Mycology: Hyaline and Dematiaceous Fungi

Authors: Elmer W. Koneman, MD and Margaret Reinhart, MS, MT(ASCP)
Reviewer: Judi Bennett, BSM, MLS
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Continuing Education Credits

P.A.C.E.® Contact Hours: 1.5 hour(s)

Florida Board of Clinical Laboratory Science CE Credit Hours

Florida Board of Clinical Laboratory Science CE - General (Microbiology/Mycology/Parasitology): 1.5 hour(s)

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Mycology: Hyaline and Dematiaceous Fungi uses an interrogative, question-and-answer, approach to direct and instruct the participant in identifying hyaline and dematiaceous fungi. Numerous images enhance the descriptions of identifying characteristics by illustrating the appearance of fungal colonies on media and microscopic appearance. The course also identifies sources of infection and associated diseases. This course is appropriate for laboratory professionals and students in clinical laboratory science programs who want to increase their understanding of mycology including microscopic and colony appearance and isolate identification.

Objectives

  • Identify hyaline mold isolates by observing the appearance of the colony on agar plates and through microscopic appearance.
  • Discuss various sources of fungal infections and the diseases that are associated with hyaline and dematiaceous molds.
  • Define these terms that apply to fungi and are used to identify specific species: sporulation, conidia, conidiophore, hyphae, phialide.
  • Identify dematiaceous molds by observing characteristic structures and their rate of growth.
  • Identify the common environmental sources (natural habitats) of certain hyaline and dematiaceous molds.
  • Discuss some of the types of diseases associated with opportunistic infections by some of the hyaline and dematiaceous molds.

Course Outline

  • Introduction
    • Introduction
    • Clinical Classifications
    • Pathogens vs. Opportunists
    • Morphological Classifications
    • What are fungi that attack the tissues and organ systems called?
  • Definitions and terms
    • Nomenclature
    • Structures
    • Diseases and Clinical Conditions
    • What is a slow-growing subcutaneous lesion on an extremity that can eventually cause bone deformity called?
  • Hyaline Molds
    • Hyaline Molds
    • The Mucorales (Formerly Zygomycetes)
    • Microscopic Remarks About the Mucorales
    • The Dermatophytes
    • Diagnosis and Identification of Dermatophytes
    • The Opportunistic Mycoses Caused by Other Hyaline Molds
    • Diagnosis and Identification of Opportunistic Mycoses Caused by Other Hyaline Molds
    • Other Notes - Hyaline Molds That Appear Similar to the Mold Phases of Obligate Pathogens
    • Match each hyaline mold from the drop-down list to its corresponding colony and microscopic description. The mold colonies are illustrated in the image on the right.
    • Match each hyaline mold from the drop-down list to its corresponding microscopic and colony description. The microscopic appearance of the molds are illustrated in the image on the right.
    • Match each hyaline mold from the drop-down list to its corresponding colony and microscopic description. The mold colonies are illustrated in the image on the right.
    • Match each of the names of the fungi listed in the left column with its most likely associated disease listed in the right column.
    • Match each of the names of the hyaline molds listed with the environmental conditions or natural objects with which it is most likely associated.
    • Match the names of each of the species of hyaline molds listed with the appropriate category.
    • Match the names of each of the species of hyaline molds listed with the appropriate category.
    • Match the names of each of the species of hyaline molds listed with the appropriate taxonomic category.
    • Match the names of each of the fungi listed below into the appropriate category indicating the classification of infection with which it is most commonly associated.
    • The microscopic features shown in this image are of a fungus commonly associated with which of the following infections?
    • Based on the structures observed in this image, what is the most probable species of the fungus recovered from an induced sputum specimen?
    • Illustrated in this image is a "green lawn" colony of Gliocladium species. What is the other hyaline mold that produces this type of colony?
    • The fungus illustrated in this image was recovered from a single induced sputum specimen (one) from a 74-year-old man with chronic obstructive pulmonary disease (COPD). This isolate is most likely:
    • The dermatophytic fungus shown in this image was recovered from a ringworm lesion of the skin on the back of the hand of an 8-year-old boy. What is the most likely place this fungus originated?
    • An Aspergillus species was recovered from a sputum specimen of a patient with X-ray evidence of fungal pneumonia. Microscopic examination did not permit a species identification. A small amount of vegetative mycelium was removed, and a direct mount was prepared. The features indicated by the red arrows in this image are associated with which Aspergillus species?
    • What is the identification of the hyaline mold shown in this image?
    • The differentiation between Aspergillus species and Scedosporium species may be difficult when only hyphal elements are observed in stained tissue sections. It is important to obtain a culture to make this differentiation when possible because Scedosporium species, in contrast to Aspergillus species, tend to be resistant to which of the following?
    • A dermatophyte that produces thin-walled, two or three-celled macroconidia, and no microconidia, most likely belongs to which genus?
    • The bare fruiting heads shown in this image, characteristic of Aspergillus niger, demonstrate a spherical vesicle with phialides positioned around the entire circumference of the surface. What is the other Aspergillus species that also sporulates circumferentially?
    • A dull white fungus, turning mouse gray on maturity, was recovered from material aspirated from a bone cyst in the upper femur. Based on the microscopic appearance as seen in a lactophenol blue mount of a portion of the colony, what is the most likely identification?
    • The "birds on a fence" arrangement of uniform-sized, tear-shaped microconidia is characteristic of which fungi?
    • The image demonstrates the fruiting heads of Trichoderma species. Note the single, long, tapered phialides (arrow), extending laterally from either side of the hyphae, one of the key identifying features of this fungus. What is another hyaline mold that produces long, tapered phialides?
    • Illustrated here is a single conidium of Microsporum canis. Note that the hilar cell appears fractured (shorter red arrow), where it was released from the stolon. What are macroconidia having this so-called "break-away" cell termed?
    • Which hyaline saprobic fungus has microscopic features similar to the mold form of Histoplasma capsulatum?
    • What is the hyaline saprobic fungus that has microscopic features similar to the mold form of Coccidioides immitis?
    • What is the most helpful feature in differentiating the Mucorales (former Zygomycetes) from the other hyaline molds in the clinical mycology laboratory?
  • Dematiaceous Molds
    • Dematiaceous Molds with Clinical Significance
    • Dematiaceous Molds with Clinical Significance, continued
    • Diagnosis and Identification of Slow-Growing Molds
    • Diagnosis and Identification of Fast-Growing Molds
    • Other Diagnostic Methods for Dematiaceous Molds
    • Match the name of the fungal species listed with the corresponding identifying structures illustrated in the images on the right.
    • Match the name of the fungal species listed with the corresponding identifying structures illustrated in the images on the right.
    • Presumptive identification of the four genera of slower-growing pathogenic dematiaceous molds can be made by observing specific types of conidiation. Match the names of the species of dematiaceous pathogenic fungi with the corresponding microscopic features illustrated in the images on the right.
    • Match the name of each dematiaceous fungus listed in the drop-down box with its most likely disease.
    • Match the name of each fungal species listed with its most likely corresponding morphologic features.
    • Match the name of each fungal species listed in the drop-down box with its most likely corresponding morphologic feature.
    • Match the names of each of the fungi listed with its appropriate category.
    • Match the names of each of the fungi listed with its appropriate category depending upon whether the multi-celled macroconidia are divided by both longitudinal and transverse septa (dictyospores) or divided by only transverse septa.
    • Match the names of each of the fungi listed with its appropriate category indicating the degree of pathogenicity.
    • What is the fungal species most likely associated with the granulomatous infection seen in this image, illustrating segmented, dark brown-staining grains with a giant cell?
    • The infrequently encountered mold that is represented in this image begins as a gray-white colony that blackens with maturity as the hyphae become darkened and single, globose, black conidia are produced. What is the most likely identification of this fungus?
    • The multi-celled conidia of this dematiaceous mold are divided into cells by what are called distosepta (pseudosepta), indicating that the individual cells are surrounded by a sac-like wall that is distinct from the outer cell wall of the conidium. What is the most likely identification of this mold?
    • Which fungus is characterized by oval or curved, dark-staining, multicellular macroconidia divided only by transverse septa?
    • What is the type of sporulation of the dematiaceous mold that is shown in this image called?
    • Which of the following dematiaceous fungi is most likely represented by this black, suede-like colony that grows no larger than a dime after 7 days of incubation?
    • Which dematiaceous fungus can be ruled out based on the illustrated colony’s growth to a diameter of 3–4 cm within 5 days?
    • Which dematiaceous fungus may produce both acrotheca and rhinocladiella types of sporulation?
    • The black yeast colony shown in this photograph may represent any of the following dematiaceous molds, except which one?
    • Which fungus is most characteristically associated with the chain of annelloconidia shown in this photomicrograph, distinguished by their deeply staining, truncated bases?
    • Which fungus is most characteristically associated with the long, flask-shaped, tapered phialide shown in this image (arrow), featuring a flat, saucer-like terminus among the dematiaceous hyphae?
    • With which disease is the dematiaceous fungus shown in this image most likely associated?
    • The dematiaceous conidium shown in this image was obtained from a tiny portion of a dark colony that grew to maturity in six days. Spores incubated in a saline mount for four hours developed germ tubes from both terminal cells. Which mold is confirmed by the observed features?
    • What chief microscopic feature differentiates Ulocladium species from the closely resembling Stemphylium species?
  • References
    • References

