Melissococcus plutonius
Cultural characteristics
Biochemical characters
Phylum Firmicutes, Class Bacilli, Order Lactobacillales, Family Enterococcaceae, Genus Melissococcus, Melissococcus plutonius corrig.
(ex White 1912) Bailey and Collins 1983, nom. rev., comb. nov., type species of the genus.
Old synonyms:
Streptococcus pluton (White 1912) Gubler 1954, Melissococcus pluton (ex White 1912) Bailey and Collins 1983.
Lancefield group D.
Gram-positive, lanceolate cocci, 0.5-0.7 x 1.0 µm, occuring singly, in pairs, or in chains of varying lengths. Non-motile. Non-spore-
forming. Non-acid-fast.
Colonies are usually up to 1 mm in diameter, opaque, white or granular, and
dome-shaped. Small, flat, transparent, umbonate colonies with clear centers and
granular peripheries have also been described. Grows on Bailey medium. No growth
on common nutrient media. Apart from yeast extract, the growth medium should
contain a fermentable sugar, starch, peptone, cysteine or cystine, and potassium. The
Na:K ratio required for growth is 1 or less. Optimum growth at 35 ºC, with some
strains growing between 20 and 45 ºC. Optimum pH is 6.5-6.6.
No aerobic growth. Anaerobic to microaerophilic, with best growth in the presence of
1-5% CO
2. Higher CO2 levels may inhibit some strains. Growth is greatly stimulated in
the presence of selfprepared autolyzed yeast extract. Nalidixic acid added to a final
concentration of 3 µg/ml, proved very selective for the isolation of
M. plutonius. Can
grow on TSA/B with defibrinated sheep blood (ATCC medium 260).
Isolated from diseased honeybee larvae - Apis mellifera and Apis cerana. Also isolated from the Varroa destructor mite.
Causative agent of European foulbrood of the honeybee. Dead larvae produce an odour of spoiled meat.
  1. Leon M. T. Dicks AND Wilhelm H. Holzapfel, 2009: Genus II. Melissococcus Bailey and Collins 1983, 672VP in Bergey’s Manual of
    Systematic Bacteriology, Second Edition, Volume Three, Vos, P.D.; Garrity, G.; Jones, D.; Krieg, N.R.; Ludwig, W.; Rainey, F.A.;
    Schleifer, K.-H.; Whitman, W.B. (Eds.), pp 607-611.
  2. Arai R, Tominaga K, Wu M, Okura M, Ito K, Okamura N, et al. (2012) Diversity of Melissococcus plutonius from Honeybee Larvae in
    Japan and Experimental Reproduction of European Foulbrood with Cultured Atypical Isolates. PLoS ONE 7(3): e33708. https://doi.
  3. Popa Al. 1965. Bolile albinelor si viermilor de matase. Ed. Agro-Silvica, Bucuresti.
  4. BacDive - the Bacterial Diversity Metadatabase. Sohngen C., Bunk B., Podstawka A., Gleim D., Vetcininova A., Reimer L.C.,
    Overmann J. Nucleic Acids Res. 2015. doi: 10.1093/nar/gkv983. Epub 2015 Sep 30. PMID: 26424852.
Some results are based on API 20 A and API rapid ID 32 Strep.

Positive results for alpha-arabinosidase, L-arginine arylamidase, acid production from: fructose & glucose.

Negative results for arginine dihydrolase, catalase, citrate utilization, esculin hydrolysis, alpha-fucosidase, gelatin hydrolysis,
alpha-galactosidase, alpha- and beta-glucosidase, beta-glucuronidase, N-acetyl-beta-glucosaminidase, indole production,  nitrates
reduction, oxidase, phenylalanine arylamidase, proline arylamidase, pyrrolidonyl arylamidase, urease, acid production from:
L-arabinose, D-cellobiose, glycerin, lactose, maltose, mannitol, D-melezitose, D-raffinose, D-rhamnose, salicin, D-sorbitol, sucrose,
D-trehalose & D-xylose. Glucose and fructose are the only sugars usually fermented. Does not coagulate milk.

Variable results for beta-galactosidase, phosphatase & acid production from mannose.
Some strains metabolize sucrose, melezitose, maltose, and salicin.
(c) Costin Stoica
Culture media
Biochemical tests
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