Erythrosine, also known as FD&C Red No. 3, is a synthetic dye that has been used for food coloring and dental plaque detection. The objective of this study was to evaluate erythrosine as a viable photosensitizer in photodynamic inactivation (PDI) of bacteria and yeast. Cells were treated with erythrosine with or without acetic acid in the presence and absence of light. Erythrosine in the absence of light did not show any activity against the microorganisms. When treated with light, erythrosine was efficient in eradicating non-adherent (planktonic) Gram (+) bacteria and yeast. However, Gram (-) bacteria were less responsive to PDI. Addition of acetic acid was found to enhance the activity of erythrosine and significantly lower the survival of Gram (-) bacteria. This study demonstrated the potential applications of erythrosine in PDI and the potentiating effects of acetic acid.

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