Mycology II

Question 1

What is the form of nutrition of most fungi?

Answer 1

saprophytic or parasitic to plants

Question 2

Do fungi infect humans and animals?

Answer 2

chance event, only occuring when conditions are favorable.

Question 3

Most fungi are what type of pathogens? What is the exception?

Answer 3

opportunistic pathogens!
exception: primary pathogens causing systemic mycoses and dermatophytes –> dimorphic fungi

Question 4

What yeastst have adapted to human and animal environments?

Answer 4

Candida and Malassezia

Question 5

What determines if a fungal infection will cause a disease?

Answer 5

the complex interplay between fungal virulence factors and host defense factors

Question 6

What does infection depend on?

Answer 6

• inoculum size
• the general immunity of the host.

Question 7

What are the virulence factors allowing for fungal pathogenicity?

Answer 7

• Ability to adhere to host cells by way of cell wall glycoproteins.
• Production capsules allowing them to resist phagocytosis.
• Ability to acquire iron from red blood cells as in Candida albicans.
• Ability to damage host by secreting enzymes such as keratinase, elastase, collagenase.
• Ability to resist killing by phagocytes as in dimorphic fungi.
• Ability to secrete mycotoxins.

Question 8

What are teh two forms of host defence factors?

Answer 8

1) Physical barriers, such as skin and mucus membranes
2) Chemical barriers, such as secretions, serum factors

Question 9

State examples of host defence factors.

Answer 9

Physical barriers = SKIN & MUCOUS MEMBRANES
The fatty acid content of the skin
The pH of the skin, mucosal surfaces and body fluids
Epithelial cell turnover
Normal flora

Chemical barriers = SECRETIONS AND SERUM FACTORS
Most fungi are mesophilic and cannot grow at + 37 C.

Question 10

At what temperature is it difficult for fungi to grow at?

Answer 10

37C+

Question 11

What is the professional name used to describe a fungal disease?

Answer 11

mycoses

Question 12

Many fungal infections of the skin involve what type of fungi?

Answer 12

fungi that are found in the normal skin microbiota.

Question 13

When can fungi that are found in the normal skin microbiota cause an infection?

Answer 13

when they gain entry through a wound

Question 14

How do fungi usually cause opportunistic infections?

Answer 14

in immunocompromised patients

Question 15

What type of environments promote fungal growth?

Answer 15

moist

Question 16

What are mycoses?

Answer 16

fungal infections

Question 17

How are mycoses classified?

Answer 17

based on their invasiveness:
- cutaneous mycoses
- subcutaneous mycoses
- systemic mycoses

Question 18

What are cutaneous mycoses?

Answer 18

Mycoses that cause superficial infections of the epidermis, hair, and nails.

Question 19

What are subcutaneous mycoses?

Answer 19

Mycoses that penetrate the epidermis and the dermis to infect deeper tissues.

Question 20

What are systematic mycoses?

Answer 20

Mycoses that spread throughout the body.

Question 21

What are cutaneous mycoses called tineas caused by?

Answer 21

dermatophytes (that require keratin, a protein found in skin, hair, and nails, for growth.)

Question 22

What are the three genera of dermatophytes which cause cutaneous mycoses?

Answer 22

Trichophyton,
Epidermophyton,
Microsporum.

Question 23

What is the favorable environments of dermatophytes?

Answer 23

• moist
• dark

Question 24

What causes aspergillosis? What is it?

Answer 24

A fungal disease caused by molds of the genus Aspergillus.
- primary: less common: begins in skin
- secondary: more common: beings in the respiratory system
- result: distinctive eschars that form at the site or sites of infection
- COMMON HOSPITAL AQUIRED INFECTION

Question 25

What do yeasts of the genus Candida cause?

Answer 25

opportunistic infections of the skin called **candidiasis**, producing intertrigo, localized rashes, or yellowing of the nails.

Question 26

What are the infections called when they are caused by fungi which invade immunosupressed hosts?

Answer 26

opportunistic infections

Question 27

What diseases are marked by respiratory distress?

Answer 27

Cryptococcosis(Cryptococcus), Histoplasmosis (Histoplasma)

Question 28

What yeasts cause skin infections referred to as cutaneous candidiasis?

Answer 28

Candida albicans and other yeasts in the genus Candida.

Question 29

What is 'intertrigo"?

Answer 29

A general term for a rash that occurs in a skin fold, or other localized rashes on the skin.

Question 30

How is Candidiasis of the skin and nails is diagnosed?

Answer 30

- clinical observation - culture, - Gram stain, - KOH wet mounts. - susceptibility testing for anti-fungal agents

Question 31

What type of mycoses can spreak from the skin to deeper tissues?

Answer 31

cutaneous mycoses are superficial, subcutaneous mycoses.

