Fungal Infections in Humans

Author: Timothy Walls, M.D., M.S.
Reviewer: Julie Ann West, PhD (CPH [NBPHE]), MLS(ASCP)CMSM(ASCP)CM and Joshua J. Cannon, MS, MLS(ASCP)CMSHCM
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Continuing Education Credits

P.A.C.E.® Contact Hours: 2 hour(s)

Florida Board of Clinical Laboratory Science CE Credit Hours

Florida Board of Clinical Laboratory Science CE - General (Microbiology/Mycology/Parasitology): 2 hour(s)

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Upon completion of the course, the reader will have accomplished several skills: recognize the geographic distribution and anatomical predilection of the primary fungi causing human disease, recognize the clinical manifestation of disease, and identify pathogenic fungi through their unique distinguishing features such as culture growth characteristics and morphology.

Objectives

  • Discuss safety considerations, taxonomy, and importance (clinical manifestations) of medically important fungi.
  • Describe, recognize, and identify yeast associated with infections in humans.
  • Describe, recognize, and identify molds associated with infections in humans.
  • Describe, recognize, and identify dimorphic fungi associated with infections in humans.
  • State the current and emerging techniques for the diagnosis of mycotic infection.

Course Outline

  • Introduction to Medically Important Fungi
    • Introduction to Yeast, Molds, Thermally Dimorphic Fungi, and Safety Considerations
    • Taxonomy
    • Clinical Manifestations
    • The taxonomy of fungi is constantly evolving. One such reason for this is:
  • Yeast: Describe, Recognize, and Identify
    • Yeast
    • Introduction to Cryptococcus
    • Cryptococcus Epidemiology
    • Cryptococcal Infections
    • Cryptococcus Identification
    • All of the following special microbiology/histology stains are useful for the identification of Cryptococcus, except:
    • True or False: Cryptococcus is commonly found in soil contaminated by bird droppings, decaying wood, and tree hollows.
    • Candida species
    • Candida glabrata
    • Which feature distinguishes Candida glabrata from other infectious Candida species?
    • Rhodotorula
    • True or False: Rhodotorula species are yeasts that produce a pyocyanin pigment ranging from yellowish to red, which can be visualized in individual colonies.
    • Malassezia
    • Which supplement is necessary to add to culture media to ensure proper growth of Malassezia species?
    • Saccharomyces cerevisiae
    • Trichosporon
    • Trichosporon, continued
    • True or False: Trichosporon yeasts form arthroconidia and hyphal elements that are larger than those of Candida species.
    • Blastoschizomyces
    • Pneumocystis: The "Yeast-like" Fungus
  • Molds: Describe, Recognize, and Identify...
    • Molds
  • Aspergillus
    • Aspergillus
    • Aspergillus, continued
    • Aspergillus niger
    • What is a distinguishing feature of Aspergillus species as seen in stains of tissues?
  • Fusarium
    • Fusarium
    • What shape is commonly associated with the description of the macroconidia of Fusarium species?
  • Dermatophytes
    • Introduction to Dermatophytes
    • Which enzymes do dermatophytes employ to digest hair, nails, and the stratum corneum of skin?
    • Epidermophyton
    • True or False: Epidermophyton floccosum always produces microconidia.
    • Which antibiotic is used in growth media to help isolate dermatophytes?
    • Trichophyton
    • Trichophyton, continued
    • Microsporum
    • Microsporum, continued
    • The dermatophytes consist of all of the following, except:
  • Dematiaceous Molds
    • Introduction to Dematiaceous Molds
    • Dematiaceous Molds, continued
    • True or False: Typically, dematiaceous molds are darkly pigmented on the culture plate's surface and reverse side.
    • Which is a feature that can differentiate rapidly growing dematiaceous molds?
    • Alternaria
    • Scedosporium
    • True or False: Upon culture, Lomentospora prolificans mold has a gray or black surface and reverse; the annellides have swollen bases and thin necks.
  • Mucormycetes
    • Introduction to Mucormycetes
    • Mucormycetes, continued
    • If Mucormycosis (previously called zygomycosis) is clinically suspected, then how should a tissue specimen be prepared prior to culture?
    • True or False: The Mucor species do not produce rhizoids.
  • Dimorphic Fungi: Describe, Recognize, and Identify
    • Dimorphic Fungi
    • Characteristics of Dimorphic Fungi
    • True or False: The thermally dimorphic fungi grow as yeast when incubated at 25° C but grow as molds when incubated at 30° or 37° C.
    • Coccidioides
    • True or False: Arthroconidia of Coccidioides spp. are oval-shaped and alternate with empty cells.
    • Coccidioides, continued
    • In addition to culture, diagnosis of coccidioidomycosis can be accomplished by which of the following?
    • Paracoccidioides brasiliensis
    • True or False: Paracoccidioides brasiliensis appears like a mariner's wheel in tissue sections or primary wet preparations.
    • Paracoccidioides brasiliensis, continued
    • Blastomyces
    • Blastomyces, continued
    • What characteristic budding morphology can help identify Blastomyces species?
    • True or False: Diagnosis of blastomycosis can be made with an antigen test performed on urine or serum.
    • Histoplasma
    • Which cells are H. capsulatum yeast cells often found within?
    • Histoplasmosis
    • Sporothrix schenckii
    • True or False: Microscopically, the S. schenckii mold produces very delicate hyaline septate hyphae, which produce conidiophores topped by clusters of macroconidia ("rosettes").
    • Talaromyces marneffei
    • How do T. marneffei yeast-forms replicate?
  • Current and Emerging Techniques for the Diagnosis of Mycotic Infection
    • Molecular and MALDI Identification Techniques
    • One important limitation to the identification of medically important fungi using the MALDI method is:
  • References
    • References

Additional Information

Level of Instruction: Intermediate 
Intended audience:  Medical laboratory scientists, medical laboratory technicians, laboratory supervisors, and laboratory managers. This course is also appropriate for MLS and MLT students and pathology residents.
Author Information: Timothy Walls, M.D., M.S., is an AP/CP-boarded pathologist. He has completed fellowships in medical microbiology as well as molecular genetic pathology. Currently, he is the Director of Clinical Laboratories at Sentara Reference Laboratories. Timothy has earned his B.S. in Biochemistry, Cellular and Molecular Biology at the University of Tennessee, his M.S. in Forensic Science at Drexel University, and an M.D. from the University of Tennessee Health Science Center.
The author has no conflict of interest to disclose.  
Reviewer Information:
Dr. Julie Ann West is certified by the American Society for Clinical Pathology (ASCP) as a Medical Laboratory Scientist (MLS) and as a Specialist in Microbiology (SM). In addition, Dr. West has earned a Ph.D. in Public Health - Infectious Disease Epidemiology - and is Certified in Public Health (CPH) by the National Board of Public Health Examiners. Dr. West is experienced as a Technical Specialist, Safety Officer, Educator, and Lead in the Veterans Administration Healthcare System and has prior experience as an Administrator.
Joshua J. Cannon, MS, MLS(ASCP)CMSHCM received his Bachelor of Science and Master of Science in Medical Laboratory Science from Thomas Jefferson University in Philadelphia, PA. He holds Medical Laboratory Scientist and Specialist in Hematology certifications through the ASCP Board of Certification. He was a professor at Thomas Jefferson University for seven years before transitioning into his current role as Education Developer at MediaLab by Vastian. His areas of expertise and professional passions include clinical hematology and interprofessional education.