Bactericidal effect of UVA combined with isothiocyanate on enteropatho-genic Escherichia coli and Vibrio parahaemolyticus

  Objective  To study bactericidal effect of ultraviolet A – light emitting diode (UVA-LED) irradiation combined with phytochemical of allyl isothiocyanate (AITC) on two diarrhea-causing pathogens.

  Methods  Two diarrhea-causing pathogenic bacteria, enteropathogenic Escherichia coli (ETEC) and Vibrio parahaemolyticus (VP), were used as the subjects. Bactericidal experiments in 3 × 2 factorial design were performed with the combined treatment of different concentrations of AITC and UVA_{365 nm}-LED irradiation; and the bacteria survival was assessed with colony form unit (CFU) and logarithm value of survival rate was calculated. The interactive effect of AITC and UVA_{365 nm}-LED irradiation was evaluated with analysis of variance for factorial design and illustrated with schematic diagram.

  Results  The bactericidal effect of AITC alone was gradually increased with the increment of concentration (P < 0.05). The effect of the combination of UVA-LED irradiation with AITC on the two pathogenic bacteria were statistically significant (P < 0.05). When UVA_{365 nm} irradiation was combined with 1 mg/ml AITC, the survive ratio of Vibrio parahaemolyticus was even reduced to – 6.15 lg.

  Conclusion  Synergistic bactericidal effect exists for combined treatment of UVA-LED irradiation and AITC on ETEC and VP.