Abstract
A pure culture of Streptococcus pluton isolated in Denmark from larvae there with European foul brood (E.F.B.) caused the disease when inoculated into healthy colonies. Bacteria-free filtrates of E.F.B, larvae from either Denmark or England did not cause E.F.B., and the English filtrate did not contain the virus-like particles seen in similar filtrates elsewhere. All strains of S. pluton examined, which had been isolated in many parts of the world, were closely related serologically. Inoculating colonies with bacteria from E.F.B, larvae did not cause E.F.B, during late summer, and endemically diseased colonies recovered spontaneously when removed to areas usually free from E.F.B.