TOC AGAR

Description

Candida are yeast-like fungus forming normal flora inhabiting the mouth and throat, the intestinal tract and the genital tract. Under certain conditions, they cause life-threatening diseases particularly in immunocompromised patients. Candida albicans is the species most commonly isolated from patients with nearly all forms of candidiasis. Cryptococcus neoformans is often cultured from the urine of patients with disseminated infection. Cryptococcosis is one of the defining diseases associated with AIDS. TOC Agar is a multi-purpose medium developed by Fleming et al for the rapid, presumptive identification of C. albicans and C. neoformans. Both species are common clinical isolates that may be presumptively identified by specific morphological characteristics. C. albicans and C. stellatoides may be presumptively identified on this medium by the formation of germ tubes and chlamydospores. For the germ tube test, lightly touch a single colony from TOC Agar with a loop or Pasteur pipette; remove excess inoculum and then emulsify the yeast cells in 0.5 ml of horse or other serum in a small test tube with a loose cotton-wool plug. Failure to achieve a light inoculum inhibits germ-tube formation. Incubate at 37?C in a water bath for 2-4 hours. A drop of suspension is then placed on a glass slide and covered with coverslip. Microscopic examination of typical C. albicans reveals thin germ tubes 3 to 4 mm in diameter and up to 20 mm long; unlike pseudohyphae that are not constricted at their point of origin.