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Opportunistic Mycoses (, , ) Immunology/ > Microbiology of Fungi > Microbiology of Fungi

OPPORTUNISTIC MYCOSES

Conditions that favor Opportunistic Mycoses: Recall that "opportunistic" are micro-organisms that are commonly found in the environment, even our own microbiomes, that cause when the "opportunity" arises – for example, in immunosuppressed individuals or when trauma permits access to a novel niche within the body.

• The fungi responsible for opportunistic mycoses cause disease when normal host defenses are impaired.

• Thus, populations with increased risk of infection include the following:

– Patients with , especially due to: Underlying disease, such as HIV infection, hematological malignancies, or mellitus; Immune suppressing treatments, such as , organ transplants, and ; Additionally, the very young and elderly are more vulnerable. – Then, denote that some patients are at risk due to increased exposure to the fungi: For example, hospital settings, surgery, and medical devices or implants increase risk of infection.

• Be aware that, as the number of people living with immunosuppressive disorders and therapies has increased, so, too, has the frequency of opportunistic mycoses.

• Recent research indicates a possible link between host genetics and susceptibility to opportunistic .

Candidiasis: The most common opportunistic . Caused by species of , especially * – Other important species include C. glabrata, C. parapsilosis, C. tropicalis, and C. krusei. Candida are thermally dimorphic:* – They exist as budding and pseudohyphae at 20 degrees Celsius, and form germ tubes at 37 degrees Celsius. – In the third image in the diagram, we can see a Candida albicans colony that comprises yeast-like cells with filamentous cells on top. Candida are commonly found in our gastrointestinal and urogenital tracts, and on the *. – Thus, most infections are endogenous. – Exogenous infections are less common, but are more likely in health care settings. Candidiasis can manifest in several forms throughout the body; we'll organize in terms of superficial and invasive infections. Superficial candidiasis is the result of localized overgrowth.

• On mucosal surfaces, overgrowth is visible as whitish plaques and pseudomembranes;

• On the skin, overgrowth produces erythematous and/or vesiculopustular lesions.

• Mucosal and cutaneous forms are typically easy to treat.

• Chronic muco-cutaneous candidiasis is rare, but difficult to treat.

– It is the result of T-lymphocyte defects. Examples of common mucosal and cutaneous candidiasis. Oropharyngeal overgrowth can produce thrush,* which manifests as whitish plaques or pseudomembranes over the palate, buccal surfaces, and tongue. – These lesions are generally painless, though they can cause a "cottony" feeling in the mouth and loss of taste. – Oropharyngeal candidiasis can also produce angular cheilitis, which are painful fissures at the

1 / 4 corners of the mouth. – Adults who wear dentures can develop a form of , called denture stomatitis, which is characterized by uncomfortable erythema without plaques.

• produces plaques or pseudomembranes in the esophagus, and produces pain upon swallowing (odynophagia); this is most common in HIV patients with low CD4+ T-cell counts (thus, it is an AIDS-defining illness).

• Intra-abdominal overgrowth is associated with hospitalized patients, especially those who have had abdominal surgery.

– Infection can involve the peritoneum and/or any of the abdominal viscera.

• Cutaneous candidiasis tends to occur in the body folds, where conditions are warm and moist, such as the armpits, under the breasts, and groin area.

– The red is often itchy, and can become painful. Diaper rash can also be caused by Candida* overgrowth; the red, itchy rash tends to appear in the folds of the groin, buttocks, and external genitalia.

• Vulvovaginal candidiasis (aka, vaginal yeast infections) is characterized by whitish plaques, itching, and a foul- smelling discharge.

•

Occurs as the result of hematological dissemination or trauma that introduces fungi to a novel site.

• Infection can be focal, for example, localized within the heart, , brain, bones, or other organ system, or, can be systemic.

• Candidemia and dissemination to the viscera is more likely in neutropenic and hospitalized patients.

Candida* species are major causes of central-line associated . Cryptococcosis: Infections of the CNS and pulmonary system caused by neoformans and .

• These fungi are found in bird droppings, and, by association, soil and trees.

• They are encapsulated, spherical yeast

– Outer "halo" is the polysaccharide capsule – Inner yeast cell has melanin in its . Cryptococcus* is inhaled into the respiratory system, followed by dissemination to and localization within the CNS. is a major opportunistic in AIDS patients.*

• Cryptococcosis typically manifests as CNS infections:

– and encephalitis – In the image, we can see the characteristic "soap bubble" lesions of Cryptococcal encephalitis. Cryptococcus neoformans* CNS infection is associated with immunosuppressed patients

• Cryptococcus gattii tend to produce infection in relatively immunocompetent individuals

– These patients tend to have more formation – Some authors suggest that so-called immunocompetent patients actually have complicating illnesses or histories of immunosuppression.

• Cryptococcosis can also manifest as pulmonary infection, sometimes following CNS involvement.

