Melissococcus plutonius

Bee larvae become infected through feeding; Melissococcus plutonius multiplies in the larvae's midgut at the expense of food provided by nurse bees. If the larvae's food supply is limited, it can be almost entirely consumed by the pathogen, resulting in the larva's death by starvation. When food is abundant, the larva develops normally and, as a pupa, releases the infectious agent, which is spread to other larvae by nurse bees. The larvae, however, are destined to die: their bodies initially appear flaccid, then pale yellow, and then brown in the advanced stage.

Melissococcus plutonius can be grown on a suitable medium; Bailey's solution is generally used:

Values expressed in g/liter

• Yeast extract: 10
• Cysteine: 1
• Soluble starch: 10
• Potassium dihydrogen phosphate: 13.50
• Agar: 20
• Glucose (or fructose): 10

The pH must be adjusted to 6.6 before adding the agar. Glucose must be added aseptically after sterilizing the medium by microfiltration under a biological hood.

The medium must be autoclaved at 116°C for 15 minutes.

Melissococcus plutonius is easily isolated by embedding it in Petri dishes containing Bailey's solution, kept liquid at 45°C. The Petri dishes should be placed in anaerobic jars and incubated in a thermostat at 35°C. After about 4 days, colonies of Melissococcus plutonius will appear.

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