Alkali-induced revival of Bacillus spores after inactivation by glutaraldehyde

Spores of Bacillus subtilis 168 were apparently fully inactivated by exposure to 2% (w/v) glutaraldehyde for 20 h but a few spores could be revived by further treatment with 10-100 mM NaOH. A similar effect was found with spores from a range of Bacillus species. A minimum concentration of 5% (w/v) glutaraldehyde was required to prevent the alkali-induced reactivation. The implications of these results for the use of glutaraldehyde as a sporicidal agent are discussed.