Madurella mycetomatis

The genus Madurella was originally based on tissue morphology (mycetoma with black grains) and the formation of sterile cultures on mycological media.

Initially two species were described, M. mycetomatis and M. grisea. However recent molecular studies have recognised five species: Madurella mycetomatis, Trematosphaeria grisea (formerly M. grisea), M. fahalii, M. pseudomycetomatis and M. tropicana (Desnos-Ollivier et al. 2006, de Hoog et al. 2004a, 2012). All species have been isolated from soil and are major causative agents of mycetoma.

RG-2 organism.

Culture showing the typical brown diffusable pigment in the agar and phialides of M. mycetomatis

Culture showing the typical brown diffusable pigment in the agar and phialides of M. mycetomatis (rarely seen as most isolates are sterile).

Morphological description: 
Colonies are slow growing, flat and leathery at first, white to yellow to yellowish-brown, becoming brownish, folded and heaped with age, and with the formation of aerial mycelia. A brown diffusible pigment is characteristically produced in primary cultures. Although most cultures are sterile, two types of conidiation have been observed, the first being flask-shaped phialides that bear rounded conidia, the second being simple or branched conidiophores bearing pyriform conidia (3-5 µm) with truncated bases. The optimum temperature for growth of this mould is 37C.

Grains of Madurella mycetomatis (tissue microcolonies) are brown or black, 0.5-1.0 mm in size, round or lobed, hard and brittle, composed of hyphae which are 2-5 µm in diameter, with terminal cells expanded to 12-15 (30) µm in diameter.

M. mycetomatis can be distinguished from Trematosphaeria grisea by growth at 37C and its inability to assimilate sucrose.

Key features: 
Black grain mycetoma, growth at 37C, diffusible brown pigment produced on culture and the occasional presence of phialides.

Molecular identification: 
ITS sequencing is recommended for species separation (Ahmed et al. 2014b, Desnos-Olliver et al. 2006, Irinyi et al. 2015). A five locus phylogenetic analysis was performed by Ahmed et al. (2014a) using the ITS, D1/D2, RPB2 and EF-1α genes.

References: 

  • Ahmed, S.A., van den Ende, G., Fahal, B., et al. (2014a) Rapid identification of black grain eumycetoma causative agents using Rolling Circle Amplification. PLoS Neglected Tropical Diseases, 8, e3368-e3368.
  • Ahmed, S.A., van de Sande, W.W.J., Stevens, D.A., et al. (2014b) Revision of agents of black-grain eumycetoma in the order Pleosporales. Persoonia, 33, 141-154.
  • Ahmed, E.A., Nour, B.Y.M., Abakar, A.D., (2020) The genus Madurella: Molecular identification and epidemiology in Sudan. PLoS Neglected Tropical Diseases, 14(7), e0008420-e0008420.
  • Chandler, F.W., Kaplan, W.and Ajello, L. (1980) A colour atlas and textbook of the histopathology of mycotic diseases. Wolfe Medical, London.
  • de Hoog, G.S., Adelmann, D., Ahmed, A.O.A., et al. (2004a) Phylogeny and typification of Madurella mycetomatis, with a comparison of other agents of eumycetoma. Mycoses, 47, 121-130.
  • de Hoog, G.S., van Diepeningen, A.D., Mahgoub, el-S., et al. (2012) New species of Madurella, causative agents of black-grain mycetoma. Journal of Clinical Microbiology, 50, 988-994.
  • de Hoog, G.S., Guarro, J., Gene, J., et al. (2015) Atlas of Clinical Fungi (Version 4.1.2). Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands.
  • Desnos-Ollivier, M., Bretagne, S., Dromer, F., et al. (2006) Molecular identification of black-grain mycetoma agents. Journal of Clinical Microbiology, 44, 3517-3523.
  • Irinyi, L., Serena, C., Garcia-Hermoso, D., et al. (2015) International Society of Human and Animal Mycology (ISHAM)-ITS reference DNA barcoding database-the quality controlled standard tool for routine identification of human and animal pathogenic fungi. Medical Mycology, 53, 313-337.
  • Kidd, S., Halliday, C., Ellis, D. (2023) Descriptions of Medical Fungi (4th edition). CABI.
  • McGinnis, M.R. (1980) Laboratory handbook of medical mycology. Academic Press, New York.
  • Rippon, J.W. (1988) Medical mycology: the pathogenic fungi and the pathogenic actinomycetes, 3rd edition. W,B. Saunders Co, Philadelphia, USA.
  • Yan, J., Deng, J., Zhou, C.J., et al. (2010) Phenotypic and molecular characterization of Madurella pseudomycetomatis sp. nov., a novel opportunistic fungus possibly causing black-grain mycetoma. Journal of Clinical Microbiology, 48, 251-257.

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