important implications for the grains industry, as the results suggest that chances of preharvest contamination of grains with enteric pathogens from biosolids-amended soil are low.