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Coccidioides immitis

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Title: Coccidioides immitis  
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Subject: Coccidioidomycosis, Coccidioides, List of infectious diseases, Arthroconidium, Lines in the Sand (House)
Collection: Eurotiomycetes, Fungi with Sequenced Genomes
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Coccidioides immitis

Coccidioides immitis
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Onygenales
Family: Onygenaceae
Genus: Coccidioides
Binomial name
Coccidioides immitis
G.W. Stiles
Sputum culture of Coccidioides immitis on Sabouraud's medium, showing white, cottony fungus growth
Microscopic appearance of an old culture of Coccidioides immitis, showing fragmented chlamydospores. This is the infective form of the fungus occurring in nature
Septate hyphae of Coccidioides immitis with 90 degree branching and thick walled barrel shaped arthroconidia alternating with empty cells

Coccidioides immitis is a pathogenic fungus that resides in the soil in certain parts of the southwestern United States, northern Mexico, and a few other areas in the Western Hemisphere.[1]

Contents

  • Epidemiology 1
  • Clinical manifestation 2
  • Treatment 3
    • Azoles 3.1
    • Amphotericin 3.2
    • Duration of therapy and costs 3.3
  • HHS select agents listing 4
  • In popular culture 5
  • References 6
  • External links 7

Epidemiology

C. immitis, along with its relative C. posadasii,[2] is most commonly seen in the desert regions of the southwestern United States, including certain areas of Arizona, California, New Mexico, Nevada, Texas, and Utah; and in Central and South America in Argentina, Brazil, Colombia, Guatemala, Honduras, Mexico, Nicaragua, Paraguay, and Venezuela.[3] C. immitis is largely found in California, while C. posadasii is endemic to Texas, northern Mexico and in Central and South America. Both C. immitis and C. posadasii are present in Arizona.[4]

Clinical manifestation

C. immitis can cause a disease called

  • Identification of Coccidioides immitis and Coccidioides posadasii, a presentation by Nancy L Wengenack, PhD, Director of the Mycology and Mycobacteriology Laboratories and Associate Professor of Laboratory Medicine and Pathology in the Division of Clinical Microbiology at Mayo Clinic

External links

  1. ^ a b c
  2. ^
  3. ^
  4. ^ Hospenthal, Duane R., and Michael G. Rinaldi. Diagnosis and Treatment of Human Mycoses. Totowa, N.J.: Humana Press, 2007, p. 296-297.
  5. ^
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References


Coccidioides immitis is used as a plot device in Thunderhead, a novel by Douglas Preston and Lincoln Child. The fungus (prepared from infected victims) is revealed to be the principal agent in corpse powder (based on corpse poison used by Witch). It was also mentioned by the fictional antihero Dr. Gregory House (played by actor Hugh Laurie) on the Television Series, House MD (episode Lines in the Sand).

In popular culture

Along with C. posadasii, C. immitis was featured on the select agents and toxins list compiled by the U.S. Department of Health and Human Services (HHS), as evident from the Code of Federal Regulations (42 CFR 73).[11] However, on October 5, 2012 due to advances in medical research and development of a number of licensed treatments, both pathogens were removed from the HHS select agents listing.[12]

HHS select agents listing

The cost of antifungal therapy is high, from $5,000 to $20,000 per year. These costs increase for critical patients in need of intensive care. Arizona spent an average of $33,762 per patient with coccidioidomycosis between 1998 and 2001.

The objectives of treatment are resolution of infection, decrease of antibody titers, return of function of involved organs, and prevention of relapse. The duration of therapy is dictated by the clinical course of the illness, but it should be at least 6 months in all patients and often a year or longer in others. Therapy is tailored based on a combination of resolution of symptoms, regression of radiographic abnormalities, and changes in CF IgG titers. Immunocompromised patients and patients with a history of meningeal involvement require lifelong treatment.

Duration of therapy and costs

Amphotericin B, introduced in 1957, remains the treatment of choice for severe infections. It is usually reserved for worsening disease or lesions located in vital organs such as the spine. It can be administered either in the classic amphotericin B deoxycholate formulation or as a lipid formulation. No studies have directly compared amphotericin B with azole therapy. Complications include renal toxicity, bone marrow toxicity, and local systemic effects (fever, rigors).

