Fungi Flashcards
what do fungi have in their plasma membranes instead of cholesterol?
ergosterol
what kingdom are fungi from?
eukarya
what kind of fuel do fungi need to survive and what term defines that?
preformed organic energy supplying compounds, heterotrophic
what type of ribosomes and cell walls do fungi have?
chitin and beta glucan cell walls
80S ribosomes
what is a major barrier in antifungal treatment?
toxicity- fungi have more similar molecules to humans (few possible targets)
what are some differences in where fungi can live compared to bacteria? What implication does this have on where they grow
they can live in more extreme conditions- drier, higher osmotic pressure and colder
Tend to be more cutaneous infections and grow in refrigerated food
what are the two main types of fungi?
yeasts and molds
describe the structure of a mold.
mats (mycelia) of fibers (hyphae)
describe a yeast
a single celled fungus that reproduces by budding
describe the reproduction cycle of a fungus
very complicated reproduction pathways involving multiple forms of fungus and possibly different types of reproduction
what structure makes identifying fungi easier microscopically?
there are 5 types of asexual spores with distinct appearance. can help aid diagnosis
explain thermal dimorphism and what implications does it have for infection?
when a fungus grows at a mold at 24C and as a yeast at 37C- grow as yeasts in the body
what are the two hallmark immune responses to fungal infection?
granulomas and suppurative exudate (pus)
how are fungal pathogens transmitted and what implications does it have on treatment?
grow in the environment and cannot be passed from person to person
means there is little drug resistance but also infections cannot be eradicated
what type of yeast is normal flora?
C albicans
what is mycotoxicosis?
syndrome caused by eating fungal toxins (not a fungal infection)
what type of hypersensitivity response is common with fungal infections?
type 1 (allergies)
what skin test is used to diagnose fungal infection?
PPD type test
why is KOH added to fungal microscopy samples?
to kill all human cells
what medium is fungus cultured on?
Sabouraud’s agar
if a patient has a dangerous systemic fungal infection, what is the quickest way to diagnose it?
PCR amplification and molecular testing
What tests are used for systemic fungal infections?
PCR and serology
what are the major classes of antifungal agents?
polyenes, azoles and echinocandins
what is the mechanism of a polyene drug and what is the major type?
disrupt cell membrane at ergosterol insertion sites
Amphotericin B
what is the mechanism of azoles?
to inhibit ergosterol synthesis
what is the mechanism of echinocandins?
inhibits beta- glucan synthesis
what is the most effective broad spectrum antifungal class?
polyenes
why is amphotericin B only used in life threatening fungal infections?
it is nephrotoxic
what antifungal is approved for use on pregnant women with systemic fungal infection?
Amphotericin B
what are the two major Azoles and what fungi are they effective against?
Diflucan and Fluconazole
candidiasis and cryptococcosis
what is the major benefit of Echinocandins?
low toxicity
what fungal infections are Echinocandins effective against?
candida and aspergillus
which types of mycoses do not require thermal dimorphism?
superficial mycoses
what are the symptoms of superficial mycoses?
minor symptoms of itch and discoloration
what is used to treat superficial mycoses?
topical azoles or oral griseofulvin
treat all sites simultaneously
what is fungal infection of the skin called and which structures does it infect?
dermatophytosis
infects skin, hair and nails (keratinized structures)
what are the symptomes of dermatophytosis called and where are the major subtypes commonly called?
Tinea
jock itch, athlete’s foot and ringworm
how are tineas transferred?
fomite or autoinnoculation
how are dermatophytoses diagnosed?
KOH microscopy mount and culture
how is a subcutaneous mycosis contracted?
trauma exposing subcutaneous tissue to the environment (usually thorn pricks and splinters)
how do subcutaneous mycoses spread?
through the lymphatics towards the trunk
what is a common complaint that patients will have with subcutaneous mycoses?
ineffective treatment with antibiotics
how are subcutaneous mycoses treated?
oral azoles
serious cases- amphotericin B and local surgery
what is sporotrichosis and what organism is it caused by?
it is a subcutaneous mycosis caused by sporothrix spp
in what two cases can Sporotrichosis become a pulmonary infection?
if the patient has COPD or has been treated long term with corticosteroids
what is a potential consequence of sporotrichosis infection with an immunosuppressed patient?
dissemination and meningitis
how is sporothrix spp diagnosed?
biopsy and culture at room temp from pus
how does one contract a systemic fungal infection?
inhaling spores (not person-person transmissible)
what is the range of severity for a systemic mycosis?
asymptomatic clearance to death
a systemic mycosis may mimic what type of infection? How are they differentiated in terms of exposure
TB
exposed to american dirt, not foreign crowds
what is coccidioides and where is it endemic?
a thermally dimorphic fungus that can cause systemic infection. endemic to US southwest and latin america
how does coccidioides grow in the following types of weather and when is it transmitted to people?
Wet and Dry
Wet weather-grows mold
Dry weather- mold dries and arthrospores are released (infectious)
60% of coccidioides infections results in what?
asymptomatic or flulike clearance by innate immunity or containment by CMI
what are the two diseases caused by mild infection by coccidioides and what are they characterized by?
valley fever and desert rheumatism
pulmonary infection and erythema nodosum
what characterizes a severe coccidioides infection?
major pneumonia or dissemination in blood or by marophages
what are the risk factors for severe coccidioides?
old age, black or phillipino, late in pregnancy, immunocompromised and occupational exposure
when is coccidioides infection treated and how?
if predisposed to complications- oral azoles
meningitis- fluconazole
pregnant or disseminated- amphotericin B
the severity and disease caused by an opportunistic mycosis is majorly due to what factor?
the patient’s pre existing conditions
optimal treatment of an opportunistic infection does what?
treats the infection and the underlying condition
cryptococcus causes what type of infection?
opportunistic mycosis
what host characteristic allows an infection of cryptococcus?
reduced CMI
what routine bloodwork finding is characteristic of cryptococcosis?
normal results with no inflammatory markers
when do patients typically present for a cryptococcosis infection?
late in disease with meningitis and skin nodules or pulmonary symptoms
how is cryptococcosis diagnosed?
biopsy, CSF or crag (serotyping)
how is cryptococcosis treated?
a combination of azole and amphotericin B while treating the underlying condition
