Intro to Clinical Mycology Flashcards
Define Mycology
The study of fungi (yeasts and molds)
T/F Fungi are eukaryotic
True
How do fungi obtain nutrients?
Absorption
What does “Mycoses” mean?
Fungal infections
What is another name for Kingdom Fungi?
Myeteae
T/F Fungi are Chemotrophs
True
What is a chemotroph?
Oragnism that requires organic compounds for both carbon and energy sources
What is the most common fungi we will come across in dentistry?
Candida spp.
Define Saprophyte
Organisms that live off decaying matter
Name the 3 targets of anti-fungal therapy
- Ergosterol
- (1-3) Beta-D glucan synthase
- 14 Alpha-demethylase
Name the main classes of drugs used in anti-fungal therapy, what their targets are, how they work, and lisit examples of each
- POLYENES
- Target: Ergosterol
- Example: Amphotericin products
- Binds to ergosterol and disrupt osmolaric integrity of cell membrane
- AZOLES
- 14 a Demethylase
- Examples: itraconazole, voriconzole, posaconazole
- inhibits its target resulting in a loss of normal fungal sterols and accumulation of 14a-demethyl sterols within the fungus
- ECHINOCANDINS
- (1-3) B-D-glucan synthase
- Examples: capsofungin, micafungin, anidulafungin
- They inhibit their target and block cell wall synthesis
What is Flucytosine and how is relevant to fungi?
- It is a drug used to treat fungal infections especially from members of teh candida and cryptococcus
- It is selectively converted by fungi to active metabolites and inhibits fungal RNA and DNA synthesis
What are the components of the fungal cell wall?
- Mannan
- Beta-glucans
- Chitin
Describe the phenotypic morphology of yeasts vs. molds
YEASTS:
- Single cells
- Colonies in Culture
- Single
- Creamy, mucoid
- Facultative anaerobes
MOLDS:
- Multicellular, filamentous
- Hyphae: thread like filaments
- Mycelium: Hyphae interweave
- Colonies in culture:
- Fuzzy, Velvety
- Obligate aerobes
What is microscopic vs. macroscopic morphology?
Microscopic: Arrangement of reproductive bodies in culture, tissue histopathology
Macroscopic: culture
Define Blastoconidia
Yeast buds
Define Pseudohyphae
A chain a blastoconidia
Which produces true hyphae, yeast or mold?
Mold
T/F C. Albicans may also produce true hyphae
True
What do pseudohyphae and hyphae help yeast do?
Invade deeper tissues after it colonizes the epithelium
Name two types of hyphae and give an example of both
- Septate Hypha
- Aspergillus Sp.
- Nonseptate Hypha
- Zygomycete sp.
What is a germ tube?
Long branching filaments lacking complete septa form
Describe septa
Internal cross-walls that divide hyphae into cells and are usually perforated by pores large enough for ribosomes, mitochondria, and sometimes nuclei
What is typically the major structural polymer of a cell wall and how does this differ from plants?
Chitin
*Plants usually have cellulosic cell walls
What are the two modes of reproduction for molds?
Asexual and sexual sporulation
Describe asexual sporulation
- Mitotic division of haploid nucleus most common
- Molds reproduce by producing conidia or by separation of hyphal elements
Describe sexual sproulation
- Diploid nucleus divides by meiosis
- Haplpoid nuclei of donor and recipient fertile cells fuse
- Mold can also reproduce by producing sexual spores
What are molds called that reproduce in an asexual or sexual state?
Asexual: Anamorph
Sexual: Teleomorph
What are conidia?
a spore produced asexually by various fungi at the tip of a specialized hypha.
What is the vegetative mycelium?
The portion of the mycelium that anchors the mold and absorbs nutrients.
- composed of begetative hyphae
What is the aerial mycelium?
Portion of the mycelium that produces asexual reproductive spores
*composed of aerial hyphae
Give examples of asexual and sexual fungi
Asexual:
-Scedosporium apiospermum
Sexual:
- Pseudallescheria boydii
- Aspergillus Nidulans
- Apergillus glaucus
- Saccharomyces spp.
