Study of the Bacteria Location in a Closed Chamber for Their Inactivation by High Ozone Concentration

Purpose

This paper is aimed to an experimental study carried out on a new sterilization technique with gaseous ozone produced inside an aluminum enclosure itself using ozone generating modules made of flat ceramic plates, reaching high concentrations exceeding 2000 ppm in about 1 min (theoretical value).

Methods

The sterilization procedure is performed in two successive steps starting by the production of ozone inside the enclosure and followed by a destruction step using heating resistors for increasing the temperature inside the sterilizer up to 60 °C. It was found that a total duration including 3 min for the first step (ozonation time) and 20 min for the second step (destruction time) is optimal.

The bactericidal effects of high ozone concentrations have been tested against four types of bacteria and a single type of fungus, respectively: Escherichia coli ATCC25922, Staphylococcus aureus ATCC 25,923, Bacillus cereus ATCC 11,778, Pseudomonas aeruginosa ATCC27853, and Candida albicansATCC1023.

Results

The destruction of ozone inside the enclosure is ensured by electrical heating resistors at a temperature range lying between 55 and 60 °C for an average duration of 20 min. The bacterial suspensions studied contain on average about 106 CFU/ml before the treatment and become equal to zero after sterilization, with better efficacy against E. coli due to its thinner cell surface structure. Moreover, for the fungus sample, after only 60 s of ozonation, a fungal disappearance was clearly observed. A sterilization rate greater than 99.99% was obtained for the five different species of bacterium.

Conclusion

The microbiological results indicated that the use of the gaseous ozone produced inside with a high concentration (2000 ppm/min) eliminates the various bacteria and fungi studied in a short time. Ozonation appears to be a good alternative for the sterilization of medical-surgical devices.

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