Pichia
Two species previously classified in the genus Candida have now been transferred to the genus Pichia. Pichia kudriavzevii (formerly Candida krusei) and Pichia norvegensis (formerly Candida norvegensis).
Species descriptions
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Pichia kudriavzevii
Synonymy:
Candida krusei, Issatchenkia orientalis.Pichia kudriavzevii is regularly associated with some forms of infant diarrhoea and occasionally with systemic disease. It has also been reported to colonise the gastrointestinal, respiratory and urinary tracts of patients with granulocytopenia. Environmental isolations have been made from beer, milk products, skin, faeces of animals and birds.
RG-2 organism.
Culture:
Colonies (SDA) white to cream-coloured smooth, glabrous, yeast-like.Microscopy:
Predominantly small, elongated to ovoid blastoconidia, 2-5 x 4-5 µm.India ink preparation:
Negative - no capsules present.Dalmau plate culture:
Abundant long, wavy, branched pseudohyphae with elongated to ovoid blastoconidia, budding off in verticillate branches.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 - 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 - Raffinose - Erythritol - Nitrate - Assimilation Melezitose - Ribitol - Urease - Glucose + Soluble Starch - Galactitol - 0.1% Cycloheximide v Galactose - D-Xylose - D-Mannitol - Growth at 40C + Key features:
Germ tube negative yeast and sugar assimilation pattern. Colonies pale pink on Candida CHROMagar.Antifungal susceptibility: Pichia kudriavzevii (Australian national data); MIC µg/mL. Note: Pichia kudriavzevii is intrinsically resistant to fluconazole.
Antifungal No ≤0.03 0.06 0.125 0.25 0.5 1 2 4 8 16 32 ≥64 AMB 308 1 2 25 47 91 100 40 2 FLU 353 2 27 147 177 ISAV 112 3 18 37 40 14 VORI 336 5 36 161 105 20 6 2 1 POSA 316 1 9 42 139 110 12 1 2 ITRA 308 2 3 35 150 102 14 2 ANID 287 103 122 60 2 MICA 287 3 73 188 23 5FC 308 1 3 3 6 29 175 85 5 1 -
Pichia norvegensis
Synonymy:
Candida norvegensis.Pichia norvegensis is a very rare clinical isolate that has been reported as a causative agent of peritonitis and disseminated candidiasis in a patient on CAPD.
RG-1 organism.
Culture:
Colonies (SDA) white to cream-coloured smooth, glabrous, yeast-like.Microscopy:
Ovoid to ellipsoid, budding blastoconidia, 2.0-4 x 3-10 µm.India ink preparation:
Negative - no capsules present.Dalmau plate culture:
Spherical to ovoid budding yeast cells only. Abundant pseudohyphae produced.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 - L-Arabinose - D-Glucitol - Fermentation Sucrose - D-Arabinose - 𝝰-M-D-Glucoside - Glucose s Maltose - D-Ribose - D-Gluconate - Galactose - Cellobiose + L-Rhamnose - DL-Lactate w Sucrose - Trehalose - D-Glucosamime + myo-Inositol - Maltose - Lactose - N-A-D-glucosamine - 2-K-D-Gluconate - Lactose - Melibiose - Glycerol + D-Glucuronate - Trehalose - Raffinose - Erythritol - Nitrate - Assimilation Melezitose - Ribitol - Urease - Glucose + Soluble Starch - Galactitol - 0.1% Cycloheximide - Galactose - D-Xylose - D-Mannitol - Growth at 37C + Key features:
Germ tube negative yeast and sugar assimilation pattern.Antifungal susceptibility: Pichia norvegensis very limited data (Australian national data); MIC µg/mL.
Antifungal No ≤0.03 0.06 0.125 0.25 0.5 1 2 4 8 16 32 ≥64 AMB 5 1 2 1 1 FLU 5 1 4 ISAV 1 1 VORI 4 1 2 1 POSA 4 1 3 ITRA 5 1 2 2 ANID 3 2 1 MICA 3 1 1 1 5FC 5 1 1 2 1