Candida orthopsilosis

Candida orthopsilosis is recognised as part of the Candida parapsilosis species complex (Tavanti et al., 2005).

It is phenotypically indistinguishable from C. parapsilosis, C. metapsilosis and Lodderomyces elongisporus and is best identified by ITS sequencing or MALDI-ToF MS.

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	≤0.016	0.03	0.06	0.125	0.25	0.5	1	2	4	8	16	≥64
AMB	224		3	3	30	46	61	49	23	9
FLU	199				1	9	47	86	24	16	9	4	3
ISAV	3	1	1	1
VORI	179	70	51	36	6	13	2	2
POSA	139	5	22	50	42	9	11
ITRA	97	3	14	32	32	16
ANID	89		1		3	9	20	46	10
MICA	88	1	1		3	37	39	6	1
5FC	95			58	22	9	3	1		1			1

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