Biomedical Engineering Reference
In-Depth Information
Taphrinomycotina
Microsporidia (Chapter 37)
There are four classes of fungi that contain pathogenic organisms: Class
Zygomycota (Chapter 34), Class Basidiomycota (Chapter 35), Class
Ascomycota (Chapter 36), and Class Microsporidia (Chapter 37).
Like all the major divisions of fungi, Class Zygomycota is characterized
by its sexually reproductive form. In the zygomycotes, the sexual form is the
zygospore. As with much of clinical mycology, the defining morphologic
features of the zygomycotes are never observed in clinical specimens. In tis-
sues, these organisms are present as hyphal forms, without a yeast phase.
In the laboratory culture dish, they are present as hyphal colonies with asex-
ual reproductive forms (sporangia containing spores, and free spores). The
identification of species is typically made by expert evaluation of the avail-
able structures: hyphae and sporangia. In many instances, members of Class
Zygomycota can be distinguished from members of the other major classes
of fungi (i.e. ascomycotes and basidiomycotes) by three features: (1) non-
septate hyphae, (2) wide hyphae with thick walls, and (3) absence of yeast
phase. Non-septation of hyphae refers to a type of hyphal growth wherein
walls (i.e. septations), do not separate individual hyphal cells, and in which
multiple nuclei float in the filamentous hyphae (i.e. coenocytic growth).
Most of the pathogenic zygomycotes are non-commensal opportunists.
They grow in soil, water, or air, on plants or on dung. Humans are constantly
being exposed to their infective spores, by inhalation or by ingestion.
Virtually all infections occur in patients who provide these fungi with a
physiologic opportunity for growth (e.g., malnutrition, diabetes, advanced
cancer, immunodeficiency, or an infection portal such as an indwelling
catheter or a intravenous line).
Zygomycota
Mucormycotina
Mucorales
Mucoraceae
*Rhizopus
*Mucor
*Absidia
Syncephalastraceae
*Syncephalastrum
Entomophthoramycotina
Entomophthorales
Basidiobolaceae
*Basidiobolus
Ancylistaceae
*Conidiobolus
