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CHLORINE INACTIVATION OF BACILLUS ENDOSPORES
Citation:
Adcock*, N J., E W. Rice*, L A. Boczek*, AND M Sivaganesan*. CHLORINE INACTIVATION OF BACILLUS ENDOSPORES. Presented at American Society for Microbiology General Mtg, Washington, DC, 05/18-22/2003.
Description:
The possibility of a bioterrorism event resulting in the release of Bacillus anthracis endospores into a drinking water distribution system necessitates research into means by which these endospores can be inactivated. This study was designed to determine the chlorine resistance of various species and strains of Bacillus endospores suspended in water. Endospores from two strains of B. cereus and from one strain of B. thuringiensis were tested. Experiments were performed in triplicate at 5 C and at 23 C in chlorine demand-free buffer at pH 7 or pH 8 with free chlorine concentrations of 2.1 +/- 0.5mg/L. Endospores were added to constantly stirring chlorinated buffer, and samples were removed and neutralized at fixed intervals. Organisms were assayed by the membrane filtration procedure using nutrient agar. Inactivation rates were consistently slower at pH 8 than at pH 7 and at 5 C than at 23 C. Endospores of B. cereus strains were the most susceptible to chlorine under each condition and endospores of B. thuringiensis were the most resistant under each condition. Under the most favorable conditions in the study for chlorine inactivation with the most susceptible endospores, 20 minutes of exposure to 2mg/L of free chlorine was required for a 3 log inactivation. Under the least favorable conditions with the most resistant endospores, 6 hours of exposure to 2mg/L of free chlorine was required for a 3 log inactivation. These results were compared to chlorine inactivation data for endospores of B. anthracis from a study that was published in 1947. Under comparable study conditions, B. anthracis endospores were slightly more resistant to chlorination than endospores of strains of B. cereus and were less resistant than B. thuringiensis endospores. Because of their higher resistivity, B. thuringiensis endospores may serve as conservative surrogates for B. anthracis endospores