Characterization of clinical isolates of the Cryptococcus neoformans-Cryptococcus gattii species complex from the Amazonas State in Brazil

Abstract

Background: The differentiation and classification of pathogenic Cryptococcus species provides useful data for epidemiological studies and for the clinical diagnosis and treatment of patients.

Aims: The aim of this study was to characterise 40 clinical Cryptococcus isolates obtained from patients at the Tropical Medicine Foundation of Amazonas (FMTAM) from 2006 to 2008.

Methods: It was used phenotypic (i.e., enzyme production and antifungal resistance) and molecular biological (URA5-RFLP) experiments.

Results: Patients with HIV/AIDS were most affected with cryptococcosis. Thirty-one (75.5%) of the clinical isolates were classified as Cryptococcus neoformans and 9 (22.5%) as Cryptococcus gattii. High amounts of protease and phospholipase enzymes were produced by most of the isolates. Using the disk diffusion test (CLSI M44-A), 81, 35 and 100% of the C. neoformans isolates were characterized as susceptible to fluconazole, itraconazole and amphotericin B, respectively, whereas 78, 56 and 100% of the C. gattii isolates were susceptible to these antimicrobial agents. The average of Minimal Inhibitory Concentration (MIC) for C. neoformans and C. gattii isolates was 0.26 and 0.58 μg/mL, respectively. The 9 isolates of C. gattii had a fingerprint pattern comparable with the VGII molecular type, while all 31 isolates of C. neoformans presented with a pattern consistent with the VNI type.

Conclusions: This study confirms the importance of HIV/AIDS for the cryptococcosis epidemiology, the susceptibility of the isolates to amphotericin B and the high prevalence of the molecular genotypes VNI and VGII in the north of Brazil.