RESUMEN
Cryptococcus neoformans and Cryptococcus gattii are closely related pathogenic fungi. Cryptococcus neoformans is ecologically widespread and affects primarily immunocompromised patients, while C. gattii is traditionally found in tropical climates and has been reported to cause disease in immunocompetent patients. l-Canavanine glycine bromothymol blue (CGB) agar can be used to differentiate C. neoformans and C. gattii, but there are few reports of its performance in routine clinical practice. Growth of C. gattii on CGB agar produces a blue color, indicating the assimilation of glycine, while C. neoformans fails to cause a color change. Using reference and clinical strains, we evaluated the ability of CGB agar and D2 large ribosomal subunit DNA sequencing (D2 LSU) to differentiate C. neoformans and C. gattii. One hundred two yeast isolates were screened for urease activity, melanin production, and glycine assimilation on CGB agar as well as by D2 sequencing. Seventeen of 17 (100%) C. gattii isolates were CGB positive, and 54 of 54 C. neoformans isolates were CGB negative. Several yeast isolates other than the C. gattii isolates were CGB agar positive, indicating that CGB agar cannot be used alone for identification of C. gattii. D2 correctly identified and differentiated all C. gattii and C. neoformans isolates. This study demonstrates that the use of CGB agar, in conjunction with urea hydrolysis and Niger seed agar, or D2 LSU sequencing can be reliably used in the clinical laboratory to distinguish C. gattii from C. neoformans. We describe how CGB agar and D2 sequencing have been incorporated into the yeast identification algorithm in our laboratory.
Asunto(s)
Azul de Bromotimol , Canavanina , Criptococosis/diagnóstico , Cryptococcus gattii/aislamiento & purificación , Medios de Cultivo , Glicina , Análisis de Secuencia de ADN/métodos , Algoritmos , Azul de Bromotimol/metabolismo , Canavanina/metabolismo , Técnicas de Laboratorio Clínico/métodos , Cryptococcus gattii/genética , Cryptococcus gattii/crecimiento & desarrollo , Cryptococcus gattii/metabolismo , Cryptococcus neoformans/genética , Cryptococcus neoformans/crecimiento & desarrollo , Cryptococcus neoformans/aislamiento & purificación , Cryptococcus neoformans/metabolismo , Medios de Cultivo/química , ADN de Hongos/química , ADN de Hongos/genética , ADN Ribosómico/química , ADN Ribosómico/genética , Diagnóstico Diferencial , Proteínas Fúngicas/metabolismo , Glicina/metabolismo , Humanos , Melaninas/metabolismo , ARN Ribosómico 28S/genética , Ureasa/metabolismoRESUMEN
PathoTec strips and spot biochemical tests were evaluated for the ability to biotype Haemophilus influenzae and Haemophilus parainfluenzae. Indole, urease, and ornithine decarboxylase reactions were tested. The results of PathoTec strips compared favorably with those conventional methods; the percent agreements were as follows: indole, 100; urease, 99.5; and ornithine, 95.5. Spot tests were simple and rapid, and the results also compared favorably with those of conventional tests; the percent agreements were as follows: indole, 99; urease, 100; and ornithine, 96.