Effect of Humidity on Sporicidal Activity of Iodine Vapor on Bacillus thuringiensis

Abstract

The emergence of Bacillus anthracis as a potential bioterrorism and biological warfare agent points to the need for safe, effective, and economical sporicides for infection prevention and control. This work examined the efficacy of iodine vapor decontamination technologies to inactivate a surrogate for B. anthracis, Bacillus thuringiensis spores on glass materials. 10-10 colony-forming units of spores inoculated onto circular glass cover slips were treated with different concentrations of iodine vapor under various temperature and relative humidity. Only minimal spore killing activity was observed at low humidity. Higher humidity levels, as well as pre-hydration or post-hydration of the spores, increased the rate of inactivation as long as the contact between spores and iodine was maintained in a hydrated environment. Significant sporicidal activity of 3-log and 6-log spore reduction has been observed with 2.1 mg L iodine vapor concentration at 90% relative humidity and 22 °C, with 1 and 24 h of exposure, respectively. The results showed that the relative humidity of the environment is of major importance in regulating the rate at which the spores are inactivated by iodine. The results of this study may provide insight into the parameters of effective decontamination procedures for Bacillus spores using gaseous iodine.

Mechanisms of killing of Bacillus thuringiensis Al Hakam spores in a blast environment with and without iodic acid

“…However, spores are often stored dry and the mechanism whereby dry Bacillus spores are killed can differ from that for wet spores (Setlow et al ). Various chemicals, in particular compounds containing iodine, greatly accelerate spore killing (Grinshpun et al ; Wang et al , ; Li et al ; Gottfried et al ; Jiang et al ). In the current work, dry spores of the B. anthracis spore surrogate, Bacillus thuringiensis Al Hakam (BtAH), were exposed to explosive fireballs in a detonation chamber, with the fireball generated by explosively dispersed Al powder and with or without HIO 3 incorporated into the fireball, as the addition of the latter would likely increase spore killing.…”