The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis. There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The majority of human illness is caused by the Mucorales.
Organisms of the class Zygomycetes were first noted to cause disease in humans in publications from the 1800’s.
PDF Doc – 66 pages. – Zygomycetes-in-Human-Disease
Opportunistic mycoses are infections due to fungi with low inherent virulence which means that these pathogens constitute an almost limitless number of fungi. These organisms are common in all environments.
The disease equation:
|Number of organisms x Virulence
With opportunistic infections, the equation is tilted in favor of “disease” because resistance is lowered when the host is immunocompromised. In fact, for the immunocompromised host, there is no such thing as a non-pathogenic fungus.
The fungi most frequently isolated from immunocompromised patients are saprophytic (i.e. from the environment) or endogenous (a commensal). The most common species are Candida species, Aspergillus species, and Mucor species.
The upward trend in the diagnoses of opportunistic mycoses reflects increasing clinical awareness by physicians, improved clinical diagnostic procedures and better laboratory identification techniques. Another important factor contributing to the increasing incidence of infections by fungi that have not been previously known to be pathogenic has been the rise in the number of immunocompromised patients who are susceptible hosts for the most uncommon agents. Patients with primaryimmunodeficiencies are susceptible to mycotic infections particularly when cell-mediated immunity is compromised. In addition, several types of secondary immunodeficiencies may be associated with an increased frequency of fungal infections.
OPPORTUNISTIC MYCOSES – PDF
Content Source-Microbiology and Immunology On-line | University of South Carolina School of Medicine