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Microbiology > Mycology Exam 3 (Yeast + Opportunistic) > Flashcards

Mycology Exam 3 (Yeast + Opportunistic) Flashcards

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Biology 101 flashcards
1
Q

Describe yeasts

A

Eukaryotic, unicellular organisms

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2
Q

What morphological features are helpful in differentiating yeasts?

A
  • Size of the cells
  • Presence or absence of capsule
  • Production of chlamydospores
  • Broad-based or narrow-necked budding
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3
Q

Reproduction of yeast

A

Asexually by blastoconidia (budding)

Sexually by ascospores or basidiospores

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4
Q

Describe the budding process of yeast

A

Outpouching of yeast cell wall forms bud/daughter cell, cell wall septum created, daughter cell detaches from mother cell and a bud scar is left

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5
Q

Germ tube

A

Tubular outpouching of cell wall - Does NOT have a constriction at its base, initial stage of true hyphae formation

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6
Q

Pseudohyphae

A

Cell wall constrictions but no true intracellular septation

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7
Q

Most yeast infections caused by ______ species (also the most commonly IDed in the lab)

A

Candida

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8
Q

C. albicans complex includes:

A

C. candida
C. dubliniensis
C. africana

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9
Q

Thrush

A

Infection of the mucous membranes in the mouth

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10
Q

Toxin production of Candida sp

A

Candidalysin –> initiates epithelial invasion

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11
Q

Name standout feature noted about C. auris

A

Resistant to MANY antifungals, including fluconazole

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12
Q

Name standout feature noted about C. glabrata

A

Can cause endocarditis, meningitis, and disseminated disease
Trehalose positive

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13
Q

Name standout feature noted about C. tropicalis

A

Prevalent in patients with hematologic malignancies

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14
Q

Name standout feature noted about C. krusei

A

Intrinsically resistant to azoles

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15
Q

Name standout feature noted about C. parapsilosis complex

A

Primary cause of fungemia in the NICU, second most commonly isolated Candida spp. in blood cultures

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16
Q

True septate hyphae may be produced by Candida _______

A

albicans complex

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17
Q

Yeast cells are gram ____

A

positive

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18
Q

How do you ID C. albicans?

A

Colonies possess feet on agar, starlike
Production of germ tubes or chlamydoconidia

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19
Q

How to ID C. glabrata?

A

Ferments glucose and trehalose

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20
Q

How to ID C. tropicalis?

A

Ferments Sucrose and maltose

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21
Q

Germ Tube Test (purpose, testing time)

A

ID of C. albicans
Results available within 3 hours

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22
Q

Rapid Trehalose Test (purpose, positive color and negative color)

A

presumptive ID of C. glabrata
Positive color = yellow
Negative = blue/green

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23
Q

What is the major Cryptococcus sp and what is it associated with in nature?

A

C. neoformans
Associated with pigeon or other bird excreta

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24
Q

What is one of the most commonly isolated species in immunocompromised hosts worldwide?

A

C. neoformans

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25
Q

Pathogensis and Disease of Cryptococcus (population)

A

Found in immunocompromised patients, ESPECIALLY those with decreased CD4 T-cells, organism can travel to CNS and cause meningitis

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26
Q

What is a standout feature of Cryptococcus, microscopically?

A

Polysaccharide capsule that protects the yeast from dessication

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27
Q

Lab ID of Cryptococcus

A

Polysaccharide capsule that is highly refractile (can be observed with India Ink) and extreme variation in the size of the yeast cells

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28
Q

India Ink Stain (purpose, specimens used)

A

Rapid assessment tool for the ID of Cryptococcus sp.
Specimens = CSF, urine, and other body fluids

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29
Q

Final ID of Cryptococcus (based on culture/growth)

A

Brown to black color on niger seed/birdseed agar due to Phenoloxidase oxidizing to melanin (ONLY produced by C. neoformans)

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30
Q

Standout Info : Geotrichum spp.

A

Major organism = G. candidum
Normal human microbiota
Rectangular arthroconidia on cornmeal agar

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31
Q

How is Geotrichum differentiated from Trichosporon spp?

A

Urease testing
Trichosporon = positive urease
Geotrichum = negative urease

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32
Q

Standout features of Rhodotorula spp.

A
  • Found in fruit juice, milk, or salt and freshwater
  • Normal skin flora
  • R. mucilaginosa is relevant species
  • Coral pink to salmon-colored colonies
  • Associated with fungal peritonitis in patients on CAPD
  • Urease positive
  • Produce capsules
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33
Q

Standout features of Saccharomyces spp.

