In the fall of 2001, letters laced with anthrax spores were delivered to various news organizations in New York and Florida, as well as to two Senators in Washington, D.C. Over 22 anthrax infections and five deaths resulted from exposure to these spores, and decontamination of the affected buildings was both time consuming and costly. Since these attacks, interest in sporicidal disinfectants has increased greatly. Many chemical sporicidal disinfectants are available commercially, but the exposure time required to sterilize can be relatively long. In addition, some spores are simply injured or inhibited by chemical disinfectants, but not necessarily killed. Studies have shown that heat shocking spores after exposure to some disinfectants can aid in the recovery of injured spores, but these studies have not evaluated this effect on spores exposed to peracetic acid-based disinfectants. Recently, our lab has evaluated two novel peracetic acid-based chemical disinfectants, PeraDox™ and PeraDox Ultra™ for their activity against a variety of bacterial agents. Results indicated that the PeraDox™ solutions had extremely rapid cidal activity on a wide variety of microorganisms, especially those with innate germicide resistance, such as bacterial endospores. However, possible recovery of these spores after heat shock was not evaluated. The purpose of this study was to compare the sporicidal activity of three disinfectants: CIDEX™, PeraDox™, and PeraDox Ultra™ on three species of spores (Bacillus subtilis, Bacillus anthracis, and Clostridium sporogenes) in suspension, with and without heat shocking. Spores in suspension were exposed to disinfectants for specified times and assayed for viable spores. These spore suspensions were then heat shocked (80 ºC for 20 min) and assayed again. After exposure to peracetic acid-based disinfectants and subsequent heat shock, some B. subtilis spores recovered, resulting in up to a one log difference in viable spores. Other species and disinfectants did not show this effect. In addition, the activity of these disinfectants on spores dried onto a surface was evaluated using the standard AOAC sporicidal test. The current AOAC test specifies heat shocking after three weeks of incubation. In this study, we evaluated the AOAC sporicidal test by heat shocking immediately following disinfection and after three weeks of incubation as prescribed. Carrier tests showed a greater number of positive B. subtilis carriers when heat shocked immediately following PeraDox™, and PeraDox Ultra™ treatment, than when carriers were heat shocked after three weeks. In summary, results showed that heat shocking increases resuscitation of spores treated with some disinfectants, but not others. Spores in suspension and those dried onto carriers responded similarly to heat shocking. Finally, PeraDox™ formulations had surprisingly rapid sporicidal kinetics.



College and Department

Life Sciences; Microbiology and Molecular Biology



Date Submitted


Document Type





disinfectant, sporicide, PeraDox, CIDEX, heat shock



Included in

Microbiology Commons