Kluyveromyces marxianus

Synonymy: 
Candida kefir, Candida pseudotropicalis.

Kluyveromyces marxianus is a rare cause of candidiasis and is usually associated with superficial cutaneous manifestations rather than systemic disease.

Environmental isolations have been made from cheese and dairy products.

RG-1 organism.

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

Microscopy: 
Short-ovoid to long-ovoid, budding blastoconidia, 3.0-6.5 x 5.5-11.0 µm, sometimes becoming elongate (up to 16.0 µm).

India ink preparation: 
Negative - no capsules present.

Dalmau plate culture: 
Abundant, long, wavy, branched pseudohyphae usually formed, with ovoid blastoconidia, budding off singly, in pairs or chains, often in a verticillated position. Note: In some strains pseudohyphae may be scarce or almost absent.

Molecular identification: 
ITS sequencing recommended.

MALDI-TOF MS: 
Able to accurately identify this species.

Physiological Tests: + Positive, - Negative, v Variable, w Weak, s Slow, nd No Data
Germ Tube - L-Sorbose v L-Arabinose v D-Glucitol v
Fermentation   Sucrose + D-Arabinose - 𝝰-M-D-Glucoside -
Glucose + Maltose - D-Ribose v D-Gluconate -
Galactose +,s Cellobiose v L-Rhamnose - DL-Lactate +
Sucrose + Trehalose -,w D-Glucosamime - myo-Inositol -
Maltose - Lactose v N-A-D-glucosamine - 2-K-D-Gluconate -
Lactose v Melibiose - Glycerol s D-Glucuronate nd
Trehalose - Raffinose + Erythritol - Nitrate -
Assimilation   Melezitose - Ribitol s Urease -
Glucose + Soluble Starch - Galactitol - 0.1% Cycloheximide +
Galactose s D-Xylose s D-Mannitol v Growth at 40C +

Key features: 
Germ tube negative yeast and sugar assimilation pattern.

Antifungal susceptibility: Kluyveromyces marxians (Diekema et al. 2009, Pfaller et al. 2013 and 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 95       6 28 50 10         1   1
FLU 111   1 22 62 19 6 1              
ISAV 13 4 8 1                      
VORI 111 109 2                        
POSA 106 30 33 31 10 2                  
ITRA 37 11 12 12 12 2                  
ANID 86 15 37 29 4                    
MICA 71 33 42 4 1 1                  
CAS 106 95 5 3 2 1                  
5FC 21 4 8     2   1 1 3 1        

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