Rhodotorula rubra

Synonym: Rhodotorula mucilaginosa

On Sabouraud's dextrose agar cultures are coral pink, usually smooth, sometimes reticulate, rugose or corrugated, moist to mucoid yeast-like in appearance. Microscopic morphology shows spherical to elongate budding yeast-like cells or blastoconidia, 2.5-6.5 x 6.5-14.0 um in size.

India Ink Preparation: Small capsules present.

Dalmau Plate Culture on Cornmeal And Tween 80 Agar: Budding blastoconidia only. No pseudohyphae are formed.

Physiological Tests:

Germ Tube test is Negative
Hydrolysis of Urea is Positive
Growth on Cycloheximide medium is Negative
Growth at 37C is Variable

Fermentation Reactions: Where fermentation means the production of gas and is independent of pH changes.

Negative: Glucose; Sucrose; Lactose; Galactose; Maltose; Trehalose.

Assimilation Tests:

Positive: Glucose; Sucrose; Trehalose; D-Xylose; Raffinose; D-Arabinose (delayed); Ribitol (some negative).
Variable: Galactose; Melezitose; Maltose; Glycerol; Succinic acid; Cellobiose; L-Rhamnose; L-Arabinose; DL-Lactic acid; L-Sorbose; D-Ribose; Galactitol; D-Mannitol; D-Glucitol; Salicin; Citric acid.
Negative: Potassium nitrate; Lactose; Melibiose; Erythritol; Inositol; Soluble Starch.

Rhodotorula rubra includes the nitrate negative strains of Rhodotorula which assimilate maltose, sucrose, melezitose and raffinose but not lactose.

Clinical significance:

Rhodotorula rubra is a common airborne contaminant of skin, lungs, urine and faeces. R. rubra is a known cause of fungal peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). This is usually due to saprophytic colonization of catheters or dialysis machinery and removal of the source of contamination usually leads to clearing of the symptoms. It has also been reported as causing fungemia, endocarditis and meningitis in patients undergoing chemotherapy for cancer and those with indwelling intravenous catheters.

Mycosis: Miscellaneous Yeast Infections

Further reading:

Kreger-Van Rij, N.J.W. (ed) 1984. The Yeasts: a taxonomic study. 3rd Edition. Elsevier Science Publishers B.V., Amsterdam, The Netherlands.

Rippon, J.W. 1988. Medical Mycology. 3rd Edition. W.B. Saunders Co., Philadelphia, USA