B. anthracis Ames Strain

The Ames strain is one of 89 known strains of the anthrax bacterium ( Bacillus anthracis ). It was isolated from a diseased 14-month-old Beefmaster heifer that died in Sarita, Texas in 1981. The Ames strain came to wide public attention in association with the 2001 anthrax attacks. Seven letters mailed to media outlets and US Senators on September 18, 2001 and October 9, 2001 contained anthrax bacteria of this particular strain. This strain is a monomorphic disease, mutating slowly if at all. Because of its virulence, the Ames strain is used by the United States as somewhat of a gold standard for development of vaccines and testing their effectiveness, starting in the 1980s, after work on weaponizing the Vollum 1B strain ended and all weaponized stocks were destroyed after the end of the US biological warfare program in 1969.