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Inactivation of Escherichia coli and Staphylococcus aureus by ultrasound
Nüzhet Cenk Sesal1, Özge Kekeç2
1Department of Biology, Arts and Science Faculty, Marmara University, Istanbul, Turkey. csesal@marmara.edu.tr.
Objectives:
The aim of this study was to obtain valuable information about the effect of ultrasonic irradiation with a frequency of 30 kHz frequency and power of 100 W on the inactivation capability of two bacterial groups, namely, Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923, in physiologic water samples.
Methods:
Ultrasonic irradiation of bacterial samples with different populations of 5 × 10(3), 1.5 × 10(4), and 3 × 10(4) colony-forming units/mL was performed at a constant frequency with various treatment times. The specific energy (γ) values were calculated for these different concentrations of E coli and S aureus. The rate constant for ultrasonic inactivation was estimated in the linear region of a plot representing a survival ratio logarithm versus sonication time.
Results:
Although a significant death rate for E coli was observed with ultrasound treatment, in contrary to expectations, an increase in S aureus populations was observed.
Conclusions:
Considering the widespread use of ultrasound for sterilization of tools and equipment used in hospitals, the results obtained in this study indicate that ultrasonic irradiation is not a suitable method for the elimination of the major hospital pathogen S aureus.
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