A

S. cerevisiae = major organism
AKA baker’s yeast
Common yeast found in baking and probiotics
Rarely associated with disease

34
Q

Why is there an increased incidence of Saccharomyces cerevisiae infections?

A

Use of probiotics for treatment of antibiotic-associated diarrhea

Contact with health foods containing the organism

35
Q

Most opportunistic fungal pathogens that are encountered in the lab are considered what term? Should they be considered/reported?

A

Saprobes - saprophytic/environmental organisms
YES - should still be ID/reported because they are potential pathogens

36
Q

In what environment are many opportunistic fungal pathogens acquired?

A

Construction, demolition, or remodeling of buildings through inhalation or they are hospital acquired

37
Q

Which organisms are in the Mucorales family? (6)

A
  • Rhizopus sp.
  • Mucor sp.
  • Lichtheimia sp.
  • Rhizomucor sp.
  • Cunninghamella sp.
  • Syncephalastrum sp.
38
Q

Which organism are the opportunistic Hyaline Molds? (6)

A
  • Penicillium sp.
  • Aspergillius sp.
  • Fusarium sp.
  • Scopulariopsis sp.
  • Paecilomyces sp.
  • Chrysosporium sp.
39
Q

Which opportunistic fungal pathogen is considered “other” and is not a part of the hyaline or mucorales family?

A

Pneumocystis jirovecii

40
Q

The Mucorales family were formerly known as…..?

A

Zygomycetes

41
Q

Characteristics for ID of Mucorales Family

A
  • Produce large, ribbonlike hyphae, irregular in diameter, contain occasional septa
  • Have sporangia and sporangiospores
42
Q

What are sporangia? Sporangiospores?

A

Sporangia - large, saclike fruiting structures that release sporangiospores (spherical, yellow/brown)

**Be able to label these on a diagram probably

43
Q

What is a sporangiophore?

A

A supporting structure for the sporangium

**Be able to label these on a diagram probably

44
Q

What is a stolon?

A

Occasional septate hyphae that connect sporangiophores

**Be able to label these on a diagram probably

45
Q

What is a Rhizoid?

A

Root-like structures that spread from stolons
Presence or absence is helpful in ID to different Mucorales family

**Be able to label these on a diagram probably

46
Q

Mucorales family typically only causes disease in immunocompromised patients. What SPECIFIC patients do these fungi typically have a higher chance of infecting?

A

Diabetes Mellitus patients due to decreased pH and sugary blood

47
Q

How are Mucorales family fungi acquired?

A

Through inhalation of spores or percutaneously

48
Q

What disease does Mucorales family cause?

A

Mucormycosis, marked with rapid vascular invasion so they rapidly produce thrombosis and necrotizing tissue

49
Q

What is the rhinocerebral form of Mucormycosis?

A

Vascular invasion of specifically the nasal mucosa, palate, sinuses, orbit, face, and brain

50
Q

Special specimen transport of Mucorales

A

Must be transported within 2 hrs to the lab, b/c Mucorales are extremely sensitive to environmental changes

51
Q

Special characteristics to ID Mucorales microscopically

A

Under calcofluor/KOH prep, Mucorales have branching, broad-diameter, predominantly nonseptate hyphae

52
Q

Special characteristics of Mucorales colony growth

A

Fluffy, white to gray to brown hyphal growth resembling cotton candy

Considered lid lifters because hyphae can grow very fast and lift agar plate lid

53
Q

What is apophysis?

A

Swelling of the sporangiophore below the columellae

54
Q

What is columella?

A

The central axis of the sporangia

55
Q

Slide 14 has an image of labeling structures of Mucorales fungi, probably should know it

A

If only I could insert a photo without PAYING

56
Q

Mucor morphology is slightly different than other species in the Mucorales family…. how?!

A

NO rhizoids or stolons present in microscopic morphology!

57
Q

What is standout about Lichtheimia microscopic morphology?

A

Pyriform sporangia with a funnel-shaped apophysis

58
Q

What is among the most COMMONLY encountered fungi in the clinical laboratory??

A

Aspergillus species

59
Q

Describe the disease that Aspergillus species causes

A

Aspergillosis
Pulmonary or sinus fungus balls (aspergilloma)
External otomycosis (fungus ball of external auditory canal)
Onychomycosis (infection of nail/ned bed)

Most commonly a primary pulmonary infection that disseminates

60
Q

What is standout about Aspergillus fumigatus characteristic?

