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Microbiology Exam 1 > Intro to Clinical Mycology > Flashcards

Intro to Clinical Mycology Flashcards

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1
Q

Saprophytes

A

Plant, fungus, or microorganism that lives on dead or decaying matter

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2
Q

Commensal vs Symbiotic vs Parasitic

A

C: no benefit or harm to us
S: mutually beneficial
P: cause disease in us

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3
Q

Examples of Mycotoxins

A

Ergot Alkaloids (Salem Witch Trials; women having psychotic episodes due to consumption of ergot alkaloids via bread)
Aflatoxin (Peanuts)
Stachybotrys (Black mold in houses)
Recreation “shrooms”

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4
Q

What are the two important differences/targets that fungal cells possess compared to humans?

A

Cell wall and Membrane sterol composition (have ERGOSTEROL rather than cholesterol)

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5
Q

What type of pathogenic yeast possess a capsule?

A

Cryptococcus neoformans

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6
Q

Most of our immunologic response is due to ____

A

Cell wall

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7
Q

Fungal Cell Wall Function

A

-Shape, rigidity, strength, protection from osmotic shock

***~90% of cell mass is cell wall

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8
Q

Fungal Cell Wall Composition: Polymer vs Monomer

A

Polymer: Chitin, Chitosan, Cellulose, a-Glucan, B-Glucan, Mannan

Monomer: N-acetyl glucosamine, D-Glucosamine, D-Glucose, D-Glucose, D-Mannose

*** = bolded on slide

Cell wall also contains proteins (mannoproteins)

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9
Q

Fungal Cell Membrane (Function, Structure)

A

F: Regulate nutrient flow, contains cytoplasm

S: Typical phospholipid bilayer, Unique sterol composition (Humans = cholesterol, Fungi = ERGOSTEROL)

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10
Q

Fungal Structures and Classification

A

Yeast (e.g. Candida)
Molds
Both (called DIMORPHIC when they can grow as both; e.g. molds in bat droppings transform into yeast in the body of humans)

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11
Q

Yeast (Morphology and Reproduction)

A

M: Unicellular; spherical or ellipsoid
R: Budding

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12
Q

What type of yeast produces a germ tube?

A

Candida albicans

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13
Q

Blastoconidia

A

Bud

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14
Q

Pseudohyphae

A

Chains of elongated buds; look like hyphage in bacteria

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15
Q

Germ Tube

A

Looks like SPOON; yeast send out a SINGLE long narrow extension (“bud gone wrong”)

99% of the time will be Candida albicans

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16
Q

Mold Characteristics (2 of them)

A
  • Hyphae (i.e. Mycelium): can be vegetative (grow into substrate) or aerial (grow into air)
  • Septa (Septum): septa or aspetate (coenocytic)
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17
Q

Mold Reproduction

A

Both Asexual (via Conidia) and Sexual (via Spores)

***Conidia and Spores will be used interchangeably

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18
Q

Mold: Asexual Reproduction

A

Via Conidia
-Can be either Micro-, Macro-, or Chlamydo- (Arthro-)

Chlamydo/Arthro = conidia right within the strand of a hyphae

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19
Q

Fungal infections are diagnosed ____

A

Visually; there are not a lot of biochemical tests that can be done for them

20
Q

Superficial Mycoses

A

Infections of the outermost layers of skin and hair
e.g. Pityriasis versicolor, Tinea nigra, Black and White Piedra

“These are more COLONIZATIONS than infections”

21
Q

Cutaneous Mycoses

A

Infection which extends deep into the epidermis as well as invasive hair and nail infections
e.g. Dermatophyte infections- Ringworm, Athlete’s Foot, Jock Itch

***Most common fungal infections

22
Q

Subcutaneous Mycoses

A

Infections involving the dermis, subcutaneous tissues, muscle, and fascia
e.g. Sporotrichosis, Chromoblastomycosis

23
Q

Systemic Mycoses

A

Infections that originate in the LUNG but may be spread to any organ in the body
e.g. DIMORPHIC fungi: Histoplasmosis, Blastomycosis, Paracoccidioidomycosis, Coccidioidomycosis. Yeast: Cryptococcosis

***All acquired initially by INHALATION

24
Q

Opportunistic Mycoses

A

Infection associated primarily with immunosuppressed individuals
e.g. Candidiasis, Aspergillosis, Zygomycosis, Pneumocystis carinii pneumonia

25
Q

____ Immune System is generally sufficient to prevent fungal infections in healthy individuals

A

Innate

26
Q

Who are at risk for fungal infections?

