The Southeastern Asian house mouse (Mus musculus castaneus Linn.) as a new passenger host for Cryptococcus neoformans var. grubii molecular type VNI.

We describe Mus musculus castaneus as a new mammalian host for Cryptococcus neoformans var. grubii (VNI). Eighteen apparently healthy adults and pups of the rodent were collected from human dwellings in Varanasi, a city of India. Both clinical and behavioral examinations of the rodents did not reveal any sign of the disease. Among visceral organs, histological examination of only liver exhibited the presence of single celled, encapsulated, Southgate's mucicarmine positive fungal structures consistent with C. neoformans. Nevertheless, culture of tissue homogenates of brain, lungs, liver, and kidneys yielded white colonies on Sabouraud's dextrose agar and brown mucoid colonies of C. neoformans on Staib's and Tobacco agar media. The pathogen was isolated from habitat soil as well as fresh faeces of the animals. All isolates were urease positive, nitrate and canavanine-glycine bromothymol blue negative, exhibited phenoloxidase activity and grew at 37°C. The isolates were identified as C. neoformans var. grubii with ITS primers and unique marker (GACA)4. The pathogen when inoculated in immunosuppressed mice showed low pathogenicity. To our knowledge, we for the first time report case cluster of Mus musculus castaneus as new passenger host for C. neoformans var. grubii (VNI).