Description:
The Mucorales, formerly known as Zygomycetes, have large ribbon-like aseptate hyphae (though occasional septa do occur). They have sporangia (sac-like structures) that produce yellow or brown spores. The sporangia are supported by sporangiophores which are connected by stolons. The production of these spores within sporangia is unique to the Mucorales (Zygomycetes). Rhizoids arise at contact points in some species (e.g. Rhizopus spp.). They are also fairly rapid growers, but this is not unique to this group, since Aspergullus spp. and others can grow fairly rapidly.The colonies are often grey.
Representative organisms:
Rhizopus (most common), Mucor, Actinomucor, Cokeromyces, Rhizomucor, Saksenaea, Apophysomyces, and Cunninghamella spp. Rhizopus and Mucor spp. will be discussed here. Mention will be made of Cunninghamella spp. Syncehphalastrum spp. are also occasionally found, mainly as a laboratory contaminant.
Epidemiology and disease:
Infections by these organisms are important in immunocompromised people, especially those with Diabetes Mellitus. These molds are normally found in decaying matter and stale bread (especially Mucor spp.). They are acquired by inhalation or ingestion, and occasionally by scrapes on the skin. They can cause a range of symptoms from thrombosis to infections of the nasal sinuses and brain, and less commonly the lungs, GI tract, skin, and subcutaneous tissues.
Diagnosis and Identification:
Direct samples are best, cultured on potato dextrose, 2% malt, and acidic agars. Growth of the mycelium is within 24-48 hours at 27-30° C. They grow rapidly and produce fluffy white/grey or brown hyphae.
