In Vitro Antifungal Activities of Amphotericin B, 5-fluorocytosine, Fluconazole and Itraconazole Against Cryptococcus Neoformans Isolated from Cerebrospinal Fluid and Blood from Patients in Serbia

Recently, geographic variations in resistance to agents commonly used in the treatment of cryptococcosis have been reported. Therefore, the antifungal susceptibilities of 31 clinical isolates of Cryptococcus neoformans, collected in Serbia during 10-year period, were investigated. Strains were isolated from cerebrospinal fluid (n=28) and blood (n=3), from patients with AIDS (n=26), lymphoma (n=4) and kidney transplant recipient (n=1). The minimal inhibitory concentrations (MICs) of amphotericin B, 5-fluorocytosine, fluconazole and itraconazole were determined by the E-test(®) method. The isolates were highly susceptible to amphotericin B (100% susceptibility at MIC<0.5 μg/mL) and 5-fluorocytosine (87.1% susceptibility at MIC ≤ 4 μg/mL). Geometric mean MIC of amphotericin B and 5-fluorocytosine were 0.102 μg/mL and 0.396 μg/mL, respectively. Fluconazole exhibited the lowest activity in vitro (48.4% susceptibility at MIC ≤ 8 μg/mL) with a significant resistance rate. The activity of itraconazole was also decreased (48.4% susceptibility at MIC ≤ 0.25 μg/mL). The geometric mean MIC of fluconazole stood at 15.14 μg/mL and of itraconazole was 0.144 μg/mL. Cross-resistance among azoles was not common (3.2%), but the parallel increase in fluconazole and itraconazole MIC has been observed (P<0.01). The low rate of susceptibility to fluconazole stresses the need for active antifungal surveillance of C. neoformans and of the corresponding data from different geographic regions.