Survival and persistence of nonspore-forming biothreat agents in water

To determine whether nonspore-forming biothreat agents can survive and persist in potable water that does not contain a disinfectant.

Autoclaved, de-chlorinated Atlanta municipal water was inoculated with eight isolates of bacterial biothreat agents (10⁶ CFU ml⁻¹). The inoculated water samples were incubated at 5, 8 (Francisella tularensis only) or 25°C and assayed for viability by culture and by the presence of metabolic activity as measured by esterase activity (ScanRDI, AES Chemunex). Viability as determined by culture varied from 1 to 30 days, depending upon the organism and the temperature of the water. All organisms were determined viable as measured by esterase activity for the entire 30 days, regardless of the incubation temperature.

Francisella tularensis was culturable for at least 21 days if held at 8°C. The remaining nonspore-forming bacterial biothreat agents were found to be metabolically active for at least 30 days in water held at 5 or 25°C.

The data can assist public health officials to determine the safety of drinking water after contamination with a biothreat agent.