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High-level resistance of Melissococcus plutonius clonal complex 3 strains to antimicrobial activity of royal jelly
Daisuke Takamatsu1,2, Aya Osawa3, Keiko Nakamura4
1Division of Bacterial and Parasitic Disease, National Institute of Animal Health, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan.
Abstract:
Melissococcus plutonius is the causative agent of European foulbrood of honey bee larvae. Among its three genetically distinct groups (CC3, CC12 and CC13), CC3 strains have been suggested to be more virulent at the colony level. Honey bee larvae are fed royal or worker jellies by adult bees, and these jellies exhibit antimicrobial activity. Since M. plutonius orally infects larvae via brood food, we herein investigated the resistance of M. plutonius to the antimicrobial activity of royal jelly (RJ). The results obtained revealed that M. plutonius strains were more resistant to RJ and its component, 10-hydroxy-2-decenoic acid, than the other species tested. Moreover, among the M. plutonius strains examined, CC3 strains exhibited the strongest resistance to antimicrobial activity; they temporarily proliferated and survived for a long period in 50% RJ-containing broth. However, resistance was not observed when freshly cultured bacteria were used, it was only detected after a preculture on agar media for five or more days, suggesting that, under certain conditions, CC3 strains change their physiological state to that which is advantageous for survival in brood food. This high-level RJ resistance of CC3 strains may contribute to their virulence in the field.
Insights
Melissococcus plutonius, the cause of European foulbrood, shows high resistance to antimicrobial royal jelly. More virulent CC3 strains exhibit the strongest resistance, potentially explaining their field impact.
Area of Science:
- Apiculture
- Microbiology
- Insect Pathology
Background:
- Melissococcus plutonius causes European foulbrood in honey bee larvae.
- Honey bee larvae are fed brood food, which possesses antimicrobial properties.
- CC3 strains of M. plutonius are considered more virulent.
Purpose of the Study:
- To investigate the resistance of M. plutonius to the antimicrobial activity of royal jelly (RJ).
- To compare the RJ resistance among different genetic groups of M. plutonius.
- To understand the physiological basis for RJ resistance in M. plutonius.
Main Methods:
- Testing the antimicrobial activity of RJ and 10-hydroxy-2-decenoic acid against M. plutonius.
- Comparing the resistance of M. plutonius strains (CC3, CC12, CC13) to RJ.
- Investigating the effect of preculture conditions on M. plutonius RJ resistance.
Main Results:
- M. plutonius strains demonstrated greater resistance to RJ and 10-hydroxy-2-decenoic acid compared to other tested species.
- M. plutonius CC3 strains showed the highest resistance to RJ's antimicrobial activity.
- RJ resistance in CC3 strains was observed after prolonged preculture, suggesting a physiological adaptation.
Conclusions:
- M. plutonius, particularly CC3 strains, possesses significant resistance to royal jelly's antimicrobial properties.
- This resistance is likely a physiological adaptation that enhances survival in brood food.
- The high RJ resistance of CC3 strains may correlate with their increased virulence in honey bee colonies.
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