THE EFFECT OF NEAR-ULTRAVIOLET LIGHT ON STAPHYLOCOCCI AND MYCOBACTERIA IN DROPLET NUCLEI.

Abstract

The bactericidal effect of near-ultraviolet light (3,200 to 4,000 A.U.) on organisms in aqueous suspension has been reported (1-3). However, to the writers' knowledge, there have been no studies of the antibacterial effect of light of such wave lengths on microorganisms in droplet nuclei. Because droplet nuclei are vehicles for the transmission of certain infectious agents, knowledge of the antimicrobial effects of light on microorganisms in air-borne particles is of interest. Although far-ultraviolet light (2,537 A.U.) has long been used for germicidal purposes, its pronounced toxic effect on human skin and eyes requires that use of ultraviolet light in these wave lengths be strictly limited to indirect irradiation. Near-ultraviolet light has little or no significant effect on the skin of persons who are not photosensitive (4); only very high intensities of near-ultraviolet light provoke an erythematous reaction in normal skin. However, certain abnormally sensitive persons and those who are under treatment with photosensitizing drugs are sensitive to even moderate intensities of this light. For this reason, even near-ultraviolet irradiation must be controlled. The purpose of this report is to describe the effects of near-ultraviolet light on staphylococci and on several strains of mycobacteria in droplet nuclei.