Identification of Bacillus anthracis by API tests.

API and morphological tests were examined for their ability to distinguish between 37 Bacillus anthracis strains (virulent and avirulent) and 194 strains of closely related Bacillus species (B. cereus, B. mycoides and B. thuringiensis). In addition, 34 strains of B. anthracis and four of B. cereus were tested by several other methods that included capsule formation, ability to grow on a selective medium, and sensitivity to phage. It was found that virulent strains of B. anthracis were easily separated from the closely related Bacillus species by most of the test methods; but separation of slightly virulent and avirulent strains of B. anthracis from the closely related species could be done only by API and phage-sensitivity tests.