Reactive oxygen species are partially involved in the bacteriocidal actionof hypochlorous acid

Hypochlorous acid (HOCl) is probably the most widely used disinfectant worl dwide and has an important role in inflammatory reaction and in human resis tance to infection. However, the nature and mechanisms of its bactericidal activity are still poorly understood. Bacteria challenged aerobically with HOCl concentrations ranging from 9.5 to 76 mu M exhibit higher ability to f orm colonies anaerobically than aerobically, Conversely, aerobic plating gr eatly increased lethality after an anaerobic HOCL challenge, although anaer obic survival did not depend on whether HOCl exposure was aerobic or anaero bic, Even a short transient exposure to air after anaerobic HOCl challenge reduced anaerobic survival, indicative of immediate deleterious effects of oxygen, Exposure to HOCl can cause lethal DNA damage as judged by the fact that recA sensitivity to HOCl was oxygen dependent. Antioxidant defenses su ch as reduced glutathione and glucose-6-phosphate dehydrogenase were deplet ed or inactivated at 10 mu M HOCl, while other activities, such as superoxi de dismutase, dropped only above 57 mu M HOCl, Cumulative deficiencies in s uperoxide dismutase and glucose-6-phosphate dehydrogenase rendered strains hypersensitive to HOCl, This indicates that part of HOCl toxicity on Escher ichia coli is mediated by reactive oxygen species during recovery, (C) 1999 Academic Press.