Medical Mycology Flashcards
what are negative effects of fungus?
- crops economogy
- asthma irritation of fungal spores
- infect many tissues
what are mycoses?
infection caused by fungus
what are mycotoxins?
apart from invasive mycoses, fungi release toxins in food and airborne
jobs that disrupt environment…
increase chances of fungal infection
the burden of fungal disease compared to malaria?
much less
what is transient exposure?
fungal colonization on skin (occurs without host knowledge)
most fungi have…
low virulence
why is it difficult to diagnose fungal infection?
similar symptoms to bacteria and viruses = misdiagnosis
what are the ways of classifications of mycoses?
- site of infection
- route of acquision (exogenous:environement/endogenous: commensal)
- type of virulence
what are potential sites of infection for mycoses?
- superficial (skin surface)
- cutaneous (epidermis layer)
- subcutaneous (wound in dermal layer)
- systemic (bloodstream)
all besides systemic can clear on its own
what are Types of fungal virulence
- primary mycoses (uncommon, healthy)
- opportunistic mycoses (immunocompromised, common)
superficial and cutaneous mycoses are caused by
dermatophytes
dermatophytes infections are caused by – in the genera
molds
trichophyton, microsporum, and epidermophyton
dermatophytes infections are usually—
self-liming with no ceppular immune response bc superficial and not much redness
what is the dermatophytes fungi treatment?
topical antifungal drug or in sever cases, oral drugs
examples of dermatophytes infections?
athletes foot and ringworm
what are common types of opportunistic fungal pathogens?
- Candida budding yeasts with haephal projections
- Aspergillus mold spores
risk factors for fungal infection?
- HIV/AIDS infection
- solid organ transplants (suppress immunity meds)
- cancer chemo
- granulocytopenia: deficient in neutrophils
- premature birth
- old age (defective immunity)
- corticosteroid use (suppress immunity)
- broad spec antibiotics (kills good and bad bacteria)
- certral vascular catheters
- gasterointerestinal surgery (contaminated tools)
- colonization with fungus (recurrent)
CCCGGPOOHA
Where can Candidiasis species be found?
innocuous carrying on skin/epithelial surfaces
What is the most infectious Candidasis species?
Candidiasis albicans
Types of Superficial candidiasis infections? characteristics of each?
oropharyngeal candidiasis
- oral, breastfed infants, ORAL thresh
denture stomatitis
- ulcers in mouth - elderly detures
vulvovaginal candidiasis
- antibiotic use
chronic mucocutaneous cadidiasis
- recurrent
virulence factors of candida?
- adhesins (attach to epithelial cells)
- dimorphism
- phenotypic switching (discrete change colour and protein)
- extracellular hydrolases (proteins that host cells have to prevent attack)
how does candidiasis become invasive?
- budding yeast form
- adhere to epithelial cells and dimorphism
- hyphael projections invade epidermis
- enter blood stream
Candida diagnosis?
- culture medium inoculum (swab skin and blood)
- detect anti-candida antibodies and antigens in blood
- DNA fingerprinting, micoarrays, PCR to see if endemic region
what type of fungus is Aspergillus? where is it found
filamentus, saprophytic fungus always present in environment
found in decaying vegetation and soil
common infectious ASPERGILLOSIS in humans?
Aspergillus fumigatus
CONIDIA OF ASPERGILLUS? immune response?
A. fumigatus conidia (spores) in air and inhaled and penetrate lower Respiratory tract
- Immunocompetent individuals: conidia are detected and destroyed by alveolar macrophages
- Immunocompromised individuals: spores settle, germinate, and invade, (invasive aspergillosis)
virulence factors of aspergillus?
- thermal tolerance (cold and fever)
- proteinase production (degrades extracellular matrix)
- gliotoxin production: causes apoptosis due to toxins
- environmental stress resistant (pH, salt, temp)
steps for aspergillosis invasion in blood stream?
- spores inhaled to lungs
- spore on surface of cell
- hyphael projections allow entry past alveolar cells from dimorphism
- dissemenation in blood
asperogilliosis symptoms?
- high mortality rate ( >50%)
- recurrent, hard to get rid of
- nonspecific fever, chest discomfort, cough with blood
asperogilliosis diagnosis?
- histopathological analysis
- culure of biopsy bronchoalveolar lavage fluid taken from the infected area of the lung post mortem
cloudy lung xray
what are endemic systemic mycoses?
targets immunocompetent
primary pathogens
covers a lot of the globe
have dimorphic switch (yeast or filamentous)
why are antifungal agents difficult to make?
fungus similar to humans
3 types of antifungal agent targets?
- plasma membrane
- cell wall
- nucleic acid/protein synthesis
How is Plasma Membrane targeted by antifungal agents?
- polyenes: binds to ergosterol and removes from plasma membrane
- azoles: targets ergosterol producing enzyme
How is Cell Wall targeted by antifungal agents?
- echinocandins: targets B-glucans - chitin binders
- nikkomycin: targets chitin production
How is Nucleic Acid and Protein Synthesis targeted by antifungal agents?
- 5-flurocytosine: uptake and cell turns it to 5’UTP used in RNA/DNA synthesis and disrupts
- sordarin: protein synthesis by targeting tRNA
what is combination therapy for antifungal agents?
combination of fungicidal and static (slow growth) drugs (helps for resistance)
what are the challenges of getting rid of fungal infection?
- early diagnosis
- limited antifungal drugs
- cytotoxicity (harmful off target effects to host)
- antifungal resistance
- emerging pathogens
