EXAM 1 Mycology

Question 1

describe the kingdom fungi

Answer 1

• myceteae
• mycology - yeasts and molds
• eukaryotes
• ubiquitous in nature
  
  • decomposers/saprophytes
  • part of our normal flora (candida spp.)
• >200,000 species, <200 human pathogens

Question 2

describe the fungal cell wall structure

Answer 2

Question 3

describe the phenotypic morphology of yeasts

Answer 3

• single cells
• colonies in culture
  
  • single
  • creamy, mucoid
  • facultative anaerobes

Question 4

describe the phenotypic morphology of molds

Answer 4

• multicellular, filamentous
  
  • thread-like filaments = hyphae
  • hyphae interweave = mycelium
• colonies in culture
  
  • fuzzy, velvety
  • obligate aerobes

Question 5

are true hyphae usually mold or yeast? what about pseudohyphae?

Answer 5

true hyphae = mold

pseudohyphae = yeast

Question 6

what is sporulation?

Answer 6

• reproduction; can be either sexual or asexual
• asexual state = anamorph
• sexual state = teleomorph

Question 7

describe the anamorph state

Answer 7

• asexual state
• mitotic division of haploid nucleus most common
  
  • yeast reproduce by budding
  • molds reproduce by producing conidia or by separation of hyphal elements

Question 8

describe the teleomorph state

Answer 8

• sexual state
• diploid nucleus divides by meiosis
  
  • haploid nuclei of donor and recipient fertile cells fuse
  • mold can also reproduce by producing sexual spores

Question 9

what are dimorphic fungi?

Answer 9

important group of geographically restricted (regionally endemic) pathogens that exist as a mold when cultured at 25-30*C and yeast at 35-37*C

Question 10

what are opportunistic fungi?

Answer 10

only cause disease in compromised host

Question 11

what are the 5 main risk factors for disease in humans?

Answer 11

• immunocompromised
• premature infants
• critically ill and hospitalized patients
• travelers and residents of endemic areas
• direct contact with animals or infected materials

Question 12

name 6 examples of immunocompromised risk factors

Answer 12

• solid organ and stem cell transplant recipients
• advanced HIV/AIDS
• malignancy
• other immunodeficiency
• autoimmune disease
• metabolic disease

Question 13

name 3 natural protection against disease

Answer 13

• natural barriers
• innate immunity
• cell mediated immunity

Question 14

what are the advantages and disadvantages of direct microscopy?

Answer 14

• advantages
  
  • fast and cheap
• disadvantage
  
  • insensitive

Question 15

what are the advantages and disadvantages of culture?

Answer 15

• advantages
  
  • gold standard from sterile body site
  • allows genus/species level ID and susceptibility testing
• disadvantages
  
  • delayed results
  • difficult to obtain from certain sites
  • lack of sensitivity
  • lack of specificity from non-sterile sites

Question 16

what are the advantages and disadvantages of histopathology?

Answer 16

• advantages
  
  • gold standard for invasive disease
• disadvantages
  
  • difficult to obtain
  • not species specific

Question 17

what are the 3 classic diagnostic approaches?

Answer 17

• direct microscopy
  
  • 10% KOH + calciflour white
• culture
• histopathology

Question 18

name the 2 novel diagnostic approaches

Answer 18

• serum biomarkers
  
  • cell wall components
    
    • galactomannan
    • 1,3-beta-D-glucan
• direct detection
  
  • nucleic acid amplification tests
    
    • PCR/sequencing
    • in situ hybridization

Question 19

describe the 2 current methods for identification

Answer 19

starting with a pure culture…

• proteomic identification
  
  • matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS)
• targeted gene sequencing
  
  • conserved regions and variable regions in all fungi

Question 20

will yeast stain gram positive or negative?

Answer 20

yeast stains gram positive (purple stain)

Question 21

what are the 5 main candida species?

Answer 21

• c. albicans
• c. glabrata
• c. krusei
• c. parapsilosis
• c. tropicalis

Question 22

candida spp. are part of our normal flora. where are they found?

Answer 22

skins, mouth, upper respiratory tract, bowel, vagina

Question 23

what are common infections caused by candida spp.?

Answer 23

thrush, vaginitis, balanitis, diaper rash, esophagitis, intra-abdominal abscesses, blood stream infection

Question 24

describe rhinocerebral zygomycosis

Answer 24

• aka mucormycosis (diseases caused by fungi of the order mucroales)
• rare infection. most common species
  
  • mucor, rhizopus, rhyzomucor
  • thrive in high glucose, acidic environment (ketone reductase)
• airborne spores inhaled
  
  • anagioinvasive
• medical and surgical emergency

Question 25

name the risk factors for rhinocerebral zygomycosis

Answer 25

• hematologic malignancy/HSCT (esp. voriconazole)
• steroids
• iron overload
• diabetes with ketoacidosis
• AIDS
• IV drug use
• trauma/burns

Question 26

name the drug classes to treat candidiasis

Answer 26

• azoles (fluconazole)
• echinocandins (caspodungin)
• polyenes (amphotericin)

Question 27

what are the two most common species of candida?

Answer 27

• c. albicans and c. glabrata
• c. glabrata often resistant to fluconazole

Question 28

name the 6 dimorphic/endemic pathogenic fungi

Answer 28

• blastomyces dermatidis
• coccidiodes immitis/posadasii
• histoplasma capsulatum/duboisii
• paracoccidioides brasiliensis
• penicillium marneffei
• sporothrix schenckii

Question 29

name the 6 opportunistic pathogenic fungi

Answer 29

• aspergillus spp.
• candida spp. (yeast)
• cryptococcus neoformans/gattii (yeast)
• mucor spp. (zygomycete)
• rhizopus spp. (zygomycete)
• pneumocystis jirovecii

Question 30

name the 4 cutaneous pathogenic fungi

Answer 30

• malassezia furfur (yeast)
• epidermophyton spp.
• microsporum spp.
• trichophyton spp.