Fungi 1

Question 0

Antifungals

Answer 0

Target beta-glucan and ergosterol

Often have some toxicity in humans (many of molecules are too similar to ours)

Question 1

Fungi properties

Answer 1

Eukaryotic heterotrophs (cannot produce own energy)
No 70S ribosome nor peptidoglycan
Has cell wall of chitin, beta-glucan
Cell membrane has ergosterol instead of cholesterol
Can grow in drier, higher-osmotic-pressure and colder environments than bacteria
More cutaneous infections and food spoilage

Question 2

2 main types of fungi

Answer 2

Yeast: single-celled, reproduce by budding, new cells by closed mitosis

Molds: grow as hyphae (filaments) and mycelia (mat form), complex reproduction (mitosis, sexually or asexual spores [conidia; 5 types that have distinctive microscopic appearance that may be used for diagnosis])

Question 3

Thermal dimorphism

Answer 3

Several important fungal pathogens grow as mold at 24C and as yeast at 37C
Yeast form has more immune-evasive properties
Dual cultures can be useful for diagnosis

Question 4

Immune response to fungal infections

Answer 4

Granulomatous (collection of immune cells to wall off foreign substances), sometimes also suppurative (pus)

Question 5

Fungal pathogens

Answer 5

Most are environmental
Little contagion or drug resistance
No eradication
Exceptions: C. Alibicans yeast is normal flora/opportunistic pathogen

Question 6

Mycotoxicosis

Answer 6

Caused by eating fungal toxins (wrong mushroom or spoiled food), not fungal infection

Question 7

Fungal allergies

Answer 7

Can be dangerous, asthmatic reaction (brinchoconstriction mediated by IgE)

Question 8

Laboratory diagnosis

Answer 8

Diagnosed by PPD-type skin tests 
KOH mount microscopy with fungal stains 
Culture on Sabouraud's agar
PCR available for dangerous systemics
Serology for epidemiology

Question 9

Polyenes

Answer 9

Major class of antifungal agent

Disrupt fungal cell membranes at ergosterol insertion sites

Highly effective, broad spectrum but toxic

Amphotericin B is the only systemic one used, is nephrotoxic

Question 10

Azoles

Answer 10

Major class of antifungal agent

Inhibit ergosterol synthesis

Less toxic

Different ones optimally active against different fungi

Fluconazole/Diflucan major one that treats candidiasis and cryptococcosis (infections)

Question 11

Echinocandins

Answer 11

Major class of antifungal agent

Inhibit beta-glucan synthesis

Low-toxicity

Highly effective against candida and aspergillus