Candida orthopsilosis

RG-2 organism.

Culture: 
Colonies (SDA) white to cream-coloured smooth, glabrous, yeast-like.

Microscopy: 
Ellipsoid to subglobose budding blastoconidia, 2-5 x 3-7 µm, with some larger elongated forms present.

India ink preparation: 
Negative - no capsules present.

Dalmau plate culture:
Abundant, much-branched pseudohyphae produced.

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 -
Sucrose - Trehalose + D-Glucosamime - myo-Inositol -
Maltose - Lactose - N-A-D-glucosamine + 2-K-D-Gluconate +
Lactose - Melibiose - Glycerol + D-Glucuronate -
Trehalose -,s Raffinose - Erythritol - Nitrate -
Assimilation   Melezitose + Ribitol + Urease -
Glucose + Soluble Starch v Galactitol - 0.1% Cycloheximide -
Galactose + D-Xylose + D-Mannitol + Growth at 37C +

Key features:  
Candida orthopsilosis cannot be distinguished morphologically from C. parapsilosis and C. metapsilosis, but can be identified by ITS sequencing (Asadzadeh et al. 2009, Borman et al. 2009, Tavanti et al. 2005) and MALDI-TOF MS analysis.

Antifungal susceptibility: Candida orthopsilosis (Australian national data); MIC µg/mL.
Antifungal No ≤0.008 0.016 0.03 0.06 0.125 0.25 0.5 1 2 4 8 16 32 ≥64
AMB 224     3 3 30 45 60 48 23 9        
FLU 196         1 9 45 85 24 16 9 4   3
VORI 176 28 40 51 35 6 13 2 2            
POSA 136   5 21 49 41 9 11              
ITRA 94 1 2 14 30 32 15                
ANID 86     1   2 9 20 44 10          
MICA 85   1 1   3 36 37 6 1          
CAS 146 2     56 22 8 3 1   1       1
5FC                              

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