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Flashcards in Intro to Clinical Mycology Deck (47):
1

Saprophytes

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

2

Commensal vs Symbiotic vs Parasitic

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

3

Examples of Mycotoxins

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"

4

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

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

5

What type of pathogenic yeast possess a capsule?

Cryptococcus neoformans

6

Most of our immunologic response is due to ____

Cell wall

7

Fungal Cell Wall Function

-Shape, rigidity, strength, protection from osmotic shock

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

8

Fungal Cell Wall Composition: Polymer vs Monomer

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)

9

Fungal Cell Membrane (Function, Structure)

F: Regulate nutrient flow, contains cytoplasm

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

10

Fungal Structures and Classification

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)

11

Yeast (Morphology and Reproduction)

M: Unicellular; spherical or ellipsoid
R: Budding

12

What type of yeast produces a germ tube?

Candida albicans

13

Blastoconidia

Bud

14

Pseudohyphae

Chains of elongated buds; look like hyphage in bacteria

15

Germ Tube

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

99% of the time will be Candida albicans

16

Mold Characteristics (2 of them)

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

17

Mold Reproduction

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

***Conidia and Spores will be used interchangeably

18

Mold: Asexual Reproduction

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

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

19

Fungal infections are diagnosed ____

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

20

Superficial Mycoses

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

Cutaneous Mycoses

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

Subcutaneous Mycoses

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

23

Systemic Mycoses

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

Opportunistic Mycoses

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

25

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

Innate

26

Who are at risk for fungal infections?

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

27

How else can fungi gain access to host tissues?

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

28

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.

Inoculum, Tissue Destruction, Multiply in tissues, Immunologic status

29

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

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

30

Main concern with antifungal drugs

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

31

Topical Therapy

Used for superficial/cutaneous infections

32

Systemic Therapy

Used for subcutaneous and systemic infections, some cutaneous

33

What are the most common targets of Antifungals?

Cell wall and Cell membrane

34

What two parts of cell wall synthesis are inhibited?

Glucan synthesis (by Echinocandins)

Chitin synthesis (by Nikkomycin)

35

What part of cell membrane synthesis are inhibited?

Ergosterol synthesis (by Azoles and Allylamines)

36

How do Polyenes act as Antifungals?

Bind to Ergosterol and disrupt fungal cell membrane

37

What drugs inhibit Ergosterol synthesis?

Azoles, Allylamines, Thiocarbamates, Morpholines

Mnemonic: "A lil ATM" --> Allyl ATM

38

What drug binds directly to Ergosterol?

Polyenes

39

Amphotericin B (Agent and Mechanism)

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

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

***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

Laboratory Diagnosis of Fungal Infections

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

42

KOH Preparation

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

All dyes tend to bind _____

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

All fungi stain ____

Gram Positive

45

When you see an India Ink Stain, think

Cryptococcus neoformans

46

Germ Tube Test

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

Examples of Fungal Lab Cultures

Sabouaud's dextrose agar
Cornmeal agar
Czapek Dox agar