Question 32

In temperate regions, what is the most common subcutaneous mycosis? What is it caused by? How can it be avoided?

Answer 32

**sporotrichosis**, --> fungus Sporothrix schenkii - commonly known as rose gardener’s disease or rose thorn disease. - ontracted after working with soil, plants, or timber, as the fungus can gain entry through a small wound such as a thorn-prick or splinter. - avoided by wearing gloves and protective clothing while gardening and promptly cleaning and disinfecting any wounds sustained during outdoor activities.

Question 33

What is a ringworm?

Answer 33

Ringworm is an infection of skin, hair, or claws caused by a type of fungus.

Question 34

How is ringworm spread?

Answer 34

Most cases of ringworm are spread by contact with infected animal or contaminated objects such as furniture or grooming tools.

Question 35

Does contact always result in infection?

Answer 35

no!

Question 36

Where do dermatophytes grow? Where does the infection stop?

Answer 36

- grow only in the dead cells of skin and hair - infection stops on reaching living cells or inflamed tissue

Question 37

Can dermatophytes colonize the cornified structures (hair, claws) and the stratum corneum and cause disease without ever entering living tissue?

Answer 37

yes!

Question 38

Whet are the most contageous fungal infections caused by?

Answer 38

dermatophytes

Question 39

What environments do dermatophytes favour?

Answer 39

hot and humid

Question 40

What animals are more succeptible to dermatophyte infection?

Answer 40

- animals kept in overcrowded, dirty, or damp areas, - animals with inadequate nutrition, - immunosuppressed animals.

Question 41

What is the principal way of resolving an infection?

Answer 41

cell-mediated immune response.

Question 42

Dermatophytosis is caused by fungi in what genera?

Answer 42

Microsporum, Trichophyton and Epidermophyton.

Question 43

What type of pathogens (animal or human) are dermatophytes?

Answer 43

Microsporum, Trichophyton = Animal pathogens Epidermophyton = Human pathogen

Question 44

How are dermatophytes classified?

Answer 44

- Zoophilic - Anthropophilic - Geophilic

Question 45

Where are zoophilic dermatophytes mainly found?

Answer 45

in animals but can be transmitted to humans.

Question 46

Where are anthropophilic dermatophytes mainly found?

Answer 46

in humans and are very seldom (rarely) transmitted to animals.

Question 47

Where are geophilic dermatophytes mainly found?

Answer 47

in soil, where they are associated with decomposing hair, feathers, hooves and other. - infect both humans and animals

Question 48

What does 'endothrix' refer to?

Answer 48

dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell.

Question 49

What does 'exothrix (ectothrix)' refer to?

Answer 49

A dermatophyte infection which remains confined to the hair surface.

Question 50

What is the shape of Trichophyton and Microsporum

Answer 50

Trichophyton- cylinder Microsporum- spindle

Question 51

What is the main reservois for microsporum canis? Can it be transmitted to humans? How?

Answer 51

- cats and dogs - can also be transmitted to humans through direct and indirect contact with animals and fomites such as combs, brushes, hats, furniture, linens etc. - Microsporum canis can infect all mammals.

Question 52

How does Microsporum canis reproduce?

Answer 52

two conidial forms, 1) large, spindle-shaped, multicell macroconidia 2) small, single celled microconidia.

Question 53

What does microsporum canis produce?

Answer 53

- septate hyphae, - macroconidia, - microconidia.

Question 54

On what media does Microsporum canis grow?

Answer 54

Sabouraud dextrose agar - +25°C - 7 days - no specific growth factor or nutrition requirements (grows well on most commercially available media)

Question 55

What is the shape of Microsporum canis?

Answer 55

Macroconidia: - spindle-shaped, - asymmetrical apical knob. - 6- to 15-celled, long, - rough - thick outer cell walls. - thin septal walls Microconidia: - rare, - unicellular - clavate/pyriform

Question 56

What animals are susceptible to dermatophytes?

Answer 56

all domestic animals! * Dogs and cats * Cattle * Sheep and goats * Horses * Swine * Rodents, rabbits * Birds

Question 57

What is the incubation period of dermatophytes?

Answer 57

7 days to 4 weeks (cultivation at room temperature)

Question 58

Where do dermatophytes only grow in humans?

Answer 58

only in keratinized tissues

Question 59

What are the clinical signs of dermatophytes?

Answer 59

Alopecia Scaling, crusts Erythema, pruritus “Ringworm” appearance uncommon

Question 60

State the main fungus genera and species of animal dermatophytes diseases.

Answer 60

Dogs, Cats: Microsporum canis Horses: Trichophyton equinum Cattle: Trichophyton verrucosum Birds: Trichophyton gallinae

Question 61

What is often used to diagnose tineas (eg. microsporum)?

Answer 61

Wood's lamp - 'black lamp' - wavelength of 365nm