Potentiating effects of manganese dioxide on experimental respiratory infections

Abstract

Single and multiple 3-hour-long exposures to manganese dioxide (MnO 2) aerosol in respirable particle size, altered the resistance to bacterial and viral pneumonias. Increased mortality rates and reduced survival times were observed in mice exposed daily for 3 or 4 days to MnO 2 aerosol and challenged with airborne Klebsiella pneumoniae within 1 hour of termination of the last aerosol exposure. When the interval between the exposure and challenge was extended to 5 hours, the altered resistance to infection was seen already after a single 3-hour-long exposure to MnO 2 aerosol. Mice infected with airborne influenza virus 24 or 48 hours before initiation of the MnO 2 exposures also showed increased mortality rates, reduced survival times, and increased pulmonary lesions. The effect was more pronounced in mice exposed to MnO 2 at 48 hours after the infectious challenge.