Intranasal administration of DSM 32444 spores: safety and tolerability.

Administered nasally, spores of the Gram-positive bacterium have been shown to be able to induce innate immunity sufficient to confer protection to influenza and respiratory syncytial virus. Although members of the aerobiome, intranasal delivery of high numbers of live spores carries potential safety issues. To address the potential safety risk of using live spores, we assessed the safety of spores that had been completely inactivated using heat sterilization.