A

THERMOTOLERANT –> can withstand temperatures up to 45C

61
Q

What is standout about Aspergillus fumigatus microscopic morphology?

A

Conidiophores have a T/L shaped “foot cell” at their base
Tip of conidiophores have bottle-shaped phialides that cover upper half of its surface only

62
Q

What is standout about Aspergillus flavus colony morphology??

A

It is yellow/green! (Hence, flavi = yellow)

63
Q

What is standout about Aspergillus flavus microscopic morphology?

A

Globose vesicles
Phialides can either be UNISERATE –> produced directly from the vesicle surface

OR BISERATE –> produced from a primary row of cells called metulae

64
Q

What is standout about Aspergillus niger colony morphology?

A

Begins as a yellow colony, soon develops black dotted colony, and eventually turns jet black and powdery

65
Q

What is standout about Aspergillus niger microscopic morphology?

A

Biserate phialides
ENTIRE surface of vesicle is covered

These look like dandelions :)

66
Q

What are the 2 most commonly isolated Fusarium species?

A
  1. most common - Fusarium solani complex
  2. Fusarium oxysporum complex
67
Q

What is the disease of Fusarium sp. like?

A

Causes mycotic keratitis after traumatic implantation
Disseminated fusariosis commonly accompanied by fungemia

68
Q

Describe the microscopic morphology of Fusarium sp

A

Microconidia –> borne in gelatinous heads (whatever TF that means)
Macroconidia –> large, sickle/boat shaped contain numerous septations

69
Q

Most Penicillium species are considered ____________, but ___________ is the only species considered a true fungal pathogen rather than an opportunistic organism.

A

Contaminants; Talaromyces marneffei (formerly Penicillium marneffei)

70
Q

Describe the microscopic morphology of Penicillium species

A

“Brushlike conidiophores”
Conidiophores produce metulae, phialides arise from metulae, chains of conidia

(looks like fingers or a mop)

71
Q

Describe the microscopic morphology of Scopulariopsis sp.

A

Annellophores produce produce flask shaped annelides which support lemon-shaped conidia in chains

Conidia are large, have a flat base, and are rough-walled

72
Q

What is the microscopic morphology of Paecilomyces like?

A

Long, delicate, tapering phialides
Chains of small, oval conidia are easily dislodged

73
Q

What is the causitive agent of Pneumocystis?

A

Pneumocystis jirovecii

74
Q

What is PCP?

A

Pneumocystis pneumonia; associated with P. jirovecii

75
Q

P. jirovecii was originally thought to be a ________, not a fungi. Why?

A

Trypanosome.
Due to similar morphology to a protozoa and this organism responds to antiprotozoal drugs, NOT antifungals

76
Q

What are the 3 life cycle stages of P. jirovecii? What is the diagnostic form?

A
  1. Trophic form (trophozoite)
  2. Sporozoite (precyst)
  3. Ascus (cyst) –> diagnostic form
77
Q

How does P. jirovecii differ from other fungi?

A
  1. Cell membrane contains cholesterol, not ergosterol
  2. Only 1-2 copies of small ribosomal subunit gene
78
Q

Describe the epidemiology of P. jirovecii (disease manifestation, notable fact, transmission)

A

Most commonly presents as pneumonia
The most common opportunistic infection among those with HIV/AIDS in the U.S.

Transmits person to person via airborne particles

79
Q

What is the disease process of P. jirovecii?

A

Inhalation
Trophic form adheres to pneumocytes (cells of lungs)
Replicate intracellularly, filling alveolar space with eosinophilic foamy material
Infection leads to hypoxemia, cough, fever, etc.

80
Q

What type of specimen is the best for detection of P. jirovecii?

A

BAL, sputum
Biopsy of infected organ if extrapulmonary cysts

81
Q

What is the diagnostic form of P. jirovecii, vs what is the predominant morphology? Explain.

A

Cyst form is the diagnostic stage because they are more easily distinguishable (contain intracystic bodies)

Predominant morphology is the trophic form, but very hard to visualize.

82
Q

What is another way, other than microscopic morphology, that P. jirovecii can be diagnosed?

A

Direct detection of (1,3)-beta-D-glucan
Secretes it in larger amounts than other fungi

Microbiology (24 decks)

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