Candida tropicalis

Candida tropicalis is a species of yeast in the genus Candida. It is a common pathogen in neutropenic hosts, in whom it may spread through the bloodstream to peripheral organs. For invasive disease, treatments include amphotericin B, echinocandins, or extended-spectrum triazole antifungals. In the history of fungi, the name of genus Candida, derived from the family Debaryomycetaceae, comes from the Latin term 'candidus' which has the meaning of “glowing white” and also refers to as smooth and glistering. Genus Candida referred to any asexual yeast without any of the following characteristics: production of acetic acid, pigments of colours red, pink or orange, arthroconidia, unipolar or bipolar budding, enteroblastic-basipetal budding, blastoconidia formation on sympodulae, buds formation on stalks, triangular cells, needle-shaped terminal conidia, and having the ability to grow on inositol as a sole carbon source. Although there are 200 species identified in this genus, the taxonomy remains undefined and incomplete due to several reasons such as changing the words for some representations, the finding of new species and the reclassification of identified old species. This genus no longer includes species that test positive to diazonium blue B (DBB). The defunct genera Oidium and Monilia were used to represent the genus Candida. In the genus Candida, there are other species that are synonym of Candida tropicalis. Candida albicans is taxonomically close to C. tropicalis sharing many pathogenic traits whereas C. maltosa and C. sake are physiologically similar to C. tropicalis but they can be differentiated by the growth at 35 °C (only C. sake showing negative) and assimilation of soluble starch (only C. tropicalis showing positive starch assimilation). C. tropicalis is easily identified using phenotypic and molecular methods. The identification of species in the genus Candida is relies on morphological and physiological features. Species in the genus are vegetative cells which reproduces asexually by budding, and the structure, shape, septation, color and arrangement of buds is useful for identification. The production and appearance of pseudohyphae and blastoconidia may also be useful for identification. Physiological profiles relating to carbon and nitrogen utilization are of value in determining species, as are the presence certain distinctive biochemical features. Increasingly, molecular genetic methods such as DNA sequencing are used as primary tools for the accurate determination of species identifications in this group. C. tropicalis is a vegetative cell with the shape from round to oval ranging from approximately 2 – 10 micrometers. A mould exhibits dimorphism forming a single-celled yeast or so-called blastoconidia which reproduces by simple buddingㄡ Conidia is the asexual unit that are produced by budding of the tips or walls of the hyphae. Conidia is a type of simple and unicellular body that could take the form of multicellular cell with different shapes, sizes, and colors. Microconidia is used to refer to small and unicellular conidia whereas macroconidia refers to large and multicellular conidia. There are different media on which C. tropicalis can grow effectively. A common medium used is the Sabouraud’s agar which contains peptone and sugar. This is enough for identifying the species but with a disadvantage of promoting mycelial growth and suppressing conidia formation. Another commonly used medium is the cornmeal agar which is useful in inducing formation of conidia. Potato-glucose, potato-carrot, tomato juice, lima bean and others are also types of media used for growth. The optimal temperature for growth is between 25–35 °C (77–95 °F) and growth is enhanced if sugar or fat is added in the medium. Colony of C. tropicalis are white, smooth and butyrous with a fringed border. C. tropicalis reproduces asexually by the production of blastoconidia through budding. As blastoconidia increase in number they may elongate in shape producing structures called the pseudohyphae. Under specific conditions of reduced oxygen level in host tissues, submerged colonies in agar medium, or in the presence of 5-10% CO2, true, septate hyphae may form. This test is to detect yeast’s ability to produce enzyme urease. Once there's a compatible substrate, urease will split urea to produce ammonia increasing the pH. C. tropicalis is found to be urease negative.