Zygomycophyta

Zygomycophyta are a group of fungi that contain three important pathogens known as opportunistic fungi. The three organisms are Mucor, Rhizopus, and Absidia. They are found in spoil, and their sporangiospores are inhaled from the environment to cause disease especially in ketoacidotic, diabetic, leukemic, and other immunocompromised individuals. They are known to cause rhino-cerebral infections as the subject breathes them in from the environment (as sporangiospores). The fungi spreads from the sinuses, ignoring anatomical barriers, and progress to brain tissue particularly in patients with uncontrolled diabetes and leukemia. Patients with lymphoma and burns are also at risk with these pathogens.

A study published in the American Journal of Perinatology in 2009 showed life-threatening infection with neonates, 77% of which were premature and a large majority of the isolates were Rhizopus (72%). The overall mortality was 64%.

Mucor
Mucor is a fungus known for its dimorphism. When deprived of oxygen and other nutrients, they become spherical and multipolar, budding yeasts. In the presence of oxygen or within the body, they become branching coenocytic hyphae from a single sporangiospore. The most common underlying disease are hematological malignancies (in high income countries) and uncontrolled diabetes (in developing countries).

Rhizopus
Rhizopus are commonly seen in plants, animals, and bio-industrial fermenters. The major species identified include R. oryzae, R. azygosporus, R. microsporus, R. stolonifer, R. arrhizus, and R. delemar. Documented cases with poorly controlled diabetes mellitus have high mortality rates.

Absidia
Documented species to have caused disease by Absidia include A. corymbifera seen in a premature newborn and burn patients. Absidia represents only 2-3% of all Zygomycophyta infections as they are thought to rarely infect immuno-competent individuals. Armed with proteolytic enzymes, Absidia also have the potential for angioinvasive disease.

Symptoms of disease
Rhinocerebral infection is characterized by paranasal swelling with necrotic tissues. Patient may have hemorrhagic exudates (tissue fluid from lesions tinged with blood) from the nose and eyes as the fungi penetrate through blood vessels and other anatomical structures.

In primary cutaneous disease of Zygomycophyta, the lesions are usually painful and necrotic, with black eschar, accompanied by a fever. Patients will usually present with a history of poorly controlled diabetes or malignancy. Myocutaneous infectious may lead to amputation.

Pulmonary tract infections seen with lung transplant patients, who are at high risk for fatal invasive mycoses.

Diagnosis
Diagnosis is done with potassium hydroxide (KOH) preparation in tissue. On light microscopy, there will be broad, ribbon-like septate hyphae with 90 degree angles on branches. KOH wet mount of the black eschar will show aseptate fungal hyphae with right angle branching. Periodic Acid Schiff (PAS) staining will reveal similar broad hyphae in the dermis and cutis. Fungal culture can also confirm the organism. Diagnosis remains difficult due to the lack of laboratory tests as mortality remains high. In 2005, a multiplex PCR test was able to identify five species of Rhizopus and may prove useful as a screening method for visceral mucormycosis in the future.

Clinical approach to diagnosis includes radiologic, where more than ten nodules and pleural effusion are associated to pulmonary forms of the disease. In CT, a reverse halo sign is noted. Direct microscopy and histopathology, and cultures remain the gold standards for diagnoses. Zygomycophyta share close clinical and radiological features to Aspergillosis. Invasive procedures such as bronchial endoscopy and lung biopsy may be necessary to confirm pulmonary diagnosis are no validated indirect tests are available. Quantitative polymerase chain reaction to detect serum DNA of the pathogen shows promise.

Treatment
Due to Zygomycophyta's rapid growth and invasion, it presents with a high fatality rate. Treatment must begin immediately with debridement of the necrotic tissue plus Amphotericin B. Complete excision of the infectious tissue may be required as suspected dead tissue must be excised aggressively. Documented case of conservative surgical drainage, intravenous amphotericin B in and insulin-dependent diabetic have proven effective in sino-orbital infection.