Tuesday, July 31, 2007 - 10:25 AM
S68

Bacillus anthracis Spore Release in the Municipal Drinking Water Distribution System: Possible Scenarios

Jon J. Calomiris, Usanca, U.S. Army, 7150 Heller Loop, Fort Belvoir, Springfield, VA 22150-3198

Because bacterial spores are inclined to tolerate austere environments and disinfectants, Bacillus anthracis could pose a threat as a biological agent upon release in municipal drinking water systems. To understand the potential public health impact of the pathogen in drinking water distribution systems, B. anthracis spore transport through and survival in the pipe environment were investigated employing a model pipe system. Municipal chlorinated drinking water seeded with dormant B. anthracis spores was delivered to a pipe loop system and monitored by microscopic enumeration to determine spore densities of bulk water and pipe surfaces. Rate of spore attachment to pipe surfaces during 6-hours laminar flow was greater (up to about 4 fold) with (1) galvanized iron pipes as compared with copper or CPVC pipes and (2) pipes coated with biofilm created by a regulated flow of municipal chlorinated drinking water. Spore survival was demonstrated by maintenance of cultivability following 18-hours flow through copper pipes coated with biofilm. While spores remained viable at a typical free available chlorine residual (1 mg per liter), an elevated residual (5 mg per liter) as a single dose inactivated spores in pipe bulk water while a continual flow at the elevated residual was required to kill spores associated with pipe surfaces. Findings of this study could provide the basis for predicting the outcome of B. anthracis spore release in drinking water systems with respect to (1) spore contamination of pipe networks, (2) spore release at the consumer tap, and (3) spore tolerance to chlorine disinfection.

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