Investigation of choice for cryptococcosis is -

Ans. is 'b' i.e., India ink o C. neoformans is best demonstrated in CSF by direct microscopy. The capsule is seen as a clear halo around the yeast cells in unstained wet preparations of CSF mixed with a drop of India ink or nigrosine. Methenamine silver stain would be the best choice for a tissue sample.CRYPTOCOCCUS NEOFORMANSo The only pathogenic yeasto Four capsular serotypes - A, B, C and Do It has polysaccharide capsuleo Most infections in immunocompromizedpatients are caused by serotype A.o Pigeon droppings commonly contains serotype A and D.o Eucalyptus tree contain serotype B.o It is urease positive.Mode of transmissionBy inhalation of the fungus into the lung (most common)Through skin or mucosa (some times).Laboratory diagnosis# Lumbar puncture is the single most useful diagnositc test.Laboratory diagnosisDirect microscopyCultureSerologyo Unstained wet preperationso Can be easily culturedo The most useful serological testof CSF mixed with drop offrom CSF on sabouroud'sls LPA test (Latex agglutinationIndia ink or nigrosineagartest for the detection of cryptococcaldemonstrate the capsule polysaccharide capsular antigen)as a clear halo o This is highly specific and sensitive; ando Methenamine silver or periodic gives better results than direct microscopyacid-Schiff are used for and cultures.staining a tissue sample.