Screening additional antibiotics for efficacy against American foulbrood

Abstract

SUMMARYThe sensitivity of Paenibacillus larvae larvae (American foulbrood, AFB) to 35 antibiotics and synthetic antimicrobials, including two previously reported, was investigated. All compounds but one are currently approved by the US Food and Drug Administration for agricultural uses. The most active approved antibiotics screened were pirlimycin, tiamulin, and the polyether ionophores, particularly narasin, lasalocid, salinomycin, laidlomycin, and maduramicin. Pirlimycin and tiamulin show high activity in vitro, but share the mode of action of tylosin and lincomycin (inhibition of ribosomal peptide synthesis), and therefore have no advantage over it. While the ionophores have high in vitro activity and a completely different mode of action (interference with cation transport across cell membranes) and therefore seemed to represent potential alternative treatments for AFB, they were inactive in the field.