Microorganism Inactivation by Ozone Dissolved in Aqueous Solution: A Kinetic Study Based on Bacterial Culture Lipid Unsaturation

Abstract

Physiological solutions ozonated are widely used in the medical field (dentistry and surgery) as an effective bactericide. In this investigation, the inactivation of Escherichia coli and Pseudomonas aeruginosa by ozone dissolved in physiological solution was studied. There is a poor knowledge of the inactivation efficiency of this solution for different bacteria. The efficiency of the microorganisms’ inactivation was evaluated by the total unsaturation of lipids measured by the so-called Double Bond Index (DB-index). This is a sensitive analysis to evaluate the quantity of carbon-carbon double bonds (>C=C<) available in organic and biological samples, with high efficiency and in a short time. DB-index results were compared with the quantity of colony forming units (CFU) available in the culture. Three experimental systems were evaluated to determine the relationship between the DB-index variable and the microorganism’s inactivation: 1) using BHI agar as a culture medium to evaluate the dynamic growing curve when the ozone dissolved was dosed over the strain’s surface; 2) using a glucose solution (5%) as culture media and keeping the ozone concentration constant, which was dissolved in different physiological solutions, to observe the effects of solvent type over the bacteria growth; and, 3) using a glucose solution (5%) as culture media, and physiological solution of NaCl (0.9%) as a dissolved media for ozone at different concentrations. From the experimental data, a model of the ozone inactivation of each pathogen was built to obtain the inactivation kinetics. The model obtained showed a correlation between the CFU behavior and DB-index to each bacteria, since Pseudomona aeruginosa was more resistant to being oxidized than Escherichia coli.