Antifungal drug susceptibility of Cryptococcus neoformans from clinical sources in Nairobi, Kenya

The serotypes and mating types of 80 clinical isolates of Cryptococcus neoformans from Kenya were studied and subjected to broth microdilution susceptibility testing to amphotericin B (AMP), flucytosin, fluconazole (FLC), itraconazole (ITC) and miconazole (MCZ). The isolates included C. neoformans var. grubii- 75 of 80 (serotype A; 93.7%), C. neoformans var. neoformans- three of 80 (3.8%) and C. neoformans var. gattii- two (serotype B; 2.5%). Mating experiment confirmed all the isolates to be α-mating type. Seventy-eight (97.5%) of the isolates had minimum inhibitory concentration (MIC) of ≤0.5 μg ml^-1 to AMP and at 1 μg ml^-1, 100% of the isolates were inhibited. Flucytosin resistance was observed in 21% with MIC in which 90% of the isolates were inhibited (MIC₉₀) of 64 μg ml ^-1. Only 23.8% of the strains were susceptible to FLC with 65% susceptible dose-dependent (SDD) and 11.2% resistant. Itraconazole susceptibility was 61.3% while the rest were either SDD or resistant. The MIC₉₀ for ITC and MCZ were 0.5 and 2 μg ml^-1 respectively. The study reports the serotypes, mating types and highlights the existence of azoles resistance in C. neoformans in Nairobi which calls for antifungal drug resistance surveillance as prophylactic use of FLC increases because of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic in sub-Saharan Africa.