Volume 17, Number 3, September 2005

Bactericidal Efficacy of Ultraviolet Irradiation on Staphylococcus aureus

Karlina Hardjawinata, Rina Setiawati, Warta Dewi

Department of Oral Biology, Faculty of Dentistry, Padjadjaran University, Bandung, Indonesia


Abstract
Objective: To determine the bactericidal effect of ultraviolet radiation on Staphylococcus aureus air contaminant for preventing airborne transmission.
Materials and Methods: The air of a dental clinic was sampled on settling plates to isolate Staphylococcus aureus. The suspension of
Staphylococcus aureus was irradiated with a 6-W ultraviolet lamp after 5, 10, 15, and 30 minutes, and 1, 2, 3, 4, and 24 hours. After every exposure time, 0.1 ml suspension was taken with a pipette and cultured on a sterile nutrient agar plate. This process was repeated by culturing 0.1 ml of Staphylococcus aureus suspension without ultraviolet radiation for a control. All cultures were incubated overnight at 37ºC, and the developed colonies were counted with a Stuart electrical bacteria colony counter.
Results: Ultraviolet radiation inhibited 89.1% of the colonies after 5 minutes, and 89.6% after 10 minutes. The number of colonies undergoing division diminished with longer irradiation times, and all bacteria were destroyed after 3 to 4 hours of radiation.
Staphylococcus aureus suspension without radiation showed an increase in 6.7% of the colonies after 5 minutes and an increase of 117.9% after 4 hours. A greater number of colony-forming units developed with longer exposure times.
Conclusions: Ultraviolet radiation has a bactericidal effect on
Staphylococcus aureus, even after exposure for 5 minutes. Therefore, ultraviolet radiation could be used to control the airborne transmission of Staphylococcus aureus in treatment areas such as dental clinics.

Key words:
Staphylococcus aureus, Ultraviolet rays

Asian J Oral Maxillofac Surg. 2005;17:157-161.
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