Treatment of experimental cryptococcosis with SCH 39304 and fluconazole

Itraconazole and flucytosine+itraconazole combination in the treatment of experimental cryptococcosis in hamsters

The efficacy of two different daily doses of itraconazole (ITRA) and the combination of flucytosine (5-FC) with ITRA in the treatment of an experimental model of cryptococcosis in hamsters was studied. Five groups of 20 animals each were inoculated by the intracardiac route with 10(5) cells of Cryptococcus neoformans. Treatment started 3 days after the infection, and was administered by gavage for 30 days. ITRA was applied at a daily dose of 25 mg kg-1 or 50 mg kg-1 and the combination of 5-FC and ITRA was given at 75 mg kg-1 day-1 or 50 mg kg-1 day-1 respectively. One group of 20 hamsters received the vehicle and was used as a control group. Treatment evaluation was based on the following parameters: number of surviving animals 60 days after the infection; presence of encapsulated yeasts on microscopic examination of wet preparations of brain, lungs, liver, spleen and kidneys at necropsy; and brain qualitative (massive seeding) and quantitative cultures (determination of colony forming units, CFU). ITRA 50 (50 mg kg day-1) was the most effective treatment according to the studied parameters; 70% of brain cultures became negative and 95% of the treated hamsters survived to the end of the study period. ITRA efficacy was dose dependent. The combination of ITRA with 5-FC was less effective than administering the drugs separately; the reason for this finding is not known. The results obtained in this study should encourage the use of high doses of ITRA in cases of disseminated cryptococcosis in humans.

Effect of amphotericin B on the lipids of five different strains of Cryptococcus neoformans

Cells of five strains of Cryptococcus neoformans 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 the ultraviolet spectra. Such determinations were made on cells cultured in the absence and presence of amphotericin B at sub-MIC (minimal inhibitory concentration) levels. Marked alterations of the lipid and sterol contents were observed in the amphotericin B-treated cells. Moreover, ergosterol disappeared in these antibiotic-exposed cells. It is concluded that amphotericin B altered the lipid profiles, especially sterols of C. neoformans.

Pathogenesis of pulmonary Cryptococcus neoformans infection in the rat

The pathogenesis of Cryptococcus neoformans pulmonary infection in the rat was studied after intratracheal inoculation. Lungs were examined at various times following infection for histopathology in conjunction with macrophage markers, proliferating cell nuclear antigen (PCNA), and capsular glucuronoxylomannan (GXM) antigen. Serum GXM, immunoglobulin M (IgM) and IgG titers and organ fungal burden were compared with pathological findings. C. neoformans organisms were in the lung parenchyma 2 h postinoculation, and GXM antigen was present in surrounding tissues shortly thereafter. Extrapulmonary dissemination occurred early in infection. Two phases of host cellular inflammatory response were discernible: early local macrophage recruitment at 2 to 4 days followed by granulomatous inflammation, which reached maximum intensity 14 days after infection. The granulomatous phase was preceded by lymphocyte influx with macrophage proliferation and maturation into epithelioid histiocytes; this was paralleled by a shift of yeasts from extracellular to intracellular spaces. Tissue IgG deposits, serum IgG to GXM, and localization of tissue GXM immunoreactivity to epithelioid cells were noted at 2 to 4 weeks. A 10-fold decrease in lung fungal burden occurred 25 days postinfection and was associated with resolving granulomas, fewer proliferating cells, and decreased tissue GXM. The present study demonstrates that (i) C. neoformans penetrates the lung parenchyma shortly after infection; (ii) immunocompetent rats control pulmonary cryptococcosis efficiently, with minimal extrapulmonary dissemination and low levels of serum GXM; and (iii) macrophage activation is likely to play a crucial role in limiting C. neoformans infection in the rat lung.

Treatment of coccidioidomycosis with SCH 39304

A new oral triazole antifungal, SCH 39304, was administered to 54 patients with progressive infections due to Coccidioides immitis from six collaborating centers. Patients were grouped according to site of infection including chronic pulmonary (25), bone/joint (17) and skin/soft tissue (12). The median age was 40 years; 83% were male, 52% white, 13% HIV-infected and 35% had failed previous therapy. The majority of patients were treated with either 100 mg or 200 mg day-1. One patient on renal dialysis received 300 mg day-1. Baseline abnormalities were reassessed for evidence of efficacy every 4 months and expressed in a standardized scoring system. Cumulative overall response rates at 4, 8 and 12 months were 7%, 36% and 66% respectively. Twelve month response rates by disease were 77% (pulmonary), 62% (skin/soft tissue) and 31% (bone/joint). Fifteen patients failed therapy although seven of these were still on treatment when the study was discontinued. Two failed due to toxicity. Possible symptoms or signs of toxicity occurred in 24 (44%) patients and were generally mild. SCH 39304 is an effective and well tolerated therapy for progressive forms of coccidioidomycosis.

Synergistic postantifungal effect of flucytosine and fluconazole on Candida albicans

The in vitro efficacy of flucytosine and fluconazole, separately and in combination, with respect to induction of a postantifungal effect (PAFE) on Candida albicans was studied. PAFE refers to the persistent suppression of fungal cell growth following a short period of exposure to an antifungal agent. A turbidometric method was used to measure cell growth and to quantitate the PAFE following exposure of C. albicans yeast cells to different concentrations of the two agents for 2 h. The PAFE was determined by the difference in time (h) required for growth of the control and test cultures to increase to the 0.5 absorbance level following removal of the drug by dilution. Minimum (MIC) and fractional inhibitory concentration determinations were made and the data used for selecting the concentrations used in the PAFE evaluations. A synergistic interaction of the two drugs at concentrations well below their individual MICs was evidenced. Flucytosine:fluconazole ratios of 1:16-1:32 at concentrations ranging from 0.024-0.098 micrograms ml-1 and from 0.78-1.56 micrograms ml-1, with flucytosine and fluconazole, respectively, induced PAFEs which persisted for 2.5 h longer than those achieved when each of the two agents was assayed separately.