The brown colour effect (BCE) of Cryptococcus neoformans in the diagnosis, control and epidemiology of C. neoformans infections in AIDS patients

Staib, F.; Seibold, Michael; Antweiler, E.; Fröhlich, B.; Weber, Sarah; Blisse, A

doi:10.1016/s0176-6724(87)80030-5

Cited by 50 publications

(58 citation statements)

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“…Although many pathogenic fungi synthesize precursors of melanin, melanization in C. neoformans occurs when exogenous or environmental catechols or aminophenols are oxidatively polymerized by the laccase enzyme and deposited as melanin in the cell wall (1,26). Melanization has often been used for the identification of isolates, since growth of brown colonies on birdseed agar made from Guizotia abyssinica, or thistle seeds rich in caffeic acid, is characteristic of C. neoformans (29). However, we noted that several strains of species other than C. neoformans produced light-brown colonies on this medium or on defined medium containing synthetic substrates.…”

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confidence: 66%

Laccase and Melanization in Clinically Important Cryptococcus Species Other than Cryptococcus neoformans

et al. 2002

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The laccase enzyme and melanin synthesis have been implicated as contributors to virulence in Cryptococcus neoformans. Since isolations of Cryptococcus species other than C. neoformans from clinical specimens have been increasing, we examined the laccase activities of C. albidus, C. laurentii, C. curvatus, and C. humicola. Incubation of cells with epinephrine produced adrenochrome color in C. albidus, C. laurentii, and C. curvatus but not in C. humicola. Activity was always less than in C. neoformans. Laccase was detected in the soluble fractions of disrupted C. albidus, C. laurentii, and C. curvatus cells. Activity staining of partially purified enzyme after nondenaturing polyacrylamide gel electrophoresis revealed that laccases from C. albidus, C. laurentii, and C. curvatus migrated more slowly than that from C. neoformans. One strain of C. curvatus exhibited two melanin bands. Thus, several clinically emerging Cryptococcus species express laccase and can synthesize melanin.Cryptococcosis is a life-threatening infection that complicates a variety of immunocompromising conditions (4). Although 34 species of the genus Cryptococcus are recognized (6), C. neoformans is generally considered to be the pathogenic species, while C. albidus, C. laurentii, and C. curvatus have been regarded as saprophytic species. However, species other than C. neoformans have, in fact, been isolated from normally sterile clinical specimens. We note isolations of C. albidus in septicemia and meningitis (15,22,23), C. laurentii in fungemia (14,19) and meningitis (15), C. curvatus in myeloradiculitis (5), and C. humicola in meningitis (28), all in patients with AIDS or cancer. Thus, cryptococcosis due to species other than C. neoformans may be considered an emerging infection.The virulence of C. neoformans has been ascribed to capsule formation, melanization due to laccase (phenoloxidase), proteinase secretion, and phospholipases (3). Although many pathogenic fungi synthesize precursors of melanin, melanization in C. neoformans occurs when exogenous or environmental catechols or aminophenols are oxidatively polymerized by the laccase enzyme and deposited as melanin in the cell wall (1, 26). Melanization has often been used for the identification of isolates, since growth of brown colonies on birdseed agar made from Guizotia abyssinica, or thistle seeds rich in caffeic acid, is characteristic of C. neoformans (29). However, we noted that several strains of species other than C. neoformans produced light-brown colonies on this medium or on defined medium containing synthetic substrates. In this study, we examined laccase enzymes and melanization in cryptococcal species other than C. neoformans. MATERIALS AND METHODSStrains used. The strains used in this study are listed in Table 1 as accessed in the culture collections Centraalbureau voor Schimmelcultures (CBS) and Japan Collection of Microorganisms (JCM). The strains were obtained from each institute directly and maintained on YM agar (Difco) slants. Some of the strains have recently been ...

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confidence: 66%

Laccase and Melanization in Clinically Important Cryptococcus Species Other than Cryptococcus neoformans

et al. 2002

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“…Fifteen ml of the filtrate were mixed with 50 µl of a solution of penicillin (20 U) and streptomycin (40 U) and 100 µl of this suspension was plated in Guizotia abyssinica agar, supplemented with penicillin and streptomycin (20). Plates were incubated at 27 °C for one month, with weekly observation.…”

Section: Sample Processingmentioning

confidence: 99%

Primer aislamiento ambiental de Cryptococcus gattii de serotipo B, en Cúcuta, Colombia

Firacative

Torres

Rodríguez³

et al. 2011

biomedica

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Introduction. In Cúcuta, Cryptococcus gattii serotype B is commonly recovered from immunocompetent patients with cryptococcosis, but it has not been recovered from the environment in spite of its high incidence which is 77% out of reported cases. Objective. The aim of this work was to carry out an extensive environmental sampling in Cúcuta, in an attempt to isolate C. gattii serotype B and to expand our knowledge about the ecology and epidemiology of this important yeast. Materials and methods. Samples associated with 3,634 trees from 40 zones of Cúcuta were collected and processed with 28 samples collected near the houses of four patients with cryptococcosis caused by C. gattii serotype B. The serotype of the recovered isolates was done using multiplex PCR, molecular patterns were determined by RFLP of the URA5 gene and mating type was determined using the primers MfαU, MfαL, MFa2U and MFa2L. Results. In total, 4,389 samples were processed and one isolate of C. gattii serotype B (VGI/a), two isolates of C. gattii serotype C (VGIII/α) and three isolates of C. neoformans var. grubii, serotype A (VNI/α), were recovered. The density of the recovered isolates varied from 50 to 350 cfu/g of soil.Conclusions. This is the first report on the environmental isolation of C. gattii serotype B from Cúcuta. However, because of the low rate of recovery of isolates from soil only, the environmental niche of C. gattii has not been established and further environmental studies in Cúcuta are necessary, owing that this serotype is not only causing cryptococcosis but also has shown a higher virulence after the Vancouver outbreak.

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“…The formation of brown pigment due to phenol oxidase activity on medium containing seed extracts of Guizotia abyssinica (Staib's niger seed agar) or Helianthus annus (Pal's sunflower seed agar) or on medium containing chemicals such as caffeic acid or L-3,4-dihydroxyphenylalanine (L-DOPA) has been widely used as a criterion for the identification of this fungus (1,3). In a search for a simple alternative seed-based medium for identification of C. neoformans, mustard seed extracts were found to induce the brown color effect (BCE) in C. neoformans.…”

Section: Mustard Seed Agar a New Medium For Differentiation Of Cryptmentioning

confidence: 99%

Mustard Seed Agar, a New Medium for Differentiation of Cryptococcus neoformans

et al. 2006

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The brown colour effect (BCE) of Cryptococcus neoformans in the diagnosis, control and epidemiology of C. neoformans infections in AIDS patients

Cited by 50 publications

References 15 publications

Laccase and Melanization in Clinically Important Cryptococcus Species Other than Cryptococcus neoformans

Laccase and Melanization in Clinically Important Cryptococcus Species Other than Cryptococcus neoformans

Primer aislamiento ambiental de Cryptococcus gattii de serotipo B, en Cúcuta, Colombia

Mustard Seed Agar, a New Medium for Differentiation of Cryptococcus neoformans

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