Fungi Flashcards
2 Forms of Fungi
QUIZ/EXAM Q***
1) Yeast
-unicellular organism
-asexual reproduction, budding
2) Mold
-multicellular organism
-sexual reproduction
What reproduces more slowly?
a) yeast
b) mold
a) yeast
What is more difficult to treat?
a) yeast
b) mold
a) yeast
due to intrinsic resistance (property that doesn’t need to be learned or acquired)
Fungal characteristics (3)
1) contain membrane bound organelles
2) distinct organelles:
-Mitochondria (cell generator)
-Endoplasmic reticulum (manages cellular export)
-membrane bound nucleus
3) sexual and asexual reproduction
What is one of the biggest risk factors for fungal disease?
antibiotic use
Fungal Cell Wall
Ergosterol: similar to Cholesterol and is a primary sterol that makes up the cell wall
NO peptidoglycan
major structure: Chitin
exploited for diagnosis typically
new drugs use the cell wall as a target
Functions of the Fungal Cell Wall (3)
Ergosterol:
1) gives shape to the fungi
2) gives strength by protecting them from organic solvents and UV light
3) secretes enzymes from their walls - able to hydrolyze sugars for nutrition
Primary fungal reproductive structures
spores or conidia
can transmit spores, very bad for patients
Fungal reproduction is
a) fast
b) slow
b) slow
mold takes up to 6 weeks to grow in lab
yeast (unicellular) is a little quicker, 48 to 72 hours
Many medically relevant fungi are ____________
environmental
Medically relevant yeasts (2)
1) Candida app
2) Cryptococcus spp
Candida app
normal flora of the GI tract and often colonized the skin and the environment
leads to infections in immunocompromised to some degree
can lead to several aetiologies
-candidemia
-oral thrush - advanced immunocompromised (radiation, chemo, AIDS)
-vaginitis (most common)
-diaper rash
Risk factors for invasive Candida app infections (many)
critical illness
organ transplant
neonates
antibiotics*
total parenteral nutrition
hemodialysis
chemo
Cryptococcus spp
can lead to disease/ infection in those with altered immune status or underlying morbidity
environmental - found in soil and in dried animal faeces, specifically associated with bird poop or guano
can lead to pneumonia, fungemia (disseminated), cryptococcemia (meningitis) and cutaneous infection
contains large capsule around the yeast cell - helps it evade immune mediated phagocytosis
Most medically relevant Cryptococcus spp (2)
1) Cryptococcus neoformans
2) Cryptococcus gattii
Medically relevant molds (4)
1) Dermatophytes
2) Zygomycetes
3) Hyaline Molds
4) Dimorphic Fungi
Dermatophytes
distinct group of fungi that ONLY nail, skin, hair → use keratin as carbon source
produce keratinase which helps break down nail, skin, hair
3 different genus of Dermatophytes
1) Trichophyton - “Tri” - infects hair, skin and nails
2) Microsporum - infects skin and hair
3) Epidermophyton - infects skin and nails
Examples of Dermatophytes (many)
ringworm
Athlete’s foot
Tinea corporis (body)
Tinea pedis (foot)
Tinea capitis (head)
What is one of the few fungi that can infect an immunocompetent person?
dimorphic
Dimorphic fungi (6)
1) Histoplasma capsulatum
2) Blastomyces dermatiditis
3) Coccidioides immitis
4) Paracoccidiodes brasilensis
5) Sporothrix schleferi
6) Taloromyces marneffei
Histoplasma capsulatum
found around the world
clinical presentation include fever, sweats, weight loss, fatigue, and respiratory symptoms
CNS involvement in 5% to 20% of cases of acute disseminated histoplasmosis, presenting as chronic meningitis
disseminated disease are rare but seen
Blastomyces dermatiditis
Massachusetts, NY, Kingston, Northern Ontario, Montreal, St. Lawrence Valley
presents as nonspecific febrile acute or chronic pulmonary disease mimicking CAP and/or malignancy
ultimately to disseminated disease involving cutaneous, genitourinary, and bony lesions
Coccidioides immitis
pulmonary involvement and in most cases is asymptomatic
symptomatic infection presents with fever, cough, and chest pain and may mimic CAP
disseminated disease can occur locally with pleural or pericardial invasion or any organ of the body
disseminated disease can involves cutaneous, genitourinary, and bony lesions
Paracoccidiodes brasilensis
found in Brazil, South America
Sporothrix schleferi
likes plants, “rose grower’s” fungus on rose thorns
infection at the site
Taloromyces marneffei
exclusively in Southeast Asia - Vietnam, Laos,
Vietnam War - reactivates when you get immunocompromised
Temperature dependent dimorphism
2 different morphologies: yeast and mold
infects you as a yeast, found in the environment as a mold
yeast at 37C
mold at 25C
if it cannot live at that temperature, won’t infect you
Infection Classification (4)
1) Superficial or cutaneous mycoses
-e.g. dermatophytes - like skin, hair, and nails
-nail infections, dandruff, ringworm - break down keratin
2) Subcutaneous mycoses
-more embedded
3) Systemic mycoses
-in blood
-fungemia
4) Opportunistic
-immunocompromised
T or F: Most pathogens are opportunistic
TRUE
Opportunistic fungi definition/characteristics
immune system needs to be compromised
cause significant illness in the immunocompromised, those with prosthetic/IV devices and hematologic malignancies
molds - can result in sinus infections, respiratory diseases and fungemia
Opportunisitic fungi (5)
1) Aspergillus
2) Penicillium
3) Paeciliomyces
4) Acremonium
5) Fusarium
Most common invasive mold
Aspergillus
Aspergillus
has become the major cause of morbidity and mortality in immunocompromised patients
lung cancer, cystic fibrosis
almost 2/3s (61%) of patients with invasive aspergillosis have an underlying hematologic disease, or have undergone bone marrow transplantation
Zygomecetes (Mucorales) Molds
fast growing fungi
characterized by primitive coenocytic (mostly aseptate) hyphae
known as “lid-lifters” (2 days)
environmental - soil, dung and vegetative matter
extremely aggressive disease as the organism does not respect tissue planes including devastating rhino-orbital infections and wound infections
T or F: anti-fungals have more side effects compared to other medications like antibiotics
TRUE
Anti-fungal therapy effects (5)
effects:
1) Lanosterol synthesis
2) Ergosterol synthesis
3) Nucleic acid synthesis
4) Forms membrane pores
5) Cell wall synthesis
Lab detection of fungi
gram stain + additional stains from specimens - may see fungal elements
culture on specialize media:
-Yeast: 1-3 days
-Dermatophytes: 1-3 weeks
-Systemic fungi: 3-6 weeks
variety of stains used can help identify fungi
