Photodynamic inactivation of foodborne bacteria by eosin Y

Aims The aim of this study was evaluate the effect of photodynamic inactivation mediated by eosin Y in Salmonella enterica serotype Typhimurium ATCC 14028, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778. Methods and Results Bacteria (10 7 CFU per ml) were incubated with eosin Y at concentrations ranging from 0·1 to 10  μ mol l −1 , irradiated by green LED ( λ max 490–570 nm) for 5, 10 and 15 min and the cellular viability was determined. Pseudomonas aeruginosa was completely inactivated when treated with 10  μ mol l −1 eosin Y for 10 min. Treatments reduced B. cereus and Salm . Typhimurium counts to 2·7 log CFU per ml and 1·7 log CFU per ml, respectively . Escherichia coli counts were slightly reduced. Staphylococcus aureus presented the highest sensitivity, being completely inactivated by eosin Y at 5  μ mol l −1 and 5 min of illumination. The reduction of cellular viability of photoinactivated Staph. aureus was also demonstrated by flow cytometry and morphological changes were observed by scanning electron microscopy. Conclusions Eosin Y in combination with LED produced bacterial inactivation, being a potential candidate for photodynamic inactivation. Significance and Impact of the Study This study evidenced the efficacy of photodynamic inactivation as a novel and promising alternative to bacterial control.