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 Saprochaeta clavata. More recently Kaplan et al. (2018, 2021) using multilocus sequence typing of various genes, such as RPB2 have re-defined Saprochaeta 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.

  • 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 Saprochaete clavata 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 S. clavata, 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 +

    References: de Hoog and Smith (2004, 2011c), de Hoog et al. (2015), Garcia-Ruiz et al. (2013), Desnos-Ollivier et al. (2014), Arendrup et al. (2015).

    Antifungal susceptibility: Magnusiomyces capitatus limited data (Garcia-Ruiz et al. 2013, Australian national data); MIC μg/mL. Note: Isolates of M. capitatis 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 9     1 1 4 3            
    FLU 9             1 1 2 3 2  
    VORI 8 2 2 2 1   1            
    POSA 8   2 1 2 2 1            
    ITRA 9     1 4 4              
    5FC 4   2 1   1              


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  • Magnusiomyces clavatus

    Synonmy: 
    Saprochaeta clavata, Geotrichum clavatum.

    Saprochaete clavata (formerly known as Geotrichum clavatum or Saprochaeta clavata,) has only very infrequently been described as involved in invasive human infection. However, an outbreak of invasive infections caused by Saprochaete clavata 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: Saprochaete clavata 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 S. clavata, M. capitatus and Geotrichum candidum to the species level (Desnos-Ollivier et al. 2014).

    References: 
    de Hoog and Smith (2004, 2011b), de Hoog et al. (2015), Desnos-Ollivier et al. (2014), Vaux et al. (2013), Arendrup 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: Saprochaete clavata (Geotrichum clavatum) very limited data (1); MIC µg/mL.  
    Note: S. claveta 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        


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