MYCOLOGY 4 - MEDICAL MYCOLOGY

Question 1

what is the angel death mushroom and what does it do?

Answer 1

amanita and galerina (basidiomycota - agaricomycetes)
both found in quebec
contain cyclopeptide toxins: amatoxins
accumulates in the liver, cannot make proteins, liver failure
heat stable, not affected by drying
the lethal dose is 0.1mg/kg and there is up to 15mg in the cap
inhibitor of RNA polymerase type II

Question 2

what are the compounds that cause psychoactive intoxications?

Answer 2

psylocybin and psylocin
produced by numerous fungi
used by many ancient civilizations
stoned age theory: people smoked the mushrooms, the brain had to get bigger to adapt and humans evolved to homo sapiens

Question 3

what does psilocybin act upon?

Answer 3

agonist at cortical serotonin 5-HT2A receptor
structure very similar to serotonin
used in clinical trials to treat PTSD and depression

Question 4

what is an example of a psychoactive intoxication?

Answer 4

the ergot fungus (ascomycota, sardoriomycete)
the host for this fungus is the rye plant
Lysergic acid (from fungus) + diethylamine makes LSD
there is a connections between the salem witch trials, rye and high humidity
the women might have just been intoxicated with fungus and killed for being weird

Question 5

how was Scheele’s paint a way to kill by collateral intoxication?

Answer 5

Scheele’s green bioremediation was used everywhere and napoleon loved it
the paint is made of cupric arsenite (copper + arsenic)
in paint, it is harmless unless you swallow it
an ascomycota-sardoriomycete fungus takes up to oxygen and releases the trimethylarsine as a gas, which is deadly when inhaled
green paint+fungus=poison

Question 6

what are some health benefits that can be derived from mushrooms (secondary metabolites)

Answer 6

• relieve joint pain, arthritis
• sunscreen
• smoke to relieve headache
• prevent/stop nosebleeds
• eye drop solutions

Question 7

what are the two types of infections?

Answer 7

superficial and invasive
superficial;
most common, often benign
frequent in immunocompetent individuals
easily treatable
example: ringworm
invasive:
rare and lethal if untreated
mostly in immunocompromised patients
example: mucormycosis

Question 8

what are superficial infections provoked by?

Answer 8

provoked by dermatophytes which feed on keratin
tinea unguium:
on the nail
5-10% of population
difficult to get rid of
3-6 months oral antifungals
onychomycosis

tinea pedis:
most common fungal infection in humans
up to 70% of all tinea
topical antifungal for 10-14 days, common recurrence

sources: anthropophile, zoophile or geophile

Question 9

how does candida albicans work?

Answer 9

three forms
yeast (okay)
pseudohyphae
true hyphae (invasive)
lives in Gi tract, mouths, vaginal flora
the morphological switch is required for virulence and not completely understood

Question 10

what are the three classifications of invasive infections?

Answer 10

yeasts:
systemic, pulmonary disease absent or subclinical
molds:
primary pulmonary disease with dissemination less common
dimorphic fungi:
primary pulmonary disease with dissemination being a prominent part of the disease

Question 11

what is an example of an invasive yeast infection?

Answer 11

candidemia
reaches blood flow and accesses different organs
affects immunocompromised patients
fatal if untreated
average mortality rate is 20-50%
average stay at the hospital is 2-8 weeks

Question 12

how do cryptococcus sp. infections work?

Answer 12

basidiomycota
yeast encapsulated in sugars
two common: C.neoformans and C.gattii
environment: soil, eucalyptus trees, bird droppings
acquired by breathing in the yeast or the spore
immunocompromised and competent both at risk
pulmonary infection often misdiagnosed, asymptomatic in 25-50% of cases
patients need to have a CSF puncture
creates a white spot in the lung

Question 13

how is cryptococcal meningitis treated?

Answer 13

in HIV positive patients, 80% of CSF cultures are positive for cryptococcus
the fungus is kicked out of the lung by the macrophages but then it goes to the brain and you die
treated:
induction: 1 week with amphotericin B
consolidation: high dose of fluconazole
maintenance: low dose fluconazole for a year
mortality rate is 50%

Question 14

cryptococcus gatti characteristics?

Answer 14

very rare
less than 300 human cases
less than 400 animal cases
appeared in 1999
pneumonia and meningitis in immunocompetent patients
infects native trees and soil

Question 15

characteristics of mold infections

Answer 15

majority are opportunistic, very aggressive and destructive

Question 16

what is the most common mold infection

Answer 16

aspergillus
aspergillus fumigatus is the most common species (ascomycota)
disease: invasive pulmonary aspergillosis

Question 17

how does aspergillus fumigatus spread?

Answer 17

conidiospores make conidia: asexual spores
we breathe in dozens of conidia every day
in healthy individuals those spores are eliminated by the immune syctem

Question 18

how does aspergillus fumigatus infect?

Answer 18

infects both immunocompromised patients or patients with impaired lung function
alveolar infection: goes into the first layer of cells
angioinvasion: goes deeper
lung propagation: travels through the lung
in immunocompromised patients this leads to invasive pulmonary aspergillosis
in patients with bad lung function this leads to chronic aspergillosis

Question 19

characteristics of dimorphic fungi (endemic mycoses)

Answer 19

infect immunocompetent individuals
geographically restricted in range
classically dimorphic: environmental mycelium form vs infecting yeast form

Question 20

how does blastomyces dermatidis work?

Answer 20

in the environment:
25°C
saprophytic mycelium forming microconidia
found associated with wood, major dog pathogen
endemic region: great lakes and mississippi valley
in the human body:
37°C
parasitic yeast
lung infection
dissemination to the blood and ultimately other organs
cutaneous secondary infections are frequent
low mortality