Decontamination Options for Bacillus anthracis -Contaminated Drinking Water Determined from Spore Surrogate Studies

Abstract

Five parameters were evaluated with surrogates of Bacillus anthracis spores to determine effective decontamination alternatives for use in a contaminated drinking water supply. The parameters were as follows: (i) type of Bacillus spore surrogate (B. thuringiensis or B. atrophaeus), (ii) spore concentration in suspension (10 2 and 10 6 spores/ml), (iii) chemical characteristics of the decontaminant (sodium dichloro-S-triazinetrione dihydrate [Dichlor], hydrogen peroxide, potassium peroxymonosulfate [Oxone], sodium hypochlorite, and VirkonS), (iv) decontaminant concentration (0.01% to 5%), and (v) exposure time to decontaminant (10 min to 1 h). Results from 138 suspension tests with appropriate controls are reported. Hydrogen peroxide at a concentration of 5% and Dichlor or sodium hypochlorite at a concentration of 2% were highly effective at spore inactivation regardless of spore type tested, spore exposure time, or spore concentration evaluated. This is the first reported study of Dichlor as an effective decontaminant for B. anthracis spore surrogates. Dichlor's desirable characteristics of high oxidation potential, high level of free chlorine, and a more neutral pH than that of other oxidizers evaluated appear to make it an excellent alternative. All three oxidizers were effective against B. atrophaeus spores in meeting the EPA biocide standard of greater than a 6-log kill after a 10-min exposure time and at lower concentrations than typically reported for biocide use. Solutions of 5% VirkonS and Oxone were less effective as decontaminants than other options evaluated in this study and did not meet the EPA's efficacy standard for a biocide, although they were found to be as effective for concentrations of 10 2 spores/ml. Differences in methods and procedures reported by other investigators make quantitative comparisons among studies difficult.Developing a decontamination approach that can be safely and effectively applied to civilian water resources and facilities following a terrorist or catastrophic release of Bacillus anthracis spores poses many challenges. For example, if a municipal drinking water system were contaminated directly or indirectly during or after such an incident, it would be essential to assess the potential health risks posed by water consumption or other water uses (e.g., recreational and bathing) and then to apply one or more proven technologies, if deemed necessary, to decontaminate the water supply quickly and cost-effectively. Treatment of drinking water implies the use of a decontamination approach that would not pose adverse health risks to humans or result in unacceptable damage to the environment.

Inactivation ofBacillusspores in decontamination wash down wastewater using chlorine bleach solution

“…Thus, for the remainder of experiments in the study, the rate of inactivation was measured at various levels of bleach alone, i.e., without vinegar for pH adjustment, in wastewater matrices to determine whether there was a minimum level of bleach that would yield complete inactivation. The elimination of vinegar is supported by literature cited earlier (Sabbah et al 2010 andRaber andBurklund 2010). The latter showed comparable inactivation using 3.3% bleach at 30 min contact time and no pH adjustment, which resulted in a solution pH comparable to values reported in this article under similar conditions.…”

“…Bacillus spores are highly resistant to disinfection Raber and Burklund 2010). Various decontamination agents such as bleach solution, liquid chlorine dioxide, electrochemicallygenerated chlorine dioxide, peracetic acid, hydrogen peroxide, gluteraldehyde, and formaldehyde have been reported to inactivate Bacillus spores (Sagripanti and Bonifacino 1996;Rice et al 2005;Majcher et al 2007;Raber and Burklund 2010;Buhr et al 2011).…”

“…Various decontamination agents such as bleach solution, liquid chlorine dioxide, electrochemicallygenerated chlorine dioxide, peracetic acid, hydrogen peroxide, gluteraldehyde, and formaldehyde have been reported to inactivate Bacillus spores (Sagripanti and Bonifacino 1996;Rice et al 2005;Majcher et al 2007;Raber and Burklund 2010;Buhr et al 2011). Despite a number of available decontamination approaches for Bacillus spores, information on the efficacy of bleach solution is of particular interest because of its conventional application as a disinfectant, low cost, and wide availability.…”

“…Heninger et al (2009) reported using a 10% (v/v) bleach solution for complete inactivation (≥5 log 10 removal) of Bacillus spores for a 10 5 mL −1 concentration with a contact time of 20 min, and a contact time of 60 min was reported for complete inactivation (≥6 log 10 removal) of Bacillus spores for a 10 6 mL −1 concentration in deionized water in a laboratory study. Raber and Burklund (2010) reported complete inactivation of B. globigii spores at a concentration of 10 6 mL −1 in drinking water (using distilled water to minimize the concentration of organics) at 0.2% and 2% (w/v) sodium hypochlorite solution (3.3% and 33% bleach, respectively) at 30 min and 10 min contact time, respectively, without pH adjustment. Most of the studies reported in the literature examined the efficacy of different disinfectants for the decontamination of hard, non-porous surfaces and buffered tap water or distilled water.…”

Germinant-Enhanced Decontamination of Bacillus Spores Adhered to Iron and Cement-Mortar Drinking Water Infrastructures

“…acillus spores are resistant to disinfection and other inactivation methods compared to vegetative bacteria (16,18,19,28). Spores can be used as a benchmark for decontamination of biological agents, including biothreat agents such as Bacillus anthracis, from drinking water infrastructures.…”