Abstract
Elimination of Bacillus anthracis spores from the environment is a difficult and costly process due in part to the toxicity of current sporicidal agents. For this reason we investigated the ability of the spore germinants L-alanine (100 mM) and inosine (5 mM) to reduce the concentration of peracetic acid (PAA) required to inactivate B. anthracis spores. While L-alanine significantly enhanced (p = 0.0085) the bactericidal activity of 500 ppm PAA the same was not true for inosine suggesting some form of negative interaction. In contrast the germinant combination proved most effective at 100 ppm PAA (p = 0.0009). To determine if we could achieve similar results in soil we treated soil collected from the burial site of an anthrax infected animal which had been supplemented with spores of the Sterne strain of B. anthracis to increase the level of contamination to 104 spores/g. Treatment with germinants followed 1 h later by 5000 ppm PAA eliminated all of the spores. In contrast direct treatment of the animal burial site using this approach delivered using a back pack sprayer had no detectable effect on the level of B. anthracis contamination or on total culturable bacterial numbers over the course of the experiment. It did trigger a significant, but temporary, reduction (p < 0.0001) in the total spore count suggesting that germination had been triggered under real world conditions. In conclusion, we have shown that the application of germinants increase the sensitivity of bacterial spores to PAA. While the results of the single field trial were inconclusive, the study highlighted the potential of this approach and the challenges faced when attempting to perform real world studies on B. anthracis spores contaminated sites.
Highlights
Anthrax, caused by the bacterium Bacillus anthracis, is primarily a disease of animals which can infect humans through contact with infected animals and their products, or as a consequence of bioterrorism (Baillie, 2009)
In this study we examined the ability of germinants to potentiate the activity of peracetic acid (PAA) against B. anthracis spores in the laboratory and in a small field trial on an anthrax spore contaminated animal burial site in North East Turkey where the disease in cattle is endemic and contaminated land represents an ongoing source of infection (Doganay and Metan, 2009)
To determine the biocidal effect of the treatment during the contact period we assessed the ability of 0.5% (w/v) Sodium thiosulphate to neutralize the biocidal activity of 25000 ppm PAA
Summary
Anthrax, caused by the bacterium Bacillus anthracis, is primarily a disease of animals which can infect humans through contact with infected animals and their products, or as a consequence of bioterrorism (Baillie, 2009). The very properties which make B. anthracis an effective weapon, the ability to form chemically resistant spores, makes them extremely difficult to remove from a contaminated environment without recourse to toxic chemicals (Manchee et al, 1994; Schmitt and Zacchia, 2012). While the impact of toxic chemicals such as formaldehyde and chlorine dioxide can be controlled and mitigated within confined areas such office buildings, the same cannot be said for large urban spaces such as major transport hubs and city streets. The successful decontamination of 4 hectares of B. anthracis spore contaminated land on Gruinard Island, an uninhabited island located off the coast of Scotland which was contaminated by the military during World War 2 required the application of 2 million liters of 5% formaldehyde in sea water (Manchee et al, 1994). The release of a similar volume of toxic chemical in a major urban center could cause considerable environmental damage
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