Abstract
The biological properties and susceptibility to antimicrobial agents of Bacillus larvae were examined. Twenty-nine strains, 28 isolates from each outbreak of American foulbrood in Japan and a B.larvae type strain (ATCC 9545T) were used. Our B.larvae isolates had almost the same biological properties as the type strain. The isolates were more susceptible to penicillins, macrolides and lincomycin, a lincosamide, than other antimicrobials. Mirosamicin among the macrolides and ampicillin among the penicillins appeared to be the most effective agents.