Mucormycosis: Introduction, Pathogenecity, Labotarory Diagnosis

Mucormycosis: Introduction, Pathogenecity, Labotarory Diagnosis and Treatment

Mucor and Its Structures in LPCB

Mucor and its structures, sporangiophore, sporangium, spores, and lacking rhizoid (which is the main feature that differentiates mucor from Rhizopus and Absidia) in LPCB as shown above image. Medically important species of the genus, Mucor are as follows-

M. circinelloides
M. indicus
M. ramosissimus
M. amphibiorum
M. hiemalis
M. racemosus
M. ellipsoideus

Classification of Causative agents of Mucormycosis

Kingdom: Fungi
Division: Zygomycota
Class: Mucoromycetes
Order: Mucorales
Family: Mucoraceae
Genus: Mucor

Rhizopus

Absidia

Pathogenicity

Mucormycosis is a serious but rare fungal infection caused by three genera of class micromycetes, Mucor, Rhizopus, and Absidia. These fungi are saprophytes of soil, manure, and decaying vegetables. Mucormycosis mainly affects people who with weakened immune systems. It most commonly affects the sinuses or the lungs after inhaling fungal spores from the air, or the skin after the fungus enters the skin through a cut, burn, or another type of skin injury. Absidia may also cause keratitis. However, it can occur in nearly any part of the body even bone to brain. Gastrointestinal mucormycosis may occur in malnutrition, uremia, and diarrhoeal diseases.

Laboratory Diagnosis of Mucormycosis

Specimens

Specimens depend on the nature of infection sites. They may be scrapping from the lesions, pus, sputum, nasal discharge, etc.

Direct Microscopy

KOH mount: Presence of fungal elements ( non-septate hyphae)

Histopathological examination: Histological sections stained H & E stain reveal the presence of hyphae.

Culture: Colonies are very fast-growing, cottony to fluffy, white to yellow, becoming dark grey, with the development of sporangia.

LPCB preparation: Presence of sporangia, columella with a conspicuous collarette and sporangiospores as shown above picture and below video-

Growth of Absidia on SDA and its LPCB preparation under the microscope as shown below-

Treatment of Mucormycosis

There is very limited data for antifungal susceptibility testing (AFST) and thus AFST should be performed for individual strains.

Common antifungal drugs are-

Fluconazole
Itraconazole
Posaconazole
Amphotericin B
Flucytosine and
Voriconazole.

Note: Some drugs vary according to genus to genus and even species to species.

Keynotes

Mucormycosis was previously called zygomycosis.
The genus Mucor can be differentiated from Absidia, Rhizomucor, and Rhizopus by the absence of stolons and rhizoids.

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