Magnusiomyces
The name of this genus has changed several times in recent years because of changes in nomenclatural rules (de Hoog et al., 2020). Based on a phylogenetic analysis of rDNA gene sequences, de Hoog and Smith (2004) transferred Geotrichum capitatum to the genus Magnusiomyces and Geotrichum clavatum to Saprochaete clavata. More recently Kaplan et al. (2018, 2021) using multilocus sequence typing of various genes, such as RPB2 have re-defined Saprochaete clavata as Magnusiomyces clavatus.
Magnusiomyces capitatus and M. clavatus are human pathogens that are closely related and are frequently mistaken for each other. Based on ITS sequences, Desnos-Ollivier et al. (2014) proposed species-specific carbon assimilation patterns and MALDI-TOF MS fingerprints to enable the identification of M. capitatus, M. clavatus, and Dipodascus geotrichum (Geotrichum candidum) to the species level.
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Magnusiomyces capitatus
Synonymy:
Saprochaete capitata (Diddens & Lodder) de Hoog & M.Th. Smith Geotrichum capitatum (Diddens & Lodder) v. Arx; Trichosporon capitatum Diddens & Lodder; Blastoschizomyces capitis (Diddens & Lodder) Salkin et al.Magnusiomyces capitatus occurs quite commonly in humans, usually as a transient component of normal skin flora and sputum. Systemic infections including pulmonary, fungaemia and endocarditis have been reported in immunosuppressed patients.
RG-1 organism.
Morphological description:
Colonies are moderately fast growing, flat, whitish, and finely suede-like with no reverse pigment. Hyphae are profusely branched at acute angles, with terminal and intercalary conidiogenous cells which form long, cicatrised rachids on which conidia are borne. Conidia are hyaline, smooth, one-celled, cylindrical to clavate, with a rounded apex and flat base, 7-10 x 2.5-3.5 μm. Rectangular arthroconidia are also often present.Molecular identification:
ITS sequencing recommended (de Hoog and Smith 2004).Note: Magnusiomyces capitatus and Magnusiomyces clavatus are human pathogens that are closely related and are frequently mistaken for each other. Based on ITS sequences, Desnos-Ollivier et al. (2014) proposed species-specific carbon assimilation patterns and MALDI-TOF MS fingerprints to enable the identification of M. clavatus, M. capitatus and Geotrichum candidum (Galactomyces candidus) to the species level.
Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data Germ Tube - L-Sorbose v L-Arabinose - D-Glucitol + Fermentation Sucrose - D-Arabinose - 𝝰-M-D-glucoside - Glucose - Maltose - D-Ribose - D-Gluconate - Galactose - Cellobiose - L-Rhamnose - DL-Lactate + Sucrose - Trehalose - D-Glucosamine - myo-Inositol - Maltose - Lactose - NAD-glucosamine nd 2-K-D-Gluconate - Lactose - Melibiose - Glycerol + D-Glucuronate nd Trehalose - Raffinose - Erythritol - Nitrate - Assimilation Melezitose - Ribitol - Urease - Glucose + Soluble Starch - Galactitol - 0.1% Cycloheximide + Galactose + D-Xylose - D-Mannitol + Growth at 40C + Antifungal susceptibility: Magnusiomyces capitatus limited data (Garcia-Ruiz et al. 2013, Australian national data); MIC μg/mL. Note: Isolates of M. capitatus are intrinsically resistant to echinocandins (Arendrup et al. 2015).
No ≤0.03 0.06 0.125 0.25 0.5 1 2 4 8 16 32 ≥64 AmB 11 1 1 5 4 FLU 11 2 2 2 3 2 VORI 10 2 3 2 1 1 1 POSA 10 2 1 3 2 2 ITRA 11 2 4 5 5FC 6 4 1 1 -
Magnusiomyces clavatus
Synonymy:
Saprochaete clavata, Geotrichum clavatum.Magnusiomyces clavatus (formerly known as Geotrichum clavatum or Saprochaete clavata) has only very infrequently been described as involved in invasive human infection. However, an outbreak of invasive infections caused by Magnusiomyces clavatus in haematology patients has been reported (Vaux et al. 2013).
RG-1 organism.
Morphological description:
Colonies are moderately fast growing, flat, whitish and butyrous. True hyphae are abundant, soon breaking up into rectangular arthroconidia of variable size, 2.8-4 3 x 6-20 μm. Sympodial conidiogenesis is occasionally present. Terminal parts of hyphae may swell and become thick-walled.Note: Magnusiomyces clavatus and Magnusiomyces capitatus are human pathogens that are closely related and are frequently mistaken for each other.