Additional Information

Level of Instruction: Intermediate to advanced
Intended Audience: Microbiologists, medical laboratory scientists, medical laboratory technicians, and medical laboratory students.
Author Information: 
Elmer W. Koneman, MD, received his graduate degree from the University of Colorado School of Medicine in Denver, Colorado, and until his passing in 2020, was a Professor Emeritus at their Department of Pathology. He was the author of numerous journal articles and books, including Color Atlas and Textbook of Diagnostic Microbiology, 7th Edition, 2017. 
Margaret Reinhart, MS, MLS(ASCP), is the MLS Program Director and Senior lecturer in Biological Sciences at the University of the Sciences in Philadelphia, PA, where she teaches hematology, clinical immunology, parasitology, and other related courses. She is also an adjunct instructor in Hematology at Pennsylvania Hospital, Philadelphia, PA. She holds a Masters Degree in Biology and in Health Care Administration.
The authors have no conflict of interest to disclose. 
Reviewer Information: Judi Bennett, BSM, MLS, is an Education Developer with MediaLab by Vastian, bringing over 30 years of experience as a medical laboratory scientist. Before joining MediaLab in 2010, she held key leadership roles, including Clinical Laboratory Manager, Microbiology Supervisor, and Senior Systems Analyst at Gwinnett Health System in Lawrenceville, Georgia. Her extensive knowledge of laboratory operations, combined with a strong commitment to healthcare quality and education, fuels her passion for developing engaging and effective learning tools for the next generation of laboratorians.
Course Description: This course describes and identifies hyaline and dematiaceous fungi. Many photomicrographs are used to assist in the recognition of organisms in culture and microscopically.