A comparative study of the effects of UVC irradiation on select procaryotic and eucaryotic wound pathogens

Managing wounds infected with a mixture of several types of microorganisms such as bacteria (procaryotes) and fungi (eucaryotes) is a challenging clinical situation. The purpose of this study was to determine the effectiveness of ultraviolet light (UVC) in eradicating select procaryotic and eucaryotic organisms, in both pure culture and mixed cultures in vitro. Five replications of each organism or mixture of organisms (10(6) organisms/mL singly or 10(15) organisms/mL mixed culture) were plated. The cultures were treated with a UVC light 1 inch from the surface. Irradiation times were 0, 2, 3, 4, 5, 15, 30, 45, 60, 90, 120, and 180 seconds. Bacterial cultures were incubated and colony counts performed. Upon exposure to UVC, a 99.9% kill rate was obtained at 3 to 5 seconds for the procaryotic organisms (Pseudomonas aeruginosa and Mycobacterium abscessus) tested. However, 15 to 30 seconds of UVC treatment was required to obtain 99.9% kill of the eucaryotic organisms (Candida albicans, Aspergillus fumigatus) tested. This study demonstrates a decreasing sensitivity of evolutionarily more complex organisms to UVC. This study also provides further evidence that short exposure times to UVC are detrimental to procaryotic and simple unicellular eucaryotic organisms while sparing more complex multicellular organisms.