A

Burn patients, immunocompromised patients, patients who are constantly exposed to fungal spores

27
Q

How else can fungi gain access to host tissues?

A

Traumatic implantation (e.g. rose bush thorns, sporotrachosis, cuts on the feet) or inhalation

28
Q

The severity of disease caused by fungi depends upon the size of the _____, magnitude of _______, the ability of fungi to ________, and the ______ of the host.

A

Inoculum, Tissue Destruction, Multiply in tissues, Immunologic status

29
Q

What is most effective at controlling and eliminating fungal infection: Humoral (antibody) or Cell-Mediated Immunity?

A

Cell-Mediated (becomes compromised with Immunosuppression - steroids or radiation, AIDS, T-cell and neutrophil deficits)

30
Q

Main concern with antifungal drugs

A

Crossover in toxicity to the host due to lack of unique features

31
Q

Topical Therapy

A

Used for superficial/cutaneous infections

32
Q

Systemic Therapy

A

Used for subcutaneous and systemic infections, some cutaneous

33
Q

What are the most common targets of Antifungals?

A

Cell wall and Cell membrane

34
Q

What two parts of cell wall synthesis are inhibited?

A

Glucan synthesis (by Echinocandins)

Chitin synthesis (by Nikkomycin)

35
Q

What part of cell membrane synthesis are inhibited?

A

Ergosterol synthesis (by Azoles and Allylamines)

36
Q

How do Polyenes act as Antifungals?

A

Bind to Ergosterol and disrupt fungal cell membrane

37
Q

What drugs inhibit Ergosterol synthesis?

A

Azoles, Allylamines, Thiocarbamates, Morpholines

Mnemonic: “A lil ATM” –> Allyl ATM

38
Q

What drug binds directly to Ergosterol?

A

Polyenes

39
Q

Amphotericin B (Agent and Mechanism)

A

A: Polyene***

M: Binds to ergosterol in the membrane, causing a PORE to form, leading to osmotic disruption/leakage/influx of fluid into cell

*** = Definitely know this

40
Q

Echinocandins (e.g. caspofungin, anidulafungin, micafungin)

A
  • Cell wall synthesis inhibitor*
  • Inhibits B-glucan synthesis (via 1,3-B-D-glucan synthase) and is only effective against fungi that use a lot of B-glucan in their cell wall synthesis
    e. g. Candida and Aspergillus
41
Q

Laboratory Diagnosis of Fungal Infections

A

Diagnosis of fungal infections is frequently made by DIRECT VISUALIZATION OF FUNGAL ELEMENTS in infected tissues

42
Q

KOH Preparation

A

Used to examine hair, nails, skin scrapings, fluids, exudates, or biopsies

Dissolves away nails, skin, hair, etc at a greater rate than fungal structures to allow visualization of fungal structures (i.e. hyphae, large yeast, spherules, and sporangia)

43
Q

All dyes tend to bind _____

A

Carbohydrate-rich cell wall (e.g. Chlorazol Black, Calcofluor White)

Tissue sections/Histological specimens may also use specialized stains to enhance detection of fungi (e.g. Gomori methlamine silver (GMS) and Periodic acid-Schiff (PAS))

44
Q

All fungi stain ____

A

Gram Positive

45
Q

When you see an India Ink Stain, think

A

Cryptococcus neoformans

46
Q

Germ Tube Test

A

Used to identify Candida albicans

-Serum is mixed with sample for a couple of hours, and if germ tubes form, then you know it is Candida albicans

47
Q

Examples of Fungal Lab Cultures

A

Sabouaud’s dextrose agar
Cornmeal agar
Czapek Dox agar

Microbiology Exam 1 (11 decks)

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