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.[1] Patients with lymphoma and burns are also at risk with these pathogens.[2]
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%.[3]
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.[4] The most common underlying diseases are hematological malignancies (in high income countries) and uncontrolled diabetes (in developing countries).[5]
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.[6][7] Documented cases with poorly controlled diabetes mellitus have high mortality rates.[8]
Absidia
Documented species to have caused disease by Absidia include A. corymbifera seen in a premature newborn[9] and burn patients. Absidia represents only 2-3% of all Zygomycophyta infections as they are thought to rarely infect immunocompetent individuals. Armed with proteolytic enzymes, Absidia also have the potential for angioinvasive disease.[10]
Symptoms of disease
Rhinocerebral infection is characterized by paranasal swelling with necrotic tissues. Patients 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.[1]
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.[11] Myocutaneous infections may lead to amputation.
Pulmonary tract infections seen with lung transplant patients, who are at high risk for fatal invasive mycoses.[12]
Diagnosis
Diagnosis is done with potassium hydroxide (KOH) preparation in tissue. On light microscopy, there will be broad, ribbon-like hyphae with 90 degree angles on branches.[1] 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.[13] 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.[7]
Clinical approach to diagnosis includes radiologic examination, where more than ten nodules and pleural effusion are associated with pulmonary forms of the disease. In CT, a reverse halo sign is noted. Direct microscopy and histopathology, and cultures remain the gold standards for diagnosis.[5] 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 if no validated indirect tests are available. Quantitative polymerase chain reaction to detect serum DNA of the pathogen shows promise.[14]
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.[1] Complete excision of the infectious tissue may be required as suspected dead tissue must be excised aggressively.[13] Documented case of conservative surgical drainage, intravenous amphotericin B and insulin-dependent diabetic have proven effective in sino-orbital infection.[15]
References
- ↑ 1.0 1.1 1.2 1.3 Moscatello, Kim (2013). USMLE Step 1: Immunology and Microbiology Lecture Notes. Chicago: Kaplan Publishing. pp. 430–431. ISBN 978-1625232557. Search this book on
- ↑ Ayaz M, Moein R. Myocutaneous Mucormycosis in a Diabetic Burnt Patient Led to Upper Extremity Amputation; A Case Report. Bull Emerg Trauma. 2017 Jan;5(1):58-62. PMID 28246626; PMCID: PMC5316139.
- ↑ Roilides E, Zaoutis TE, Katragkou A, Benjamin DK Jr, Walsh TJ. Zygomycosis in neonates: an uncommon but life-threatening infection. Am J Perinatol. 2009 Sep;26(8):565-73. doi: 10.1055/s-0029-1220775. Epub 2009 Apr 23. PMID 19391079; PMCID: PMC6999698.
- ↑ Orlowski M. Mucor dimorphism. Microbiol Rev. 1991 Jun;55(2):234-58. PMID 1886520; PMCID: PMC372813.
- ↑ 5.0 5.1 Skiada A, Lass-Floerl C, Klimko N, Ibrahim A, Roilides E, Petrikkos G. Challenges in the diagnosis and treatment of mucormycosis. Med Mycol. 2018 Apr 1;56(suppl_1):93-101. doi: 10.1093/mmy/myx101. PMID 29538730; PMCID: PMC6251532.
- ↑ Gryganskyi AP, Golan J, Dolatabadi S, Mondo S, Robb S, Idnurm A, Muszewska A, Steczkiewicz K, Masonjones S, Liao HL, Gajdeczka MT, Anike F, Vuek A, Anishchenko IM, Voigt K, de Hoog GS, Smith ME, Heitman J, Vilgalys R, Stajich JE. Phylogenetic and Phylogenomic Definition of Rhizopus Species. G3 (Bethesda). 2018 May 31;8(6):2007-2018. doi: 10.1534/g3.118.200235. Erratum in: G3 (Bethesda). 2019 Aug 8;9(8):2789. PMID 29674435; PMCID: PMC5982828.
- ↑ 7.0 7.1 Nagao K, Ota T, Tanikawa A, Takae Y, Mori T, Udagawa S, Nishikawa T. Genetic identification and detection of human pathogenic Rhizopus species, a major mucormycosis agent, by multiplex PCR based on internal transcribed spacer region of rRNA gene. J Dermatol Sci. 2005 Jul;39(1):23-31. doi: 10.1016/j.jdermsci.2005.01.010. Epub 2005 Feb 25. PMID 15978416.
- ↑ Compain F, Aït-Ammar N, Botterel F, Gibault L, Le Pimpec Barthes F, Dannaoui E. Fatal Pulmonary Mucormycosis due to Rhizopus homothallicus. Mycopathologia. 2017 Oct;182(9-10):907-913. doi: 10.1007/s11046-017-0151-7. Epub 2017 Jun 3. PMID 28580534.
- ↑ Morales-Aguirre JJ, Agüero-Echeverría WM, Ornelas-Carsolio ME, Reséndiz-Sánchez J, Gómez-Barreto D, Cashat-Cruz M. Successful treatment of a primary cutaneous zygomycosis caused by Absidia corymbifera in a premature newborn. Pediatr Infect Dis J. 2004 May;23(5):470-2. doi: 10.1097/01.inf.0000122612.42982.7c. PMID 15131477.
- ↑ Constantinides J, Misra A, Nassab R, Wilson Y. Absidia corymbifera fungal infection in burns: a case report and review of the literature. J Burn Care Res. 2008 Mar-Apr;29(2):416-9. doi: 10.1097/BCR.0b013e318166da78. PMID 18354306.
- ↑ Rodríguez-Lobato E, Ramírez-Hobak L, Aquino-Matus JE, Ramírez-Hinojosa JP, Lozano-Fernández VH, Xicohtencatl-Cortes J, Hernández-Castro R, Arenas R. Primary Cutaneous Mucormycosis Caused by Rhizopus oryzae: A Case Report and Review of Literature. Mycopathologia. 2017 Apr;182(3-4):387-392. doi: 10.1007/s11046-016-0084-6. Epub 2016 Nov 3. PMID 27807669.
- ↑ Mattner F, Weissbrodt H, Strueber M. Two case reports: fatal Absidia corymbifera pulmonary tract infection in the first postoperative phase of a lung transplant patient receiving voriconazole prophylaxis, and transient bronchial Absidia corymbifera colonization in a lung transplant patient. Scand J Infect Dis. 2004;36(4):312-4. doi: 10.1080/00365540410019408. PMID 15198193.
- ↑ 13.0 13.1 Li H, Hwang SK, Zhou C, Du J, Zhang J. Gangrenous cutaneous mucormycosis caused by Rhizopus oryzae: a case report and review of primary cutaneous mucormycosis in China over Past 20 years. Mycopathologia. 2013 Aug;176(1-2):123-8. doi: 10.1007/s11046-013-9654-z. Epub 2013 Apr 25. PMID 23615822.
- ↑ Danion F, Aguilar C, Catherinot E, Alanio A, DeWolf S, Lortholary O, Lanternier F. Mucormycosis: New Developments into a Persistently Devastating Infection. Semin Respir Crit Care Med. 2015 Oct;36(5):692-705. doi: 10.1055/s-0035-1562896. Epub 2015 Sep 23. PMID 26398536.
- ↑ Rosenberger RS, West BC, King JW. Survival from sino-orbital mucormycosis due to Rhizopus rhizopodiformis. Am J Med Sci. 1983 Nov-Dec;286(3):25-30. doi: 10.1097/00000441-198311000-00004. PMID 6356916.
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