Medical microbiology: fungi

Question 1

septae hyphae

Answer 1

45 degree angle and v shaped

Question 2

non septae hyphae (also rhizopus)

Answer 2

90 degree angle and grow at irregular right angels

Question 3

fungal cell wall

Answer 3

mannoproteins + beta glucans and chitin (polymer of NAG)

Question 4

fungal membrane

Answer 4

ergosterol

Question 5

fungal disease: mycoses in europe

Answer 5

yeast:
candida albicans
cryptococcus neoformans (bird faeces)

mould:
aspergillus fumigatus

Question 6

dermatophytosis = tinea/ringworm

includes:
athletes foot, jack itch, onychomycosis, tinea barbae + tinea corporis

Answer 6

superficial growing in moist places:
trichophyton
microsporum
epidermophyton

dandruff yeast = malassezia

Question 7

sporotrichosis = subcutaneous mycosis

dimorphic

Answer 7

sporothrix schenkii:
environment = mould
infecting humans = yeast

spreads along lymphatics

Question 8

mycosis yeasts: candidiasis

Answer 8

opportunistic in antibiotic use

systemic in debilitated or immunocompromised

3 common sites of infection:
oral
cutaneous
female genital

Question 9

mycosis yeasts: pulmonary candidiasis

Answer 9

gets out of control causing lesions in organs, blood infection

disseminates into the lungs

Question 10

mycosis yeasts: cryptococcus neoformans
dimorphic

mucacarmine red stain

Answer 10

inhaled and presents as meningitis in immunocompromised individuals

single cells yeast in humans
hyphal fungas in environment

titan cell: large equivalent to human micrphage
grows with capsule

can cause tissue destruction as a nodule

Question 11

mycoses mould: aspergillus fumigatus

Answer 11

remains a mould and grows hyphae at 45 degrees making spores

inhalation of spores causes pulmonary disease
can also infect wounds and burns

3 main types:
pulmonary
aspergilloma (pulmonary + post TB)
invasive aspergillosis (rare + immuncomporomised individuals i.e. opportunistic)

Question 12

histoplasmosis = dimorphic

Answer 12

bat + bird droppings along river valleys

inhalation of spores

causes acute pulmonary infection + inflammatory syndromes

treatment: amphotericin B or itraconazole

Question 13

blastomycosis = thermally dimorphic

Answer 13

similar to histoplasmosis

non specific flu like symptoms
asymptomatic in 50%
disseminated to skin and can infect bones + joints

treatment: amphotericin B or itraconazole

Question 14

coccidiomycosis = dimorphic

Answer 14

desert associated

inhilation of spores (septae) from soil and once inhaled they become spherules

when spherule ruptures its contents are released and it disseminates

causes: atypical pneumonia + flu like symptoms (valley fever)
treatment: resolves without treatment but can be chronic > 20 years as lung abscess

treatment in disseminated:
oral fluconazole
IV amphotericin

Question 15

cryptococcus gattii = dimorphic

Answer 15

associated with trees

causes pulmonary symptoms and respiratory issues

Question 16

anti fungal drugs

Answer 16

1. polyenes = depolarize the cell membrane
   amphotericin B
   targets ergosterol
   active against all fungi
2. azoles = prevent ergosterol synthesis by inhibiting cytochrome P 450 3A enzyme
   fluconazole (yeasts)
   voriconazole (aspergillus)
3. Glucan synthesis inhibitors
   weaken the cell wall
   echinocandins e.g. caspofungin