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Flashcards in Intro to mycology Deck (21)
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1
Q

What is a fungus? Categories?

A

Eukaryotic kingdom. Few that cause disease. Larger than bacteria. Heterotroph, require preformed organic carbon. Mushrooms, yeast, mould

2
Q

Structural features

A

Chitin: Cell wall polysaccharide (mannan and glucan too), Distinguishes fungi from plant cells (cellulose), Adsorbs certain dyes, key identification feature; No cell wall in mammalian cells; Peptidoglycan is polymer in bacterial cell wall. Ergosterol: Cell membrane sterol (rigidity, Distinguishes fungi from mammalian cells (cholesterol) – Antifungal target

3
Q

Yeast general

A

Unicellular, round/ovoid, asexual budding. Yeast are normal GI flora. Genus of note is candida, cryptococcus, malassezia. Microscopy look different, look for structure. Plated cultures hard to tell apart from bac.

4
Q

Mould general

A

Filamentous fungi, multicellular, filamentous, branching growth. Hyphae/mecelia, growth at the hyphal tip -reproduce primarily by conidia: asweual spores, give mould its colour, easily airborne (transmit, allergy, etc). Humans have no endogenous mould. Microscopy look like dandelion. Plates look fuzzy.

5
Q

Superficial fungal diseases

A

aka cutaneous. The Dermatophytes have tropism for keratinized tissue – skin, hair, and nails; rarely invade deeper tissues. Athletes foot, ringworm

6
Q

Subcutaneous fungal diseases

A

Deep, ulcerated skin lesions. Nodules pop up. Rarely invade deeper tissues. Sporotrichosis (Sporothrix). Not many of these.

7
Q

Opportunistic fungal diseases

A

Not ‘true pathogens’, low virulence potential, Require immune compromise. ex. Aspergillus, Candida, Mucor, Cryptococcus

8
Q

Endemic fungal diseases

A

aka. Systemic/Dimorphic. ‘True pathogens’, cause severe disease in healthy people. Restricted geographically. Usually involve lungs, as well as deep organs via dissemination. ex. Histoplasma, Blastomyces, Coccidioides

9
Q

Human/fungi interaction.

A

Limited. Most like 25-30C and slightly acidic pH. Innate immunity prevents most growth unless you have deficiencies etc.

10
Q

Transmission methods of fungi

A

Inhalation — spores, conidia; Aspergillus, Endemic mycoses. Mucosal colonization – Candida. Skin break or injury – Candida, Sporothrix

11
Q

Immune regonition of fungi

A

Opsonins (comp, AB), PRR, TLR bind fungi. Activate phagocytosis, cytokines, resulting in ingestion or extracellular phagocyte killing

12
Q

Risk factors for invasive mycoses

A

Immunosuppression (Chemotherapy). Promotion of fungal colonization – Antimicrobial therapy. Direct access to blood, lungs, deep tissues – catheters, chemotherapy, Solid organ transplantation, Travel

13
Q

Patients at high risk for invasive fungal infection (IFI)

A

HSCT (blood stem cell recipient) - depends on how bad; SOT (solid organ transplant) - may depend on type of organ

14
Q

Diagnosing fungal disease

A

Specimen quality is very important. bronchial washing. Tissue or aspirate in sterile container. Not a lesion swab, sputum, stool (too much else going on). Microscopy (gram, silver) tells whether mould or yeast. Culture (yeast is smooth, round; and mould is fuzzy, filaments). Serology

15
Q

Pros of microscopy

A

Quick (same day), see unique cell features, some are quickly identified

16
Q

Pros and cons of culturing fungi

A

Confirms ID, usually unique features. Culture isn’t always positive, and it is slower (several days)

17
Q

Antigen detection for fungi

A

Some assays for antigens, but fairly limited.

18
Q

Serology for fungi

A

Look for AB, but usually there aren’t many. They general dono’t generate humoral response.

19
Q

Antifungal classes

A

Polyenes, azoles (targets cell membrane) , enchinocandins (targets cell wall), nucleoside analog

20
Q

Antifungal susceptibility testing

A

Test with broth microdilution (look at MIC); and disk diffusion (zone of inhibition). Determines if that anti fungal will be good or if they have resistance.

21
Q

Pulmonary Invasive aspergillosis

A

Mortality 50-100%. Persistent. Thermotolerant. Not responsive to antibiotics. Shows up at halo in lung. Can disseminate throughout bloodstream if they break out of alveoli.