Section IV - Medical Mycology By Dr. Kareem Lilo
o Nonculture Candida detection tests
(d) D-inositol assay, and (e) 1,3-beta-D-glucan assay. Beta-Dglucan assay is a broad-spectrum test
that detects Candida as well as Aspergillus, Fusarium, Acremonium, and Saccharomyces species. This
is a highly specific and sensitive test.
Antifungal therapy forms the mainstay of treatment of the infections caused by Candida. These agents
include azoles ( fluconazole, triazole, ketoconazole), nystatin, and amphotericin is becoming
increasingly important worldwide .
A broad spectrum of diseases in humans ranging from direct invasion to hypersensitive reactions are
caused by Aspergillus species. Although more than 100 species have been described, the majority of
human diseases are caused by Aspergillus fumigates and Aspergillus niger, and less frequently by
Aspergillus flavus and Aspergillus clavatus.
Figure(74-2)Candida albicans showing formation of the germ
Section IV - Medical Mycology By Dr. Kareem Lilo
Aspergillus species are molds.
They have septate hyphae that form V-shaped dichotomous branches (Figure 4-5). The
Aspergillus species are identified by (a) their morphological features, (b) the pattern of
conidiophores development, and (c) the color of the conidia.
The presence of septate hyphae that branch at 45° angles is the typical feature of Aspergillus
species hyphae. The hyphae in tissues are best demonstrated with silver stains. The walls of
the hyphae are more or less parallel, unlike those of Mucor and Rhizopus, which are more or
Aspergillus species rarely cause infections in immunocompetent individuals. They cause invasive
infections mostly in the patients who are immunocompromised either due to (a) use
of immunosuppressive drugs, (b) underlying lung diseases, or (c) immunodeficiency diseases, such
as HIV. In immunocompromised host, Aspergillus species cause invasion of the blood, thereby
causing infarction, hemorrhage, and necrosis of lung tissues. Aspergillus spp. also produces toxic
metabolites that inhibit macrophage and neutrophil phagocytosis, facilitating
dissemination of the infection.
Aspergillus species unlike Candida species do not form the part of normal flora of humans. They are
ubiquitous in the environment; hence transmission of infection is mostly exogenous.
In immunocompetent hosts, Aspergillus species may primarily affect the lungs, causing four main
syndromes including (a) allergic bronchopulmonary aspergillosis, (b) chronic necrotizing
aspergillus pneumonia, (c) aspergilloma, and (d) invasive aspergillosis.
Figure( 4-5) Aspergillus species with septate hyphae that form V-shaped
Section IV - Medical Mycology By Dr. Kareem Lilo
which have colonized in tracheobronchial tree. This condition occurs often in association with
Chronic necrotizing pulmonary aspergillosis: It is a subacute infection seen in patients with some
degree of immunosuppression. The condition occurs in conjunction with alcoholism, underlying
lung disease, or chronic corticosteroid therapy.
may have been caused earlier by tuberculosis, sarcoidosis, cystic fibrosis, and
emphysematous bullae. The condition is characterized by the presence of a ball of fungus within the
cavity. The fungus, however, does not invade the cavity. It may cause hemoptysis.
Invasive aspergillosis: It is a rapidly progressive infection in patients who are severely
immunocompromised. The condition is mostly fatal. In immunocompromised host, Aspergillus
organisms cause a disseminated disease, leading to endophthalmitis, endocarditis, and abscesses in
the viscera, such as liver, spleen, kidney, soft tissues, and bone.
Laboratory diagnosis of invasive aspergillosis or chronic necrotizing aspergillus pneumonia depends
on demonstration of Aspergillus in tissue by direct microscopy and culture.
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