Biomedical Engineering Reference
In-Depth Information
the mucosa into deeper tissue layers, and the transition to invasiveness is
often accompanied by a change in morphology from the yeast form, to
elongated cells (pseudohyphae) and hyphae. The most serious stage of candi-
diasis involves growth in blood (candidemia) and dissemination to distant
organs. Candida albicans is the most common pathogenic species, but there
are many more known pathogenic types, including Candida dubliniensis,
Candida glabrata, Candia parapsilosis, Candida rugosa, and Candida
tropicalis.
Ascomycota
Taphrinomycotina
Pneumocystidomycetes
Pneumocystidales
Pneumocystidaceae
*Pneumocystis
Pneumocystis, the sole pathogenic genus in Class Taphrinomycotina, was,
until recently, presumed to be a protozoa. Early papers invented a detailed
protozoan life cycle for Pneumocystis, complete with morphologically dis-
tinct developmental stages, that included cyst, trophozoite, sporozoite, and
intracystic bodies [107]. To be fair to the early taxonomists, the classification
of Pneumocystis was particularly difficult because the organism could not
be grown in culture. Owing to molecular analyses, we now know that
Pneumocystis is a fungus that grows as a yeast. The so-called trophozoite
stage of Pneumocystis is equivalent to the vegetative stage of well-studied
Schizosaccharomyces pombe, a non-pathogenic member of Class
Taphrinomycotina. The yeasts form an enclosed cyst, which eventually rup-
tures, releasing spores. These different forms of Pneumocystis comprise the
various morphologic forms of the fungus that are seen in histologic sections
of infected lungs. Pneumocystis jerovicii (formerly Pneumocystis carinii),
produces pneumonia in immune-deficient individuals. AIDS patients are
particularly vulnerable to Pneumocystis infections.
Ascomycota
Pezizomycotina
Dothideomycetes
Dothideales
Dothioraceae
*Hortaea
Pleosporomycetidae
Pleosporales
Testudinaceae
*Neotestudina
Hortaea werneckii causes tinea nigra, from the Latin “tinea,” meaning worm
and “niger,” meaning black. Tinea, also known as ringworm, is a localized
