Intro to Mycology

Question 1

Single cell forms of fungi are ____.

Answer 1

Yeasts

Question 2

Multicellular forms of fungi are ____.

Answer 2

Mold

Question 3

What are Spores?

Answer 3

sexual reproductive elements of fungi

Question 4

What are Conidia?

Answer 4

asexual reproductive elements of fungi

Question 5

Are fungi eukaryotic or prokaryotic?

Answer 5

Eukaryotic saprophytes (recycle organic matter for use)

Question 6

How do fungi differ from animal cells?

Answer 6

Cell wall made up of chitin and ergosterol in cell membranes (rather than cholesterol in animals)

Question 7

How is asexual reproduction of yeasts accomplished?

Answer 7

budding (blastoconidium)

Question 8

How is sexual reproduction of yeasts accomplished?

Answer 8

ascospores (spores that are surrounded by ascos)

Question 9

What is a mycelium?

Answer 9

intertwined mass of hyphae

Question 10

What is dimorphism?

Answer 10

a virulence factor for fungi in which they can change forms from mold to yeast to establish infection in humans. Yeast form in tissue and culture at 37C and mold form in environment and at room temp in culture. Yeast form is the invasive form

Question 11

What are some important dimorphic fungi?

Answer 11

Blastomyces dermatitidis
Coccidiodes immitis
Histoplasma capsulatum
Paracoccidiodes brasliensis

Question 12

Candida Albicans occurs in what form always?

Answer 12

yeast only (so is cryptococcus neoformans-capsulated and causes meningitis)

Question 13

Aspergilus fumigatus.

Answer 13

always a mold even when it establishes infection in the body (not really infection but just grows as mold)

Question 14

T or F. In general, fungi produce sub-acute, self-limiting infections.

Answer 14

T. and there are no known toxins involved in human infection unlike bacteria

Question 15

Opportunistic molds are sensitive to what part of human immunity?

Answer 15

Neutrophils

Question 16

Is most of the human response to fungi T-cell mediated or humoral in nature?

Answer 16

T-cell mediated

Question 17

How is microscopic diagnosis of fungi infection done?

Answer 17

tissue is treated with 10% KOH to dissolve any animal and soft tissue associated with the yeast and mold forms and the chitin wall of fungi cells remains and is visible.

Question 18

How is culturing diagnosis of fungi infection done?

Answer 18

done on Sabouraud’s medium which is high glucose and has a pH of 5.6 which favors fungi growth over bacteria growth. If the plate is incubated at 37C yeast would growth and if incubated at 25C molds would grow up. Molds are differentiated by morphology. yeast yield bacterial-like colonies.

Question 19

T or F. Antifungal are usually more toxic than antibacterial.

Answer 19

T. Due to similarities to humans . And the treatment regimens often last months due to slow growth of fungi

Question 20

What are the three major targets of antifungals?

Answer 20

Cell membrane (ergosterol),
cell wall, and
genome replication

Question 21

In general, how are localized or superficial/cutaneous fungal infections treated?

Answer 21

left to observation or topical creams

Disseminated infections are treated with Ampho B and/or AZOLES

Immunocompromised patients are left on AZOLES for life to limit recurrences

Question 22

Classification of fungi

Answer 22

Zygomycetes,
Ascomycetes (majority of human pathogens),
Basidiomycetes (Aspergilus),
Deuteromycetes (fungi imperfecti)-lack sexual stage

or

Superficial (least severe)
Cutaneous
Subcutaneous
Systemic (can disseminate in immunocompetent people-most virulent)
Opportunistic (most severe)

Question 23

Tinea (ringworm)

Answer 23

Involved skin, hair, and nails

Caustive agents are Dermatophytes. Three genera:
Epidermophyton
Microsporum
Trichophyton

Always molds

Dogs and cats are reservoir for infection

A single form of tinea can be caused by more than one dermatophyte and assigned dermatophyte can cause more than one tinea so we don’t typically look for a specific dermatophyte

Question 24

Tinea Capitis

Answer 24

tinea of the scalp- itchy and hair falls out

can be diagnosed using a Woods lamp

Question 25

Tinea Corporis

Answer 25

tinea on the body

Question 26

Subcutaneous mycoses

Answer 26

Example is sporotrichosis caused by sporothrix schenckii that is dimorphic and can borrow into deeper layers of dermis or bone

commonly found in soil or vegetation and the leaves and pedals of rose bushes

can’t penetrate epidermis unless break in skin

think rose bush prick

fixed and lymphocutaneous forms

Question 27

Systemic mycoses

Answer 27

often are endemic. Where person became infected is important

Three fungi:
Blastomycosis
Histoplasmosis
Coccidoidomycosis

Question 28

Where is Blastomycosis common?

Answer 28

East (MidSouth all the way up through Ohio and New York, and Minnesota into Canada)

Question 29

Where is Histoplasmosis common?

Answer 29

Southeast (Illinois, TN, AR, LA, GA, Kentucky)

mississippi and ohio river valleys

Question 30

Where is Coccidioidomycosis common?

Answer 30

Southwest (texas to southern CA)

san juaquin valley (called valley fever here)

Question 31

Histoplasmosis

Answer 31

inhalation of Histoplasma capsulatum confided

grows in soil containing bat or bird shit (common near Mississippi River)

H. capsulatum is dimorphic, converts to yeast forms in host that can replicate in macrophages by reducing acidification of phagolysosome or inhibits fusion of phagolysosome

80% of residents have been infected
95% asymptomatic or mild flu-like
5% result in a cute pneumonia
1% disseminate in macrophages, leading to short, and renal and hepatic failure

Question 32

Diagnosis of Histoplasmosis

Answer 32

• presence in endemic area
• treburculate macroconidia (bumpy surface) in mold or

yeast is isolated and budding yeast form inside macrophages can be diagnostic

Question 33

Opportunistic Mycoses

Answer 33

Candidias (thrush=overgrowth of candidia- seen in chemotherapy patients)