Evaluating the Effectiveness of Ultraviolet-C Lamps for Reducing Escherichia Coli: Distance and Exposure Time

An increasing number of healthcare-associated infections indicates a need to search for the ideal disinfection method. The high biocidal efficacy of the most common disinfection method, UV-C radiation, has been confirmed in laboratory conditions; however, the real biocidal has not been determined yet. UV-C radiation's effectiveness on surface disinfection was evaluated at different distances of bacterial samples (Escherichia coli) from UV-C lamps and exposure times of radiation. The results of microbiological tests were presented as changes in the colony-forming unit (CFU/mL) and average colony size (mean) under monitoring the radiation dose emitted by the radiation source. The highest percentage reduction of the CFU/mL (83%) was measured at a distance of 10 cm from the UV-C lamp (2 x 36 W253.7 nm), exposed to radiation for one hour. The UV-C radiation is ineffective at a distance higher than one meter on a porous surface, indicating a need for further studies on modifying this method.