Amphotericin

Several case reports have studied caspofungin, with differing results. Caspofungin 50 mg/day following administration of amphotericin B in a patient with acute pulmonary coccidioidomycosis who had undergone transplantation showed promising results. In a patient with disseminated coccidioidomycosis, first-line therapy with amphotericin B and caspofungin alone failed to elicit a response, but the patient was then given caspofungin combined with fluconazole, with good results. A published report described a patient with disseminated and meningeal coccidioidomycosis in whom conventional therapy with fluconazole, voriconazole, and amphotericin B failed; caspofungin 50 mg/day after a loading dose of 70 mg intravenously was also unsuccessful.

Posaconazole has been approved by the European Commission as a salvage therapy for refractory coccidioidomycosis. Clinical trials are now ongoing for further evaluation. Voriconazole is also being studied in salvage therapy for refractory cases. A case report indicated that voriconazole in combination with amphotericin B as salvage therapy for disseminated coccidioidomycosis was successful.

In very severe cases, combination therapy with amphotericin B and an azole have been postulated, although no trials have been conducted. Caspofungin in combination with fluconazole has been cited as beneficial in a case report of a 31-year-old Asian patient with coccidioidal pneumonia. In a case report of a 23-year-old Black male with HIV and coccidioidal meningitis, combination therapy of amphotericin B and posaconazole led to clinical improvement.

For patients who are unresponsive to fluconazole, options are limited. Several case reports have studied the efficacy of three newer antifungal agents in the treatment of disease that is refractory to first-line therapy: posaconazole and voriconazole (triazole compounds similar in structure to fluconazole) and caspofungin (glucan synthesis inhibitor of the echinocandin structural class). However, these drugs have not been FDA approved, and clinical trials are lacking. Susceptibility testing of Coccidioides species in one report revealed uniform susceptibility to most antifungal agents, including these newer drugs.

Of the azoles, ketoconazole is the only one approved by the U.S. Food and Drug Administration (FDA) for treatment of coccidioidomycosis. Nevertheless, although it was initially used in the long-term treatment of nonmeningeal extrapulmonary disease, more-potent, less-toxic triazoles (fluconazole and itraconazole) have replaced it. Itraconazole (400 mg/day) appears to have efficacy equal to that of fluconazole in the treatment of nonmeningeal infection and have the same relapse rate after therapy is discontinued. However, itraconazole seems to perform better in skeletal lesions, whereas fluconazole performs better in pulmonary and soft tissue infection. Serum levels of itraconazole are commonly obtained at the onset of long-term therapy because its absorption is sometimes erratic and unpredictable. Complications can include hepatic dysfunction.

The introduction of azoles revolutionized treatment for coccidioidomycosis,[10] and these agents are usually the first line of therapy. However, none of the azoles is safe to use in pregnancy and lactation because they have shown teratogenicity in animal studies.

Azoles

  • Risk factors for dissemination (for which treatment should be initiated):
    • Primary infection during infancy
    • Primary infection during pregnancy, especially in the third trimester or immediately post partum
    • Immunosuppression (e.g., patients with HIV/AIDS, transplant recipients, patients receiving high-dose corticosteroids, those receiving antitumor necrosis factor medications)
    • Chronic debilitation or underlying disease, including diabetes mellitus or preexisting cardiopulmonary disease
    • High inoculum exposures
    • Certain ethnicities, such as Filipino, Black, or Hispanic
    • Age greater than 55 years
  • Commonly used indicators to judge the severity of illness include:[9]
    • Continuous fever for longer than 1 month
    • Body-weight loss of more than 10%
    • Intense night sweats that persist for more than 3 weeks
    • Infiltrates that involve more than half of one lung or portions of both lungs
    • Prominent or persistent hilar adenopathy
    • Anticoccidioidal complement fixation IgG titers of 1:16 or higher
    • Absence of dermal hypersensitivity to coccidioidal antigens
    • Inability to work
    • Symptoms that persist for more than 2 months
  • Most Coccidioides infections have an incubation period from one to four weeks[1] and resolve without specific therapy; few clinical trials have assessed outcomes in less-severe disease.

Treatment

pathogen. biosafety level 3, and was considered a U.S. Department of Agriculture and the U.S. Department of Health and Human Services by both the select agent had been listed as a C. immitis Until October 2012, [1] It is reported as the tenth-most often acquired infection in the laboratory conditions with two documented deaths.[8]

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