[Pigmentation of Cryptococcus neoformans strains on sunflower seed agar]. / Pigmentación de cepas de Cryptococcus neoformans sobre agar semilla de girasol.

The production of melanin on a medium of sunflower seeds extract agar from 86 strains of Cryptococcus neoformans belonging to the Mycology Laboratory of "Pedro Kouri" Institute of Tropical Medicine was determined. 54.7% of them produced colonies with dark brown pigment, 5.8% a light pigment and 37.2% an intermediate tonality. A fourth group was created for those strains with a true pigment (2.3%). This paper is an important contribution to attain a better characterization of the strains from the collection of the institution and serves as a basis to further studies of pathogenicity and susceptibility.

Sensibilidad de aislamientos clínicos de Candida albicans frente a la 5-fluorocitosina / Sensitivity of clinical isolates of Candida albicans to 5-fluorocytosine

5-fluorocytosine has been one of the most used antimycotics in the therapeutics of mycosis, however the appearance of resistant strains may be an important limitant for its use. That's why it is necessary to know the sensitivity to this drug. To this end, it was determined the minimum inhibitory concentration (MIC) of 5-fluorocytosine against 50 clinical isolates of Candida albicans by a micromethod of dilution in RPMI 1640 media, comparing 2 reading methods. The values of the geometrical mean obtained were 0.95 mg/mL for the visual reading and 0.75 mg/mL for the automated reading. There were no significant differences between them (p < 0.05). Pearson's lineal correlation coefficient was r = 0.81. It indicates that although there was a good correlation, there was also discrepancy between both readings. The IMC50 was of 0.5 microgram/mL and the IMC90 of 4 mg/mL. 90 and 92 of sensitive strains, between 6 and 8 of resistant strains and 2 of strains with intermediate sensitivity were found depending on the reading method used. These values show a low resistance against this drug, which may have a direct repercussion on the therapeutic behaviour to be followed in candidiasis.

Determinación de la concentración mínima inhibitoria de fluconazol frente a Cryptococcus neoformans / Determination of the minimum inhibitory concentration of fluconazole against Cryptococcus neoformans

The minimum inhibitory concentration of fluconozole was determined in 36 strains of Cryptococcus neoformans var. neoformans by a casitone broth microdilution method, taking into account that it is one of the most used antifungal agents in our country for the treatment of cryptococcal meningitis, the second opportunistic mycosis in order of frequency and that with the highest lethality among AIDS patients. The minimum inhibitory concentration of the studied strains ranged 0.125 to more than 64 micrograms/mL for a geometrical mean of 2.38 micrograms/mL. 50 of the strains were inhibited with 4 micrograms/mL and the least concentration that inhibited 90 was 16 micrograms/mL. It is stressed the importance of continuing this type of in vitro studies to detect the appearance of resistance of C. neoformans to antifungal agents.