term zygomycosis describes

Description:

The term zygomycosis describes in the broadest sense any infection due to a member of the Zygomycetes. These are primitive, fast growing, terrestrial, largely saprophytic fungi with a cosmopolitan distribution. To date, some 665 species have been described although infections in humans and animals are generally rare. Medically important orders and genera include:
1. Mucorales, causing subcutaneous and systemic zygomycosis (Mucormycosis) – Rhizopus, Mycocladus (Absidia), Rhizomucor, Mucor, Cunninghamella, Saksenaea, Apophysomyces, Cokeromyces and Mortierella.
2. Entomophthorales, causing subcutaneous zygomycosis (Entomophthoromycosis) – Conidiobolus and Basidiobolus.

Clinical manifestations:

Zygomycosis in the debilitated patient is the most acute and fulminate fungal infection known. The disease typically involves the rhino-facial-cranial area, lungs, gastrointestinal tract, skin, or less commonly other organ systems. It is often associated with acidotic diabetes, starvation, severe burns, intravenous drug abuse, and other diseases such as leukemia and lymphoma, immunosuppressive therapy, or the use of cytotoxins and corticosteroids, therapy with desferrioxamine (an iron chelating agent for the treatment of iron overload) and other major trauma. The infecting fungi have a predilection for invading vessels of the arterial system, causing embolization and subsequent necrosis of surrounding tissue. A rapid diagnosis is extremely important if management and therapy are to be successful.

Rhinocerebral zygomycosis:

Predisposing factors include uncontrolled diabetes mellitus or acidosis, steroid induced hyperglycemia, especially in patients with leukemia and lymphoma, renal transplant and concomitant treatment with corticosteroids and azathioprine. Infections usually begin in the paranasal sinuses following the inhalation of sporangiospores and may involve the orbit, palate, face, nose or brain.

Mucorales:

Mucorales are rapidly growing fungi including two families, the Mucoraceae and Cunninghamellaceae. Mucorales usually causes infection in individuals with compromised immune systems due to drugs such as systemic steroids, and diseases such as lymphoma and poorly controlled diabetes. The fungi invade blood vessels and cause mucormycosis, an acute, rapidly spreading and fulminant systemic mycosis. Rhinocerebral (nose and brain), lung, gastrointestinal and abdomin-pelvic, cutaneous and widespread forms have been reported. The mortality rate is very high.Cutaneous lesions from Mucorales are due to traumatic implantation or secondary to spread via the bloodstream to the skin. Mucorales infection may result in plaques, pustules and abscesses or necrotic, ulcerated lesions.

Pathogenicity and Health Effects:

Rhizopus species are among the fungi causing the group of infections referred to as zygomycosis.  Zygomycosis is now the preferred term over mucormycosis for this angio – invasive disease.  Rhizopus arrhizus is the most common cause of zygomycosis and is followed by Rhizopus microsporus var. rhizopodiformis.Zygomycosis infection includes mucocutaneous, rhinocerebral, genitourinary, gastrointestinal, pulmonary, and disseminated infections.  The most frequent predisposing factors for zygomycosis include diabetic ketoacidosis and immunosuppression due to various reasons, such as organ transplantation and other factors such as desferoxamine treatment, renal failure, extensive burns, trauma, and intravenous drug use which may also predispose to development of zygomycosis.  Heatstroke has been described as a risk factor for disseminated zygomycosis as well.  Contaminated adhesive tapes and wooden tongue depressors have been reported to lead to nosocomial outbreaks of zygomycosis.  Vascular invasion that causes necrosis of the infected tissue, and perineural invasion are the most frustrating features of these infections. Zygomycosis is frequently considered as fatal infection.

Susceptibility:

Limited data are available on the in vitro susceptibility profile of Rhizopus species.  Amphotericin B, based on the study comparing the in vitro activity of amphotericin B, ketoconazole, itraconazole, and voriconazole against Rhizopus arrhizus strains, yielded low MICs.  The MICs of ketoconazole, itraconazole, and voriconazole were similar to one another while slightly higher than those of amphotericin B.  Considerably high MICs were detected against Rhizopus arrhizus by fluconazole.Caspofungin and anidulafungin appeared to have limited activity against Rhizopus species.  Azasordarin derivatives and posaconazole, on the other hand, were found to be active in vitro against Rhizopus arrhizus.  Appeared to be active against Rhizopus species were posaconazole and ravuconazole compared to voriconazole as well.