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Recombinant DNA Cut And Tape Classroom Activity

Respiratory Mycoses

Learning Objectives











a) Large, dark lesions on a face. B) A microrgraph of spheres in a larger sphere.

John’s negative RIDT tests do not rule out influenza, since false-negative results are common, but the Legionella infection still must be treated with antibiotic therapy and is the more serious condition. John's prognosis is good, provided the physician can find an antibiotic therapy to which the infection responds.

While John was undergoing treatment, three of the employees from the home improvement store also reported to the clinic with very similar symptoms. All three were older than 55 years and had Legionella antigen in their urine; L. pneumophila was also isolated from their sputum. A team from the health department was sent to the home improvement store to identify a probable source for these infections. Their investigation revealed that about 3 weeks earlier, the store's air conditioning system, which was located where the employees ate lunch, had been undergoing maintenance. L. pneumophila was isolated from the cooling coils of the air conditioning system and intracellular L. pneumophila was observed in amoebae in samples of condensed water from the cooling coils as well ([link]). The amoebae provide protection for the Legionella bacteria and are known to enhance their pathogenicity.3

In the wake of the infections, the store ordered a comprehensive cleaning of the air conditioning system and implemented a regular maintenance program to prevent the growth of biofilms within the cooling tower. They also reviewed practices at their other facilities.

After a month of rest at home, John recovered from his infection enough to return to work, as did the other three employees of the store. However, John experienced lethargy and joint pain for more than a year after his treatment.


Go back to the previous Clinical Focus box.


Blastomycosis is a rare disease caused by another dimorphic fungus, Blastomyces dermatitidis. Like Histoplasma and Coccidioides, Blastomyces uses the soil as a reservoir, and fungal spores can be inhaled from disturbed soil. The pulmonary form of blastomycosis generally causes mild flu-like symptoms and is self-limiting. It can, however, become disseminated in immunocompromised people, leading to chronic cutaneous disease with subcutaneous lesions on the face and hands ([link]). These skin lesions eventually become crusty and discolored and can result in deforming scars. Systemic blastomycosis is rare, but if left untreated, it is always fatal.


a) Large crusty legions on a deformed hand. B) A micrograph of round cells.


A variety of fungi in the order Mucorales cause mucormycosis, a rare fungal disease. These include bread molds, like Rhizopus and Mucor; the most commonly associated species is Rhizopus arrhizus (oryzae) (see [link]). These fungi can colonize many different tissues in immunocompromised patients, but often infect the skin, sinuses, or the lungs.







An X ray showing white bones on a black background. White webbing in the upper lung is circled.

Pneumocystis Pneumonia


Micrograph of dark purple circles on a light purple background.




a) A micrograph with dark circles (some attached to form a figure 8) on a green background. The dark cells are labeled Cryptococcus. The figure 8 cells are labeled budding cells. b) a negative stain micrograph of cryptococcus neoformans is shown. It appears as green spots on a brown background.
Fungal Diseases of the Respiratory Tract


