CAFFEIC ACID FERRIC CITRATE TEST AGAR (CAFC MEDIUM)

Description

Cryptococcus neoformans is an encapsulated basidiomycete yeast-like fungus. C. neoformans have affinity for avian habitats and has been isolated from soil contaminated by bird droppings. It causes diseases in apparently immunocompetants, as well as immunocompromised hosts. The most susceptible are patients with T-Cell deficiencies. C. neoformans is the fourth most common cause of life-threatening infection in patients with AIDS. Caffeic Acid Ferric Citrate Test Agar is used for the rapid identification and differentiation of C. neoformans from other species of Cryptococcus. This medium was described by Hopfer and Blank. The medium contains caffeic acid which is a selective agent for C. neoformans. Caffeic acid is an O-diphenol compound which can be oxidized by phenoloxidase enzyme to produce dark brown melanin pigmentation. C. neoformans has a unique ability to produce melanin or melanin-like pigment from p- and o-diphenols and can be differentiated from Candida albicans. Thus, Caffeic acid causes pigment production of C. neoformans in the presence of (iron) ferric citrate. Growth of C. neoformans on this medium should be compared with same organism on another medium before inoculation to see whether colonial growth is naturally pigmented. False negative reactions may occur. Pigment production is delayed during luxurious growth. Other Cryptococci may become pigmented after 3-4 days of inoculation, but they are not so intensely coloured and can therefore be distinguished from C. neoformans.