Intro to Clinical Mycology Flashcards
What are three ways fungi can affect humans?
1) allergens
2) toxin producers (mycotoxins)
3) infectious agents (colonization)
What are saprophytes?
fungi that live on dead or decaying matter
Can fungi live symbiotically with humans (beneficial for both)?
yes
Is colonization required for allergens to infect humans?
no
What are peanuts constantly tested for?
aflatoxin that is toxic to humans
What are two important differences between fungal and human cells?
1) cell wall
2) membrane sterol composition
What sterol composition do fungal cell membrane have?
ergosterol
Why is it important to target fungal cell walls?
human cells do not have cell walls
What’s the function of fungal cell wall (4)?
1) shape
2) rigidity
3) strength
4) protection from osmotic shock
About 90% of a fungal cell mass is…
cell wall
What are the two fungal structures and classification?
1) yeast
2) mold
Is yeast unicellular or multicellular?
unicellular
Some fungi can grow as both yeast and molds, what is this called?
dimorphic
By what process do yeast reproduce in?
budding
What shape do yeast have?
spherical or ellipsoid shape
Fungal cell wall is primarily composed of all of the following polysaccharides except:
1) chitin
2) cellulose
3) chitosan
4) mannan
5) galactomannan
galactomannan
Molds grow through the development of ____
hyphae
What shapes do hyphae have?/
tube or ribbon shaped
Hyphae of most fungi have cross-walls which divide into segments called ____
septa
Under proper conditions some yeast form structures known as ____
pseudohyphae
Candida albicans (yeast) produces a structure known as a ____
germ tube
A mass of intertwined hyphae is called ____
mycelium
How do molds reproduce?
sexually or asexually
What type of mold reproduction produces conidia?
asexual
What type of mold reproduction produces spores?
sexual
Will you be able to tell the difference between bacteria and yeast macroscopically on an agar?
No, but definitely microscopically
What are the different types of fungal infections?
1) superficial mycoses
2) cutaneous mycoses
3) subcutaneous mycoses
4) systemic mycoses
5) opportunistic mycoses
Which type of fungal infection involves outermost layers of skin and hair?
superficial mycoses
Which type of fungal infection extends deep into the epidermis as well as invasive hair and nail infections?
cutaneous mycoses
Which type of fungal infections involve the dermis, subcutaneous tissues, muscle and fascia?
subcutaneous mycoses
Which type of fungal infections originate primarily in the lung but may spread to any organ in the body?
systemic mycoses
Which type of fungal infections associate primarily with immunosuppressed individuals?
opportunistic myscoses
Which immunity in healthy individuals is generally sufficient in preventing fungal infections?
innate
What are some things that innate immunity can provide in preventing fungal infections?
1) intact skin
2) pH
3) competition with normal bacterial flora
4) epithelial turnover rate
5) desiccated nature of the stratum corneum
6) mucous membranes - antimicrobial peptides, ciliated cells
What’s another way fungi can gain access to host tissues?
traumatic implantation or inhalation
Does adaptive immunity play a role in controlling and eliminating fungal infections?
cell mediated immunity is essential and most evidence supports that humoral immunity provides little support
The severity of fungal disease depends on what factors?
1) size of inoculum
2) magnitude of tissue destruction
3) ability of fungi to multiply in tissues
4) immunologic status of host
What are two types of therapy for antifungal drugs?
1) topical
2) systemic
Topical therapy is used to treat which type of fungal infections?
superficial and most cutaneous
Systemic therapy is used to treat which type of fungal infections?
subcutaneous and systemic infections and some cutaneous as well
The antifungal agents Azole, Allylamines, Thiocarbamates and Morpholines all target what in fungi?
inhibiting the synthesis of ergosterol
What specific polyene binds to ergosterol in fungal membranes?
Amphotericin B
How does Amphotericin B work?
disrupts fungal membrane by forming channels that lead to osmotic lysis
Echinocandins are what type of antifungal drugs?
inhibitors of beta-glucan synthesis
Echinocandins is mostly used to treat which fungal diseases?
Candida and Aspergillus
How are fungal infections frequently diagnosed?
direct visualization of fungal elements in infected tissues
Following cultivation, what are some ways to identify fungi?
colony morphology
hyphal and spore structures
Briefly describe how KOH prep work
KOH dissolves the skin, nail, or whatever human specimen and the leftover is fungi (human cells dissolves at a much greater rate than chitinous cell walls found in fungi)
Do fungi stain Gram (+) or (-)?
ALL fungi stain Gram (+)!!
What fungal organism should come to mind upon the mention of India Ink stain? Why?
Cryptococcus neoformans
It is a specific stain for their capsules!!
Germ tube test?
Candida albicans
How long does it take to culture fungi routinely?
3-4 weeks (very slowwww)