Table titled: Fungal Infections of the Respiratory Tract. Columns: Disease, Pathogen, Signs and Symptoms, Diagnostic Tests, Antimicrobial Drugs. Aspergillosis; Aspergillus fumigatus; Shortness of breath, wheezing, coughing, runny nose, headaches; formation of aspergillomas causing severe pneumonia and pulmonary or brain hemorrhages; can be fatal; Chest radiograph, skin test, microscopic observation of sputum samples; Itraconazole, voriconazole. Blastomycosis; Blastomyces dermatitidis; Fever, chills, cough, headache, fatigue, chest pain, body aches; in disseminated infections, chronic, crusted lesions on face and hands with permanent scarring; can be fatal; Microscopic observation of sputum samples; urine antigen test; EIA; Amphotericin B, ketoconazole; Coccidioidomycosis (Valley fever); Coccidioides immitis; Granulomatous lesions on face and nose; may spread to organs or brain, causing fatal meningitis; Culture (in BSL-3 lab only), serological antibody tests; Amphotericin B. Cryptococcosis; Cryptococcus neoformans; Fever, cough, shortness of breath; can cause fatal meningitis if disseminated to brain; Microscopic examination of lung tissue or cerebrospinal fluid; Amphotericin B, fluconazole, flucytosine. Histoplasmosis; Histoplasma capsulatum; Fever, headache, weakness, chest pain, lesions on lungs; Chest radiograph, culture, direct fluorescence antibody staining, complement fixation assay, histoplasmin sensitivity test Amphotericin B, ketoconazole, itraconazole. Mucormycosis; Rhizopus arrhizus, other Rhizopus spp., Mucor spp.; Headache, fever, facial swelling, congestion, black lesions in oral cavity, cough, chest pain, shortness of breath; often fatal; Microscopic examination of tissue biopsy specimens; Amphotericin B. Pneumocystis pneumonia (PCP); Pneumocystis jirovecii Fever, cough, shortness of breath; can be fatal if untreated Microscopic examination of lung tissue and fluid, PCR; Trimethoprim-sulfamethoxazole.

Key Concepts and Summary

Multiple Choice

Which of these infections is also referred to as Valley fever?

  1. histoplasmosis
  2. coccidioidomycosis
  3. blastomycosis
  4. aspergillosis


Which of the following is not caused by a dimorphic fungus?

  1. histoplasmosis
  2. coccidioidomycosis
  3. blastomycosis
  4. aspergillosis


Which of the following is caused by infections by bread molds?

  1. mucormycosis
  2. coccidioidomycosis
  3. cryptococcosis
  4. Pneumocystis pneumonia


In the United States, most histoplasmosis cases occur

  1. in the Pacific northwest.
  2. in the desert southwest.
  3. in the Mississippi river valley.
  4. in Colorado river valley.


Which of the following infections can be diagnosed using a skin test similar to the tuberculin test?

  1. histoplasmosis
  2. cryptococcosis
  3. blastomycosis
  4. aspergillosis


Fill in the Blank

In coccidioidomycosis, _______ containing many endospores form in the lungs.


In cryptococcosis, the main fungal virulence factor is the _______, which helps the pathogen avoid phagocytosis.


In some mycoses, fungal balls called _______ form in the lungs


Most US cases of coccidioidomycosis occur in _______.

the desert southwest

Coccidioidomycosis may develop when Coccidioides immitis _______ are inhaled.


Short Answer

Which pulmonary fungal infection is most likely to be confused with tuberculosis? How can we discriminate between these two types of infection?

Compare and contrast aspergillosis and mucormycosis.

Critical Thinking

Why are fungal pulmonary infections rarely transmissible from person to person?


  1. 1 NE Manos et al. “Geographic Variation in the Prevalence of Histoplasmin Sensitivity.” Dis Chest 29, no. 6 (1956):649–668.
  2. 2 DR Hospenthal. “Coccioidomycosis.” Medscape. 2015. http://emedicine.medscape.com/article/215978-overview. Accessed July 7, 2016.
  3. 3 HY Lau and NJ Ashbolt. “The Role of Biofilms and Protozoa in Legionella Pathogenesis: Implications for Drinking Water.” Journal of Applied Microbiology 107 no. 2 (2009):368–378.
  4. 4 Centers for Disease Control and Prevention. “Fungal Diseases. Definition of Mucormycosis.” 2015 http://www.cdc.gov/fungal/diseases/mucormycosis/definition.html. Accessed July 7, 2016.
  5. 5 Centers for Disease Control and Prevention. “Fungal Diseases. Symptoms of Mucormycosis.” 2015 http://www.cdc.gov/fungal/diseases/mucormycosis/symptoms.html. Accessed July 7, 2016.
  6. 6 MM Roden et al. “Epidemiology and Outcome of Zygomycosis: A Review of 929 Reported Cases.” Clinical Infectious Diseases 41 no. 5 (2005):634–653.



© 2009-2016 Anthony D'Onofrio, PhD