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 10moll(-1), irradiated by green LED ((max) 490-570nm) for 5, 10 and 15min and the cellular viability was determined. Pseudomonas aeruginosa was completely inactivated when treated with 10moll(-1) eosin Y for 10min. 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 5moll(-1) and 5min 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.