Combined effects of silver ions, UV radiation and/or high pressure on Bacillus subtilis spores

CHED 819

Audra MacNeil, Michael P. Labare, Lindsey Kracht, and Michael A. Butkus.
The bactericidal effects of silver ions have been known since the mid 1800s. Given contact times on the order of hours, silver has been shown to be somewhat effective as a disinfectant against bacteria and viruses. Our work has shown that the presence of 1.0 mg of Ag(I)/L for 24 hours did not inactivate Bacillus subtilis spores at an initial density of 1.8 x 108 cfu/mL. Previous work in our laboratory has shown a synergistic increase in the inactivation of viruses by using silver ions and UV radiation (Appl. Environ. Microbiol. 70:2848-2853 2004). We decided to test the combinations of silver ions with UV radiation and/or high pressures. Exposure to the same concentration of silver ion combined with UV radiation (40 mJ/cm2) did not inactivate the spores. Exposure to 0.1 mg of Ag(I)/L and 1000 psi for 30 minutes also did not inactivate the spores. Our future experiments will test a matrix of higher concentrations of silver ions, greater pressure, increase incubation periods and exposure to UV radiation.