Abstract
This study investigated (1) the susceptibility of Bacillus anthracis (Ames strain), Bacillus subtilis (ATCC 19659), and Clostridium sporogenes (ATCC 3584) spores to commercially available peracetic acid (PAA)- and glutaraldehyde (GA)-based disinfectants, (2) the effects that heat-shocking spores after treatment with these disinfectants has on spore recovery, and (3) the timing of heat-shocking after disinfectant treatment that promotes the optimal recovery of spores deposited on carriers. Suspension tests were used to obtain inactivation kinetics for the disinfectants against three spore types. The effects of heat-shocking spores after disinfectant treatment were also determined. Generalized linear mixed models were used to estimate 6-log reduction times for each spore type, disinfectant, and heat treatment combination. Reduction times were compared statistically using the delta method. Carrier tests were performed according to AOAC Official Method 966.04 and a modified version that employed immediate heat-shocking after disinfectant treatment. Carrier test results were analyzed using Fisher's exact test. PAA-based disinfectants had significantly shorter 6-log reduction times than the GA-based disinfectant. Heat-shocking B. anthracis spores after PAA treatment resulted in significantly shorter 6-log reduction times. Conversely, heat-shocking B. subtilis spores after PAA treatment resulted in significantly longer 6-log reduction times. Significant interactions were also observed between spore type, disinfectant, and heat treatment combinations. Immediately heat-shocking spore carriers after disinfectant treatment produced greater spore recovery. Sporicidal activities of disinfectants were not consistent across spore species. The effects of heat-shocking spores after disinfectant treatment were dependent on both disinfectant and spore species. Caution must be used when extrapolating sporicidal data of disinfectants from one spore species to another. Heat-shocking provides a more accurate picture of spore survival for only some disinfectant/spore combinations. Collaborative studies should be conducted to further examine a revision of AOAC Official Method 966.04 relative to heat-shocking.
Highlights
The decontamination efforts that followed the intentional release of Bacillus anthracis spores through the US Postal Service have generated significant interest in chemical disinfectants that are capable of inactivating spores from virulent strains of B. anthracis
MicrobiologyOpen published by John Wiley & Sons Ltd
Vegetative cultures of B. anthracis and B. subtilis were grown on Columbia agar (Becton, Dickinson and Company, Sparks, MD) and incubated under aerobic conditions, whereas vegetative cultures of C. sporogenes were grown on Reinforced Clostridial Agar (RCA, Becton, Dickinson and Company) and incubated under anaerobic conditions using an Anoxomat system (Advanced Instruments, Inc., Norwood, MA)
Summary
The decontamination efforts that followed the intentional release of Bacillus anthracis spores through the US Postal Service have generated significant interest in chemical disinfectants that are capable of inactivating spores from virulent strains of B. anthracis. Suspension tests were conducted, with and without heat-shocking, to obtain the inactivation kinetics for CIDEXTM, STERIPLEXTM HC, and STERIPLEXTM Ultra against spores from a fully virulent strain of B. anthracis as well as spores from well-characterized strains of Bacillus subtilis and Clostridium sporogenes These tests provided comparative data on the efficacy of the three disinfectants against the different spore species. They allowed the investigation of the effects of heatshocking (according to AOAC Official Method 966.04) on the viability of spores in suspension after treatment with glutaraldehyde and peracetic acid These tests revealed the consequences of heat-shocking on virulent strains of B. anthracis after disinfectant treatment. This allowed for the evaluation of the effects of a 3-week incubation period prior to heat-shocking that is prescribed by AOAC Official Method 966.04
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