Homeland Security Research

Research Highlights

Anthrax Surrogates Used in Chlorine Inactivation Study

EPA is responsible for protecting drinking water systems and sources. In carrying out these responsibilities, EPA conducted research on the use of nonvirulent surrogates for Bacillus anthracis in inactivation studies involving chlorination.

Research

In the study, EPA evaluated the use of Bacillus globigii as a surrogate for the virulent strain Bacillus anthracis. The testing specifically evaluated the inactivation by chlorination of Bacillus globigii relative to other Bacillus species. Recently approved legislation limits the use of Bacillus anthracis spores to laboratories that have governmental approval for working with select agents. These restrictions have prompted renewed interest in evaluating organisms that might serve as surrogates for the overt pathogen.

Results and Conclusions

The study compared the resistance of B. globigii with that of other Bacillus strains. The results are shown as CT values; “C” is the concentration of chlorine in milligram/liters (mgL), and “T” is exposure time in minutes. The mean CT values of B. anthracis Sterne, B. cereus, B. thuringiensis (Rice et al. 2005), and the virulent B. anthracis Ames strain (Rose et al. 2004) are shown in a table in the attached Technical Brief. The mean CT values for B. globigii are relatively higher than the corresponding mean CT values of the three surrogates and the virulent strain, indicating that spores of B. globigii are more resistant than the spores of the other Bacillus species studied. Thus, B. globigii can serve as a conservative surrogate for B. anthracis during studies of inactivation by chlorination.