Quantitative tyramine analysis method for Apis mellifera larvae infected with Melissococcus plutonius, the causative
Daisuke Takamatsu1,2,3, Ryuichi Uegaki4, Mariko Okamoto1
1Division of Infectious Animal Disease Research, National Institute of Animal Health, National Agriculture and Food Research Organization, Ibaraki, Japan.
Abstract:
Tyramine, a trace monoamine produced from tyrosine by decarboxylation and found naturally in foods, plants, and animals, is a suspected virulence factor of Melissococcus plutonius that causes European foulbrood in honey bee brood. In the present study, we developed a method for quantitative analysis of tyramine in culture medium and honey bee larvae with a limit of quantitation of 3 ng/mL and a recovery rate of >97% using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry and deuterium-labeled tyramine, demonstrating for the first time that a highly virulent M. plutonius strain actually produces tyramine in infected larvae. This method will be an indispensable tool to elucidate the role of tyramine in European foulbrood pathogenesis in combination with exposure bioassays using artificially reared bee larvae.
