Cryptococcus neoformans - Doctor Fungus

(Sanfelice) Vuillemin (1901)

Macroscopic morphology

Colonies on Sabouraud dextrose agar at 25°C are cream to beige and mucoid due to the capsule surrounding the yeast cells. Some a-capsular strains have been recovered, particularly from HIV patients on long-term maintenance therapy. Colonies of such strains are white to cream and smooth similar in appearance to N/A(L):Candida spp. In contrast to other species, C. neoformans grows as a brown to black colony on agars containing caffeic acid such as Bird Seed Agar.

Microscopic morphology

On cornmeal following 72 hours incubation at 25°C, it produces globose yeast cells only (2.5-10 µm in diameter).

Special notes

This isolate is urease positive but fails to grow on medium containing cycloheximide or at 40°C. The type strain was isolated from peach juice. It was first described in human medicine in 1894 by Busse who observed the cells in a tumor from the tibia of a woman diagnosed with sarcoma [1270]. This species causes disease in both immunocompromised and immunocompetent host. Incidence increased dramatically with the onset of HIV but the leading risk factor for disease is impaired cell mediated immunity [181]. Serodiagnosis of this species breaks it out into one of 5 serotypes, A, B, C, D, and AD.
Cryptococcus neoformans var. neoformans (D), C. neoformans var. gattii (B, C), and C. neoformans var. grubii (A).
The validity of C. neoformans var. grubii is still being argued and some authors place serotype A as C. neoformans var. neoformans [1179] Serotype AD is still being characterized [1443]. This species responds well to the azoles but echinocandins are not typically indicated. Interestingly, high MICs to caspofungin are not due to the (1-3)beta-glucan synthase resistance but rather to another mechanism [1420].

FTL* in vitro susceptibility data

AMB	CAS	5FC	FLU	ITRA	VORI	KETO	POSA
0.06 µg/ml=2	4.0 µg/ml=1	&lt0.125 µg/ml=2	&lt0.125 µg/ml=5	&lt0.015 µg/ml=21	&lt0.015 µg/ml=23	&lt0.03 µg/ml=2	&lt0.015 µg/ml=4
0.125 µg/ml=28	8.0 µg/ml=3	0.25 µg/ml=4	0.25 µg/ml=5	0.03 µg/ml=27	0.03 µg/ml=36	0.06 µg/ml=7	0.03 µg/ml=4
0.25 µg/ml=137	16 µg/ml=26	0.5 µg/ml=8	0.5 µg/ml=20	0.06 µg/ml=22	0.06 µg/ml=33	0.125 µg/ml=9	0.06 µg/ml=4
0.5 µg/ml=41	&gt16 µg/ml=6	1.0 µg/ml=19	1.0 µg/ml=47	0.125 µg/ml=22	0.125 µg/ml=28	0.25 µg/ml=19	0.125 µg/ml=2
1.0 µg/ml=5		2.0 µg/ml=22	2.0 µg/ml=94	0.25 µg/ml=15	0.25 µg/ml=18
		4.0 µg/ml=46	4.0 µg/ml=45	0.5 µg/ml=1	0.5 µg/ml=7
		8.0 µg/ml=16	8.0 µg/ml=27
		&gt64 µg/ml=3	16 µg/ml=19
			32 µg/ml=9
			64 µg/ml=4

Drug/N	AMB/213	CAS/36	5FC/120	FLU/275	ITRA/108	VORI/145	KETO/27	POSA/14
MIC Range	0.06-0.5	4->16	<0.125->64	<0.125-64	<0.015-0.5	<0.015-0.5	<0.03-0.25	<0.015-0.5
MIC₅₀	0.25	16	8.0	2.0	0.06	0.06	0.25	0.03
MIC₉₀	0.5	>16	8.0	8	0.25	0.25	0.25	**

* Fungus Testing Laboratory unpublished data (CLSI M27-A2)

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