Molecular identification:
ITS sequencing is recommended for accurate species identification.MALDI-TOF MS:
Reliably identifies M. clavatus, M. capitatus and Geotrichum candidum to the species level (Desnos-Ollivier et al. 2014).Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data Germ Tube - L-Sorbose + L-Arabinose - D-Glucitol - Fermentation Sucrose - D-Arabinose - 𝝰-M-D-glucoside - Glucose - Maltose - D-Ribose - D-Gluconate - Galactose - Cellobiose + L-Rhamnose - DL-Lactate +,w Sucrose - Trehalose - D-Glucosamine - myo-Inositol - Maltose - Lactose - NAD-glucosamine nd 2-K-D-Gluconate - Lactose - Melibiose - Glycerol + D-Glucuronate nd Trehalose - Raffinose - Erythritol - Nitrate - Assimilation Melezitose - Ribitol - Urease - Glucose + Soluble Starch - Galactitol - 0.1% Cycloheximide - Galactose + D-Xylose - D-Mannitol - Growth at 40C + Antifungal susceptibility: Magnusiomyces clavatus (Geotrichum clavatum, Saprochaete clavata) very limited data (1); MIC µg/mL.
Note: M. clavatus reported to be intrinsically resistant to echinocandins.No ≤0.016 0.03 0.06 0.125 0.25 0.5 1 2 4 ≥8 AmB 4 1 1 1 1 VORI 3 1 1 1 POSA 3 2 1 ITRA 4 2 2 5FC 4 2 1 1
References
- Arendrup, M.C., Boekhout, T., Akova, M., et al. (2014) ESCMID and ECMM joint clinical guidelines for the diagnosis and management of rare invasive yeast infections. Clinical Microbiology and Infection, 20, Suppl 3, 76-98.
- de Hoog, G.S. and Smith, M.T. (2004) Ribosomal gene phylogeny and species delimitation in Geotrichum and its teleomorphs. Studies in Mycology, 50, 489-515.
- de Hoog, G.S. and Smith, M.T. (2011) Chapter 97, Saprochaete Coker & Shanor ex D.T.S. Wagner & Dawes (1970), in Kurtzman, C.P., Fell, J.W. and Boekhout, T. (eds), The Yeasts, a Taxonomic Study, 5th edition, Elsevier B.V., pp. 1317-1327.
- de Hoog, G.S. and Smith, M.T. (2011) Chapter 45, Magnusiomyces Zender (1977), in Kurtzman, C.P., Fell, J.W. and Boekhout, T. (eds), The Yeasts, a Taxonomic Study, 5th edition, Elsevier B.V., pp. 565-574.
- de Hoog, G.S., Guarro, J., J. Gene, J., et al. (2020) Atlas of clinical fungi. 4th edition. Foundation Atlas of Clinical Fungi https://webshop.atlasclinicalfungi.org.
- Desnos-Ollivier, M., Blanc, C., Garcia-Hermoso, D., et al. (2014) Misidentification of Saprochaete clavata as Magnusiomyces capitatus in clinical isolates: utility of internal transcribed spacer sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry and importance of reliable databases. Journal of Clinical Microbiology, 52, 2196-2198.
- Garcia-Ruiz, J.C., Lopez-Soria, L., Olazabal, I., et al. (2013) Invasive infections caused by Saprochaete capitata in patients with haematological malignancies: report of five cases and review of the antifungal therapy. Revista Iberoamericana Micologia, 30, 248-255.
- Kaplan, E., Al-Hatmi, A.M.S., Ilkit, M., et al. (2018) Molecular diagnostics of arthroconidial yeasts, frequent pulmonary opportunists. Journal of Clinical Microbiology, 56, e01427-17.
- Kaplan, E., Aktaş, D., Dogen, A., et al. (2021) Development and analysis of qPCR for the identification of arthroconidial yeasts of the genus Magnusiomyces. Mycopathologia, 186, 41-51.
- Noster, J., Koeppel, M. B., Desnos-Olivier, M., et al. (2022) Bloodstream infections caused by Magnusiomyces capitatus and Magnusiomyces clavatus: Epidemiological, clinical, and microbiological features of two emerging yeast species. Antimicrobial Agents and Chemotherapy, 66, e0183421.
- Vaux, S., Criscuolo, A., Desnos-Ollivier, M., et al. (2014) Multicenter outbreak of infections by Saprochaete clavata, an unrecognized opportunistic fungal pathogen. mBio, 5, e02309-14.