Application of mathematical models for bacterial inactivation curves using Hypericin-based photosensitization

The aim of this study was to evaluate which of the three mathematical models (Weibull, Geeraerd and Logistic) makes the best approximation for Hypericin-based photosensitization bacterial inactivation.

The inactivation of common food-borne pathogens Listeria monocytogenes and Bacillus cereus has been analysed. Three models, Weibull, Logistic and Geeraerd, have been used for different treatment conditions (10(-7 ) mol l(-1) and 10(-8)  mol l(-1) Hypericin concentrations and 2 and 60 min incubation time). The Logistic method showed better correspondence (estimated R(2)  ≥ 0·98, RMSE ≤ 0·41), than the Weibull (estimated R(2)  ≥ 0·91, RMSE ≤ 0·90) and the Geeraerd model (R(2)  ≥ 0·83, RMSE ≤ 1·27). After evaluation of best fitting model for the dependence of bacterial population reduction on irradiation time, the parameters describing treatment efficiency have been calculated.

Our results indicate that the Logistic model described in the best way the inactivation of B. cereus and L. monocytogenes by Hypericin-based photosensitization.

This study identified a best model for describing bacterial inactivation by hypericin-based photosensitization, which provides a way to evaluate the efficacy of different treatment conditions for this novel decontamination technique.