Epidemiological aspects of clinical and environmental Cryptococcus neoformans isolates in the Brazilian state Rio Grande do Sul.

Cryptococcus neoformans is a pathogenic fungus that causes life-threatening meningoencephalitis in immunocompromised patients (HIV-positive patients), and lymphoproliferative disorders in patients subjected to organ transplantation and other immunosuppressive therapies. This fungus is commonly found in soil and avian excreta, mainly from pigeon and turkey. We describe the isolation and characterization of 17 clinical and 10 environmental (pigeon excreta) isolates from the Brazilian state Rio Grande do Sul. We analyzed capsule formation, carbon assimilation pattern, canavanine-glycine-bromothymol blue (CGB) reaction, and nitrate and urease tests, as well as susceptibility to antifungal drugs. The genetic variability among C. neoformans isolates was studied using randomly amplified polymorphic DNA (RAPD) analysis. Eight of 22 arbitrary polymerase chain reaction primers used confirmed genetic polymorphism among the environmental isolates tested, suggesting that it remains feasible to use RAPD analysis as a typing method. Three of the selected primers yielded 10 molecular subclasses. The majority of the clinical isolates were assigned to the molecular subclass F. The RAPD data obtained reinforce the developing consensus about the population structure of this fungus.

In vitro susceptibility to antifungal agents of clinical and environmental Cryptococcus neoformans isolated in Southern of Brazil.

The purpose of the present study was to compare the susceptibility to four antifungal agents of 69 Cryptococcus neoformans strains isolated from AIDS patients with that of 13 C. neoformans strains isolated from the environment. Based on the NCCLS M27-A methodology the Minimal Inhibitory Concentrations (MICs) obtained for amphotericin B, itraconazole and ketoconazole were very similar for clinical and environmental isolates. Clinical isolates were less susceptible to fluconazole than environmental isolates. The significance of these findings and aspects concerning the importance, role and difficulties of C. neoformans susceptibility testing are also discussed.

Effects of three azole derivatives on the lipids of different strains of Sporothrix schenckii.

The comparative effects of ketoconazole, itraconazole, and fluconazole on the lipids of five Sporothrix schenckii strains were investigated. Quantitative analysis of lipids and sterols was completed, as well as qualitative analysis of sterols, by thin-layer chromatography and ultraviolet spectrophotometry. Growth of the S. schenckii isolates in the presence of azole derivative concentrations below the minimum inhibitory concentration (MIC) resulted in significant alterations in the lipid and sterol contents as compared with the control values. Furthermore, lanosterol was detected in these azole-treated cells. These results were in complete agreement with the proposed mechanism of action of azoles, which act by inhibiting ergosterol biosynthesis with a consequent accumulation of lanosterol. Concerning the MIC values, fluconazole was found to be the least effective drug. On the other hand, as determined from a comparison of the effects of the three azoles on the sterol content of the strains studied, no significant differences in efficacy were found among the tested drugs.

Effect of amphotericin B on the lipids of yeast cells of Sporothrix schenckii.

Yeast cells of five strains of Sporothrix schenckii were obtained for partial analysis of lipid composition. Quantitative analysis of lipids and sterols were completed, as well as qualitative analysis of sterols by thin layer chromatography and by ultraviolet spectra. These determinations were made on cells cultured in the absence and presence of amphotericin B at sub-MIC (minimum inhibitory concentration) levels. Marked alterations in lipid content were observed in the amphotericin B-treated cells. The major alterations were the reduction of total lipid (18.7-57.6%) and sterols (48.5-96.7%) after exposure to the polyenic antibiotic. It is concluded that amphotericin B altered the lipid profiles, especially sterols of S. schenckii.

A case of mycotic keratitis caused by Fusarium solani.

A 36-year-old black man, without history of systemic disease or ocular trauma developed a corneal infection in his left eye. He was treated with antibacterial antibiotic and corticosteroids for one month prior to diagnosis. Fungal hyphae and chlamydospores were found in a KOH preparation of the corneal scrapings, and positive cultures for Fusarium solani were obtained in Sabouraud dextrose agar. It is emphasized the cautious use of antibiotics and steroids in corneal diseases, and the need of considering the involvement of opportunistic fungi in the etiology of these infections.