Multilocus sequence typing of the agents of cryptococcosis in the Rio Negro river basin, Brazilian Amazon region



Cryptococcosis is a life-threatening systemic mycosis affecting humans and animals worldwide. The disease is acquired by inhalation of infectious propagules of the Cryptococcus neoformans/C. gattii species complexes from the environment. Pioneering environmental studies on cryptococcosis in AIDS in Central Africa and in Brazil demonstrated that individuals living in contaminated dwellings are at risk to acquire cryptococcosis from indoor contamination. In the heart of the Amazon rainforest, a study revealed the occurrence of C. gattii VGII in dust samples from dwellings and wood poles in a remote human settlement in the Rio Negro Microregion, Amazon, Brazil. The high density of cryptococcal colonies suggested that the local inhabitants are daily exposed to the yeast. In this study, we disclosed new evidences of C. neoformans and C. gattii 7 out of 79 investigated human dwellings and two out of 10 wood poles in the Rio Negro Basin, Brazilian Amazon. In one of the positive dwelling (An/P9) 200 CFU/g of dark brown colonies were found, and identified as C. gattii VGII and in another dwelling (Re/P15) 300 CFU/g of dark brown colonies were found and identified as C. gattii VGII and C. neoformans VNI. Forty-eight C. gattii and 18 C. neoformans isolates were subtyped using the ISHAM MLST consensus scheme. The most common C. gattii subtypes were ST7 (Vancouver Island Outbreak subtype VGIIb, 24/48) and ST20 (Vancouver Island Outbreak subtype VGIIa, 11/48). Amongst the 18 C. neoformans (VNI) isolates ST93 and ST5 were identified, showing a clonal population. Mating type analysis demonstrated all isolates were MATα. The identified MLST subtypes from the environmental isolates in the microregion of Rio Negro indicate domiciliary dust as well as wood poles as a potential source for human infection with different subtypes of C. gattii VGII and C. neoformans VNI MATα and confirmed the link between remote human settlements in the Rio Negro river basin and the Pacific North West outbreak of cryptococcosis.