– In the lungs, severity ranges from asymptomatic to with pulmonary infiltrates. – Cryptococcus gattii tends to produce larger pulmonary lesions than Cryptococcus neoformans. Aspergillosis Caused by species of , especially – Additional important species include A. flavus, A.

2 / 4 niger, and A. terreus. Aspergillus* forms hyaline with abundant conidia production. – Conidia are the asexual that are ubiquitous in our environment, both outside and inside, including hospitals. – We are constantly inhaling these spores, which, in the immunocompetent, are typically harmless.

• Spores can colonize and/or invade individuals who have immune abnormalities.

• Hypersensitivity, i.e., allergic reactions to Aspergillus:*

Allergic Aspergillus * is a form of chronic rhinosinusitis that can obstruct the sinuses and produce asymmetrical swelling around the orbit and/or nasal sinuses.

• Allergic bronchopulmonary aspergillosis occurs in patients with and .

– In these individuals, the fungi colonize the bronchopulmonary tissue. – This can lead to obstruction or, upon damage to the vasculature, hemoptysis (coughing up blood).

• Because allergic sinusitis and bronchopulmonary aspergillosis are the result of hypersensitivity reactions, corticosteroids are often recommended.

Underlying chronic pulmonary illnesses and/or immunosuppression Aspergillosis can take a variety of forms:

• Aspergillomas, aka, balls (or mycetomas), can form within pre-existing cavities within the lungs or sinuses.

– For example, in a patient with a history of , fungal balls can form within cavities produced by TB infection. – These masses comprise fungal hyphae as well as tissue debris and inflammatory cells.

• Chronic pulmonary aspergillosis occurs in patients with chronic disease.

– In these individuals, localized lung tissue invasion occurs, which can lead to cavitation with or without formation of fungal balls, or even fibrosis.

• Invasive aspergillosis occurs in patients with severe , and, because of the invasive nature, has a high mortality rate.

– In addition to pulmonary tissue invasion and destruction, the fungus may disseminate to other organs and cause invasive damage.

• Aspergillosis can also be a cutaneous mycosis, typically following a .

Learn about Mucormycoses

REFERENCES

"Allergic Bronchopulmonary Aspergillosis | AAAAI." The American Academy of , Asthma & Immunology. Accessed October 18, 2018. https://www.aaaai.org/conditions-and-treatments/related-conditions/allergic- bronchopulmonary-aspergillosis. Azim, Afzal, Armin Ahmed, Arvind Kumar Baronia, Rungmei S K Marak, and Nabeel Muzzafar. "INTRA-ABDOMINAL CANDIDIASIS," n.d., 10. Bassetti, Matteo, Elda Righi, Filippo Ansaldi, Maria Merelli, Claudio Scarparo, Massimo Antonelli, Jose Garnacho-Montero, et al. "A Multicenter Multinational Study of Abdominal Candidiasis: Epidemiology, Outcomes and Predictors of Mortality." Intensive Care Medicine 41, no. 9 (September 1, 2015): 1601–10. https://doi.org/10.1007/s00134-015-3866-2. "Chronic Pulmonary Aspergillosis (CPA) and | Aspergillus & Aspergillosis Website." Accessed October 18, 2018. https://www.aspergillus.org.uk/content/chronic- pulmonary-aspergillosis-cpa-and-aspergilloma-0. "Opportunistic Systemic Mycoses | Online." Accessed October 15, 2018. https://mycology.adelaide.edu.au/mycoses/opportunistic/. Fanucci, E., M. Nezzo, L. Neroni, L. Montesani, L. Ottria, and M. Gargari. "Diagnosis and Treatment of Paranasal Sinus Fungus Ball of Odontogenic Origin: Case Report." Oral & Implantology 6, no. 3 (April 4, 2014): 63–66. "Invasive Pulmonary Aspergillosis – Case Report and Review of Literature." Accessed October 18, 2018. https://www-ncbi-nlm-nih-

