Fungal Pathogens

Question 1

what are saprophytic fungi useful for?

Answer 1

degrading and recycling organic matter e.g. lignin and cellulose

Question 2

what do phytopathogens cause?

Answer 2

rusts, smuts, rots, blights, mildews, galls and wilts

Question 3

what is mycology?

Answer 3

the study of fungi

Question 4

what is medical mycology?

Answer 4

the study of fungi pathogenic for humans

Question 5

what type of cell are yeasts?

Answer 5

unicellular fungi, usually oval or round

Question 6

how do yeasts reproduce?

Answer 6

by budding

Question 7

how do moulds grow?

Answer 7

as filaments or hyphae

Question 8

what is a mycelium?

Answer 8

a mass of hyphae

Question 9

what does it mean fungi are dimorphic?

Answer 9

they can grow as yeasts or hyphae

Question 10

are fungi eukaryotic or prokaryotic?

Answer 10

eukaryotic

Question 11

other characteristics of fungi?

Answer 11

1. non-motile
2. non-photosynthetic
3. have rigid cell walls

Question 12

what are the causative agents and mycosis of superficial mycosis?

Answer 12

Malassezia globosa - tinea versicolor

Candida albicans - candidosis

Question 13

what are the causative agents and mycoses of cutaneous mycosis?

Answer 13

Trichophyton spp. (Dermatophytes) - Athletes foot, ringworm

Question 14

what are the causative agents and mycosis of subcutaneous mycosis?

Answer 14

Sporothrix - sporotrichosis

Question 15

what are the causative agents and mycosis of systemic mycosis (primary, endemic?

Answer 15

Histoplasma capsulatum - Histoplasmosis

Question 16

what are the causative agents and mycoses of opportunistic mycosis?

Answer 16

Candida albicans - candidosis
Aspergillus fumigatus - aspergillosis
Cryoptococcus neoformans - cryptococcosis

Question 17

what is Pityriasis versicolor?

Answer 17

a superficial infection caused by Malassezia species, usually M. globes (M. furfur)

Question 18

how does yeast reproduce in pityriasis versicolor?

Answer 18

by hyphae

Question 19

does dermal penetration occur in pityriasis versicolor?

Answer 19

No

Question 20

risks factors of pityriasis versicolor?

Answer 20

endogenous or exogenous corticosteroids seen in normal individuals; climatic factors or sun exposure

Question 21

pityriasis versicolor’s symptoms

Answer 21

asymptomatic or mildly pruritic with scaling; confluent macule on the trunk, upper arms, or neck - these may be hypo pigmented or hyper pigmented

Question 22

what is the most prevalent in superficial candida infections?

Answer 22

oral and vaginal ‘thrush’ and denture stomatitis

Question 23

how do you treat superficial candida infections?

Answer 23

anti fungal treatment and treat predisposed factors (e.g. diabetes) and remove gut reservoir

Question 24

what are dermatophytes?

Answer 24

septate branching hyphae

Question 25

what is sporothrix schenkii?

Answer 25

chronic cutaneous or lymphocutaneous disease

Question 26

how does the person gets sporothrix schenkii?

Answer 26

fungal spores enter through abrasions

Question 27

what are primary pathogens?

Answer 27

mould and yeast

Question 28

when are mould and yeast pathogenic?

Answer 28

in the environment and in tissue

Question 29

how are systemic infections geographically restricted?

Answer 29

mostly in the USA, Central and South America

Question 30

species associated with disease in systemic infections?

Answer 30

Histoplasma capsulatum, Blastomyces dermatitis, Coccidioides immitis

Question 31

what enhances the growth of histoplasma?

Answer 31

by bird or bat excreta

Question 32

how do yeasts remain in the lungs in histoplasma capsulate?

Answer 32

yeasts remain viable (latent - sub clinical) in lungs for years

Question 33

what are opportunistic fungal infections?

Answer 33

most serious fungal infections worldwide

Question 34

are opportunistic fungal infections geographically restricted?

Answer 34

No

Question 35

what causes opportunistic infections?

Answer 35

candida, aspergillus and crytococcus species

Question 36

what to opportunistic infections infect?

Answer 36

hosts with impaired defences

Question 37

recognised risk factors included in opportunistic infections

Answer 37

• malignant disease, AIDS, burns, major surgery
• organ or bone marrow transplants
• antibiotic therapy, immunosuppressive therapy
• indwelling catheters

Question 38

how are systemic candida infections?

Answer 38

many are endogenous, and some (e.g. bloodstream) are exogenous

Question 39

where are aspergiullus infections found?

Answer 39

in air and soil, but not part of normal flora of humans

Question 40

what do A.fumigatus produce?

Answer 40

aerial hyphae bearing conidia (spores)

Question 41

what destroys inhaled conidia?

Answer 41

macrophages

Question 42

process of the activity of host defences against Aspergillus?

Answer 42

1. inactive conidia are inhaled
2. conidia lodge in lower respiratory tract
3. conidia swell
4. blocked by macrophages
5. conidia germinate into hyphae
6. blocked by neutrophils
7. hyphae invade tissues
8. blocked by neutrophils
9. hyphae invade blood vessels and disseminate

Question 43

what is cryptococcus neoformans?

Answer 43

yeasts with a thick polysaccharide capsule

Question 44

what happens during the infection of c. neoformans?

Answer 44

the polysaccharide is solubilised

Question 45

what is cryptococcal meningitis?

Answer 45

localised in brain and CNS

Question 46

how do agents have to be for anti fungal chemotherapy?

Answer 46

must be selectively toxic (more difficult with eukaryotic micro-organisms)

Question 47

what are Amphotericin B or fluconazole used to treat?

Answer 47

treating systemic infections