In vitro antagonistic potential of gut bacteria isolated from indigenous honey bee race of Saudi Arabia against Paenibacillus larvae

Paenibacillus larvae is one of the major bacterial pathogens of honey bee broods and the causative agent of American foulbrood (AFB) disease. The factors responsible for the pathogenesis of AFB disease are still not fully understood, and the increasing resistance of P. larvae to commonly used antibiotics requires a search for new agents to control this disease. An in vitro screen was carried out to determine the antagonistic activity of gut bacteria isolated from indigenous honey bees, Apis mellifera jemenitica of Saudi Arabia against P. larvae. The gut bacterial isolates were evaluated individually against P. larvae ATCC9545 strain by the disc diffusion method. Seven of the 100 evaluated gut bacterial isolates, Fructobacillus fructosus (KY027123); Proteus mirabilis (KY027132); Bacillus licheniformis (KY027142); Lactobacillus kunkeei (KY027158); Bacillus subtilis (KY027169); Enterobacter kobei (KY027178); and Morganella morganii (KY027186) showed strong inhibitory effects. To our knowledge, this the first demonstration of antagonistic activity of F. fructosus, P. mirabilis, E. kobei, and M. morganii isolated from honey bee gut against P. larvae. The tested gut isolates exhibited significant antimicrobial activities against P. larvae, and they could play an important role in the treatment or prevention of AFB disease.