3 / 4 gov.proxy.medlib.uits.iu.edu/pmc/articles/PMC4318821/. Johannson, Kerri A., Shaunna M. Huston, Christopher H. Mody, and Warren Davidson. "Cryptococcus Gattii Pneumonia." CMAJ : Canadian Medical Association Journal 184, no. 12 (September 4, 2012): 1387–90. https://doi.org/10.1503/cmaj.111346. Kumamoto, Carol A. "Inflammation and Gastrointestinal Candida Colonization." Current Opinion in Microbiology 14, no. 4 (August 2011): 386–91. https://doi.org/10.1016/j.mib.2011.07.015. Kwon-Chung, K. J., J. A. Fraser, T. L. Doering, Z. A. Wang, G. Janbon, A. Idnurm, and Y.-S. Bahn. "Cryptococcus Neoformans and Cryptococcus Gattii, the Etiologic Agents of Cryptococcosis." Cold Spring Harbor Perspectives in Medicine 4, no. 7 (July 1, 2014): a019760–a019760. https://doi.org/10.1101/cshperspect.a019760. May, Robin C., Neil R.H. Stone, Darin L. Wiesner, Tihana Bicanic, and Kirsten Nielsen. "Cryptococcus: From Environmental Saprophyte to Global Pathogen." Nature Reviews. Microbiology 14, no. 2 (February 2016): 106–17. https://doi.org/10.1038/nrmicro.2015.6. McDonald, Tami, Darin L. Wiesner, and Kirsten Nielsen. "Cryptococcus." Current Biology : CB 22, no. 14 (July 24, 2012): R554–55. https://doi.org/10.1016/j.cub.2012.05.040. Murray, P. R., Rosenthal K.S., & Pfaller, M.A. . 8th ed. Elsevier, 2016. Perfect, John R., and Tihana Bicanic. "Cryptococcosis Diagnosis and Treatment: What Do We Know Now." Fungal Genetics and Biology, Cryptococcus: model basidiomycetes and deadly pathogens, 78 (May 1, 2015): 49–54. https://doi.org/10.1016/j.fgb.2014.10.003. "Sources of Aspergillosis | | Aspergillosis | Types of Fungal Diseases | Fungal Diseases | CDC," October 12, 2017. https://www.cdc.gov/fungal/diseases/aspergillosis/causes.html. Underhill, David M., and Iliyan D. Iliev. "The Mycobiota: Interactions between Commensal Fungi and the Host ." Nature Reviews. Immunology 14, no. 6 (June 2014): 405–16. https://doi.org/10.1038/nri3684. Vergidis, Pascalis, Cornelius J. Clancy, Ryan K. Shields, Seo Young Park, Brett N. Wildfeuer, Richard L. Simmons, and M. Hong Nguyen. "Intra-Abdominal Candidiasis: The Importance of Early Source Control and Treatment." PLOS ONE 11, no. 4 (April 28, 2016): e0153247. https://doi.org/10.1371/journal.pone.0153247. Yapar, Nur. "Epidemiology and Risk Factors for Invasive Candidiasis." Therapeutics and Clinical Risk Management 10 (February 13, 2014): 95–105. https://doi.org/10.2147/TCRM.S40160. Images: "Aspergilloma." Wikipedia, October 5, 2018. https://en.wikipedia.org/w/index.php?title=Aspergilloma&oldid=862535653. "Sources of Aspergillosis | | Aspergillosis | Types of Fungal Diseases | Fungal Diseases | CDC," October 12, 2017. https://www.cdc.gov/fungal/diseases/aspergillosis/causes.html. "C. Albicans Hyphal Mass." Wikipedia, October 13, 2018. https://en.wikipedia.org/w/index.php?title=Candida_albicans&oldid=863856627. Cryptococcosis of Lung in Patient with AIDS. Mucicarmine Stain. 1984. https://commons.wikimedia.org/wiki/File:Cryptococcosis_of_lung_in_patient_with_ AIDS._Mucicarmine_stain_962_lores.jpg. Centers for Disease Control and Prevention's Public Health Image Library (PHIL), #3771. This Photomicrograph Depicts Cryptococcus Neoformans Using a Light India Ink Staining Preparation. 1969. https://commons.wikimedia.org/wiki/File:Cryptococcus_neoformans_using_a_light_India_ink_staining_preparation _PHIL_3771_lores.jpg. "Centers for Disease Control and Prevention's Public Health Image Library (PHIL), #1217. Thrush Candida albicans. PHIL 1217 lores.jpg." . Accessed October 18, 2018. https://sr.wikipedia.org/sr-el/%D0%94%D 0%B0%D1%82%D0%BE%D1%82%D0%B5%D0%BA%D0%B0:Oral_thrush_Aphthae_Candida_albicans._PHIL_1217_l ores.jpg. "File:Esophageal Candidiasis.Jpg." Wikipedia, December 30, 2011. endoscopic image of esophageal candidiasis, seen on endoscopy of a patient after chemotherapy. Posted under GFDL on permission of patient https://en.wikipedia.org/w/index.php?title=File:Esophageal_candidiasis.jpg&oldid=468437436. Garnhami. "C. Albicans Colony." Wikipedia, October 13, 2018. https://en.wikipedia.org/w/index.php?title=Candida_albicans&oldid=863856627. KGH. Esophageal Candidiasis Stained by Periodic Acid-Schiff Procedure. December 4, 2005. Personal collection of histopathologic slides. https://commons.wikimedia.org/wiki/File:Esophageal_candidiasis_(2)_PAS_stain.jpg. Zordan, R.E., Miller, M.G., Galgoczy, B.B. T., and Johnson, A.D. "C. Albicans Cells." Wikipedia, October 13, 2018. https://en.wikipedia.org/w/index.php?title=Candida_albicans&oldid=863856627.

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