It is a Gram-positive, rod-shaped bacterium,[2] which forms spores which can remain viable for at least thirty-five years.

[4] In 1906, G.F. White first described the bacterium that caused American foulbrood (AFB), and named it Bacillus larvae.

[5] In 1950, a bacterium isolated from bee larvae and associated with the rare disease "powdery scale" was named Bacillus pulvifaciens by Katznelson.

[8] In 2006, the subspecies were eliminated based on spore morphology, biochemical profile and DNA testing, and when it was also demonstrated that experimental infection of honeybee larvae with the pulvifaciens subspecies caused American foulbrood signs without causing "powdery scale".

In contrast, genotypes ERIC III and IV are found in bacteriology archives and are considered practically unimportant.