Fungi

Question 1

Fungi

Answer 1

eukaryotic heterotrophs, does not have 70S ribosome or peptidoglycan

Question 2

Antifungal

Answer 2

target beta-glucan, ergosterol, some toxicity to humans since there are fewer molecular targets available

Question 3

Fungi can grow in

Answer 3

drier, higher-osmotic-pressure, colder environments than bacteria leading to more cutaneous infections and food spoilage

Question 4

Two main types of fungi

Answer 4

yeast are single celled and reproduce by budding. molds grow in hyphae/mycelia and have complex reproduction. both make new cells by fungal mitosis; yeast and some others have closed mitosis.

Question 5

asexual spores

Answer 5

five types of asexual spores have distinctive microscopic appearances, used for diagnosis

Question 6

thermal dimorphism

Answer 6

can 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 7

immune response to fungal infection

Answer 7

granulomatous, sometimes also suppurative (discharge of pus)

Question 8

fungal pathogens

Answer 8

most are environmental, little contagion or drug resistance, no eradication

Question 9

mycotoxicosis

Answer 9

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

Question 10

fungal allergies can lead to

Answer 10

asthmatic reaction

Question 11

fungal infection

Answer 11

diagnosed by PPD, KOH-mount microscopy with fungal stains, culture on Sabouraud’s agar, PCR available for dangerous systemics, serology for epidemiology

Question 12

Major classes of antifungal agents

Answer 12

polyenes (distrupt fungal membranes at ergosterol insertion sites), azoles (inhibit ergosterol syn), echinocandins (inhibit beta-glucan syn)

Question 13

Polyenes

Answer 13

highly effective and broad spectrum but toxic - Amphotericin B is the only systemic and is nephrotoxic

Question 14

Azoles

Answer 14

less toxic, different ones optimally active against different fungi, fluconazole/diflucan major one, treats candidiasis and cryptococcosis

Question 15

Echinocandins

Answer 15

low toxicity, highly effective against candida and aspergillus

Question 16

Superficial Mycoses

Answer 16

Caused by fungal growth on the superficial skin layer, Does not require thermal dimorphism, Very common, but symptoms are minor: itch or discoloration, Treated with topical azoles, alt oral griseofulvin

Question 17

Dermatophytosis

Answer 17

is very common, caused by three different genera of fungi, infect only superficial keratinized structures, produce keratinases, symptoms are called Tinea (jock itch, athlete’s foot, ringworm). Transmitted by fomites or autoinnoculation. Diagnose by KOH mount, culture. Treat all affected body sites simultaneously w/ topical antifungal cream, alt oral griseofulvin.

Question 18

Subcutaneous Mycoses

Answer 18

Introduced by trauma exposing subcutaneous tissue to soil or vegetation, Slow spread from trauma site toward trunk by lymphatics, Thermal dimorphism, history of ineffective antibiotic treatment, Treated with oral azoles, In serious cases, amphotericin B and local surgery

Question 19

Sporotrichosis

Answer 19

is caused by Sporothrix spp, thermally dimorphic fungi of vegetation that enters skin through small injuries (thorns, splinters). Painless ulcer at site spreads up lymphatic over years. If COPD, may be pulmonary. If immunosuppressed, may be disseminated, meningitis. Diagnose by biopsy and culture at room temp from pus. Treat normal type with oral azoles, more serious forms with Amphotericin B.

Question 20

Systemic mycoses

Answer 20

Environmental: spores/fungi in soil, Inhaled into lungs, Thermal dimorphism, Range of severity: asymptomatic clearance to death, NOT person-to-person transmissible, may mimic TB, but source is American dirt, not foreign crowds

Question 21

Coccidioides

Answer 21

thermally dimorphic (mold/spherule), endemic to US Southwest, mold grows in wet weather, releases infectious arthrospores in dry, spores inhaled, change form. 60% Mild: asymptomatic or flulike clearance by innate or containment by CMI, Moderate: valley fever/ desert rheumatism: pulmonary+EN, severe: major pneumonia or dissemination (either bare or in macrophages). Risk factors: age, race, pregnancy, immunocompromise, occupational high exposure. Diagnose by exam, history, PPD, biopsy for spherules, culture, serology for dissemination. Treat if predisposed to complications (oral azoles), meningitis (fluconazole), pregnant or disseminated (Amphotericin B).

Question 22

Opportunistic mycoses

Answer 22

Diseases and severity are widely varied, depending on the patients’ pre-existing conditions, Optimal treatment addresses both the infection and the underlying problem

Question 23

Cryptococcosis

Answer 23

is environmental, enabled by reduced CMI, suppresses host inflammatory response. Presents late in disease with meningitis and skin nodules or pulmonary symptoms. Diagnose by biopsy, CSF, crag. Treat with combinations of azoles and Amphotericin B.