Select Agent Determination Concerning Coxiella burnetii Phase II, Nine Mile Strain, Plaque Purified Clone 4 With Reversion to Wildtype cbu0533

The Centers for Disease Control and Prevention (CDC), located within the Department of Health and Human Services (HHS), has determined that an excluded attenuated strain, Coxiella burnetii Phase II, Nine Mile Strain, plaque purified clone 4, has, in one instance, been shown to spontaneously mutate when passaged in vivo. The resulting mutant, C. burnetii Phase II, Nine Mile Strain, plaque purified clone 4 with reversion to wildtype cbu0533, has enhanced pathogenicity and virulence. Therefore, C. burnetii Phase II, Nine Mile Strain, plaque purified clone 4 with reversion to wildtype cbu0533 is not an excluded strain but is a select agent and subject to the HHS select agent and toxin regulations.