(O) 32: Mycology II Flashcards
Light vs Dark side of fungi
Light side
- food: agriculture, food production
Dark side
- agriculture (can affected food security, economic losses for farmers, can lead to famine)
- breathing in spores from fungi (can aggravate resp. conditions like asthma)
Mycoses
fungi (yeast or mold) that infect us
Fungi threats to health
- Invasive mycoses
- could also produce mycotoxins in food and airborne fungal spores (can cause asthma, hay fever, and other occupational diseases)
Fungal virulence
- fungal colonization can occur w/o the knowledge of the affected individual
- most fungi have LOW VIRULENCE
- difficult to diagnostically distinguish btwn presence and infection
Classifying Mycoses
Can be be classified by:
Site of infection
- superficial (at stratum/surface of skin)
- cutaneous (into epidermis)
- subcutaneous (into fat layer under skin)
- systemic (SCARY - gets into bloodstream)
Route of acquisition
- exogenous (from environment)
- endogenous (colonized by fungi you already have - fungi in microbiome)
Type of virulence
- primary mycoses (HEALTHY ppl get this)
- opportunistic mycoses (IMMUNOCOMPROMISED ppl get this)
Dermatophytic fungi
- most superficial + cutaneous mycoses are caused by dermatophytes
- most dermatophyte infections are caused by molds (filamentous fungu) of genera Trichophyton, Microsporum and Epidermophyton
- infections are usually self-limiting (no cellular immune response)
- can be treated using topical antifungal drugs or oral drugs if severe
Ex. athlete’s foot, ringworm (NOT a worm)
Opportunistic systemic mycoses
- exploit the imbalance btwn the host and pathogen in immunocompromised ppl
- 2 most common are yeast species in the genus, Candida and molds in the genus Aspergillus
Risk factors for opportunistic systemic mycoses
- HIV infection and AIDS
- solid-organ transplantation
- anticancer chemo (suppresses immune system)
- granulocytopenia (lower # of neutrophils)
- premature birth
- old age
- use of corticosteroids (lowers immune system)
- use of broad-spectrum antibiotics - kills good bacteria too (causes vaginal yeast infections)
- central vascular cathethers (contamination)
- GI surgery
- colonization w/ fungus
Candidiasis
- a few cause invasive infections
- large proportion of humans carry Candida on epithelial surfaces of the mouth, GI tract, vaginal tract and skin
- most frequent infections C. ALBICANS
Some superficial candidiasis infections
- oropharyngeal candidiasis
- denture stomatitis
- chronic mucocutaneous candidiasis
Virulence factors of Candida
- adhesins
- phenotypic switching
- dimorphism (morphology changes to hyphoprojection to become invasive - looks like yeast then filamentous fungi)
- extracellular hydrolases (secrete ENZYMES like proteases + lipases)
Invasive candidiasis
- occurs when cells penetrate through the epithelia + are disseminated systemically throughout the body by blood (candidemia) to infect a bunch of organs
- yeast lands on epidermis + undergoes dimorphism
- yeast invades tissue + creates BIOFILM (evades immune system)
Symptoms: fever and chills (same as viral + bacterial infections - hard to diagnose)
Diagnosis of candidiasis
Superficial candidiasis
- SWABS are taken from affected area and inoculated onto agar plates
- changes colour based on species
Invasive candidiasis
- blood samples can be inoculated into culture medium
- blood culture can fail to detect
Other tests are detection of anti-Candida antibodies and Candida antigens in blood samples
Also can use epidemiology - DNA fingerprinting, microarrays, PCR (NOT done diagnostically - long time)
Aspergillosis
Filamentous fungi
- SAPROPHYTIC fungi (eats waste)
- the one that most frequently causes infection is A. FUMIGATUS
Aspergillus infection
A. fumigatus conidia are dispersed easily in air and routinely INHALED by humans and they penetrate deep into the LOWER RESP TRACT
- conidia is destroyed by alveolar macrophages in immunocompetent
- in immunocompromised ppl, spores settle, germinated, invade and lead to invasive aspergillosis
Virulence factors of Aspergillus
Thermal tolerance
- thrive + grow in extreme temps (NOT dormant stage)
Proteinase production
- degrades proteins
Gliotoxin production
- SUPPRESSES immune system
Environment stress resistance
- resistant to oxidative stress, pH
