The pathogenicity of Paenibacillus larvae subsp. larvae spores and vegetative cells to honey bee (Apis mellifera) colonies and their susceptibility to royal jelly

SUMMARY

Vegetative Paenibacillus larvae subsp. larvae cells cultured on sheep blood agar were unable to cause American foulbrood (AFB) when sprayed on the young brood of nine nucleus colonies. However, a mixture of primarily vegetative cells and P. I. larvae spores (1.0 × 10⁶ spores) caused AFB in three of four inoculated colonies. AFB was also induced by spraying young brood with spores extracted from scales or spores cultured artificially. Although the pH environment of royal jelly was lethal to P. I. larvae vegetative cells in 20 min, royal jelly killed vegetative cells within 5 min. Royal jelly had no effect on the survival of P. I. larvae spores.

Keywords:

• Paenibacillus larvae larvae
• American foulbrood
• Apis mellifera
• honey bee brood
• pathogenicity
• spores
• vegetative cells
• royal jelly