List the dimorphic/endemic, opportunistic, and cutaneous fungi and indicate if any are yeasts or zygomycetes (also review examples of mycoses from these fungi)
Write out the table from slide 10
Name risk factors associated with mycoses
- Immunocompromised
- solid organ and stem cell transplant recipients
- Advanced HIV/AIDS
- Malignancy
- Other immunodeficiency
- Autoimmune diseae
- Metabolic disease
- Premature infants
- Critically ill or hospitalized patients
- Travelers and residents of endemic areas
- Direct contact with animals or infected materials
List the 3 methods for direct specimen diagnostic testing, advantages and disadvantages of each
- DIRECT MICROSCOPY
- Advantages: Fast, cheap
- Disadvantages: Insensitive
- CULTURE
- Advantages:
- Gold standard from sterile body site
- Allows genus/species ID and susceptibility testing
- Disadvantages:
- Delayed results
- Difficult to obtain from certain sites
- Lack of sensitivity
- Lack of specificity from non-sterile sites (colonization vs. infection)
- Advantages:
- HISTOPATHOLOGY
- Advantages:
- Gold standard for invasive disease
- Disadvantages
- Difficult to obtain
- Not species specific
- Advantages:
What are the two categories for diagnostic approaches? Describe them both
- CLASSIC
- Direct Microscopy
- 10% KOH + Calcifluor white
- Culture
- Histopathology
- Direct Microscopy
- NOVEL
- Serum Biomarkers
- Cell wall components: Galactomann, 1, 3-B-D-Glucan
- Direct detection
- PCR/sequencing
- In situ hybridization
- Serum Biomarkers
What does Calcifluor white bind?
Selectively binds to cellulose and chitin
What are the current methods for identification starting with a pure culture? Describe what they both entail.
- PROTEOMIC IDENTIFICATION
- Matrix Assisted Laser Desorption Ionization (MALDI)
- Time of flight (TOF)
- Mass Spectrometry (MS)
- TARGETED GENE SEQUENCING
- Conserved and variable regions in all fungi
What are some buzz words for Candida spp?
- Gram positive organisms
- Budding yeast with pseudohyphae
- Growth on routine bacterial culture media (blood agar plate and chocolate agar plate) within 24-48 hours
What are some buzz words for Candida Albicans?
- Creamy colonies on bacterial agar often have little “feet”
- Forms germ tubes when incubated in serum for 3 hours
- Forms large thick walled terminal chlamydospores on specialized agar
What are the 5 most common candida species? Which among them are the 2 most common and which are resistant to fluconazole?
- C. Albicans
- C. Glabrata
- C. Krusei
- C. Parapsilosis
- C. Tropicalis
Two most common:
- C. Albicans
- C. Glabrata
Resistante to Fluconazole:
C. Glabrata
Where do we find candida as part of our normal flora?
Skin, mouth, upper respiratory tract, bowel, vagina
What are some common infections caused by candida?
- Thrush
- Vaginitis
- Balanitis
- Diaper rash
- Esophagitis
- intra-abdominal abscesses, blood stream infection (candidemia)
Name the drug classes to treat candidiasis
- Azoles (fluconazole)
- Echinocandins (capsofungin)
- Polyenes (amphotericin)
What is Rhinocerebral Zygomyocosis?
What are the most common species that cause it?
What are some risk factors for it?
Is it a medical/surgical emergency?
- Also referred to as Mucormycosis (diseases caused by fungi of teh order mucorales), it is a rare infecdtion
- Most common species that cause it are Mucor, Rhizopus, and Rhizomucor. They thrive in high glucose, acidic environments (ketone reductase)
- Risk factors include:
- Hematologic Malignancy
- Steroids
- Iron overload
- Diabetes with ketoacidosis
- AIDS
- IV drug abuse
- Trauma/Burns
- Yes it is a medical and surgical emergency
What does angioinvasive mean?
marked by or causing infiltration of blood vessels
*Airborne spores of Rhinocerebral Zygomycosis are this if inhaled
