Effect of sunlight on the survival of Salmonella on surfaces

Aims: To investigate the effect of simulated full-spectrum tropical sunlight on the survival of Salmonella in droplets on surfaces. Materials and Results: The survival on surfaces of three Zambian strains of Salmonella enterica serovars Enteritidis and Heidelberg was compared with that of a strain of S. enterica serovar Enteritidis phage type (PT) 4 with known characteristics which had been isolated from poultry in the UK. Samples were taken from surfaces every hour for 3 h and after 24 h exposure in either dark or 12 h light/12 h dark cycle conditions. Differences were analysed for significance using a one-way analysis of variance (ANOVA). Results show that there were a significantly higher number of cells surviving on surfaces after 24 h in the dark when compared with populations exposed to a 12 h light/12 h dark cycle. Significantly more cells also survived exposure to sunlight under dirty than clean conditions. Conclusions: Exposure to sunlight results in a significant decrease in numbers of Salmonella on surfaces. Significance and Impact of the Study: Under field conditions exposure of contaminated surfaces to sunlight could be used in place of chemical methods of control as a cheaper way to reduce Salmonella contamination of surfaces.