Midterm 2 Flashcards
Approximately how many fungal pathogens of humans are there
~300
Mycosis (pl. mycoses
fungal infection of animals
Superficial classification
infection of hair or skin epidermis
Cutaneous classification
infection of skin, nails and mucosal surfaces
Subcutaneous classification
subcutaneous tissues, muscle
-typically initiated by piercing to the skin
Systemic classification
deep seated infection which affects organs
endogenous pathogens
come from the microbiome of host and become pathogenic due to a compromised immune system
(ex. Candida species)
Exogenous pathogens
acquired from the environment via inhalation or penetrating injury
(ex. Aspergillus moulds)
Primary pathogens
can establish infection in healthy host
(ex. dimorphic fungal pathogens)
Opportunistic pathogens
can cause disease in individuals within immunocompromised
(Cryptococcus)
-highest mortality rates
Why have infections due to opportunistic pathogens been on the rise
-can easier find them
-antibiotic resistance
-have adapted to climate change and can better invade the human body
Most common opportunistic fungal pathogens of humans
-Aspergillus
-Candida
-Cryptococcus
tineas
superficial cosmetic fungal infections on the outer skin or hair
-no tissue is invaded
-typically innocuous
Examples of superficial fungal infections
Malassezia species
-Tinea versicolor
What does Malassezia use to break down oils on the scalp
lipase and phospholipases
Where do dermatophytes grow
in skin, hair, or nails
-where the protein keratin is deposited
What type of fungi are dermatophytes
all filamentous ascomycota
What symptoms do dermatophytes cause
irritation and inflammation of underlying epithelial cells
What fungal diseases can dermatophyte species cause
common ‘tinea’ diseases like ringworm and athlete’s foot
What do dermatophytes secrete
proteinases, elastases, and keratinases that break down skin
What can cutaneous infections cause
superficial mucosal infections of the mouth and vaginal yeast infections
What are subcutaneous mycoses caused by
fungi that are normally saprotrophic inhabitants of soil
symptoms of subcutaneous fungal infections
chronic localized infections of the skin and subcutaneous tissue and chronic inflammation and ulceration
What is one of the most common pathogens of subcutaneous fungal infections
Sporothrix schenckii
Are subcutaneous fungi thermally dimorphic
yes
-filamentous fungus in soil/environment, yeast in human host
Describe primary systemic pathogens
rare and can affect healthy people
-often acquired by inhalation of spores from soil and usually begins as a lung infection
Name 3 important dimorphic fungi pathogens
-Blastomyces dermatitidis
-Coccidiodes immitis
-Histoplasma capsulatum
All part of Ascomycota
What do Histoplama capsulatum form
forms microconidia and macroconidia
What can people develop from Histoplasma capsulatum
histoplasmosis through inhalation of spores
Where is Histoplasma capsulatum found
river valleys and in central/eastern USA, also associated with animal droppings
Where is Blastomyces dermatitidis found
mould lives in soil and decaying wood, in northern Ontario and Manitoba
What can people develop from Blastomyces dermatitidis
blastomycosis though inhalation of spores
Where is Coccidioides immitis
lives in dust and soil in southwestern US
What are Coccidiodes immitis outbreaks linked with
changing climate factors
What can people develop from Coccidioides immitis
coccidioidomycosis (valley fever)
What spores to Coccidioides immitis form
arthroconidia
What do Coccidiodes form during host-associated growth
spherules
What do spherules do
When it enters the body it expands in size and undergoes cellular division
When it ruptures it releases endospores which can form new spherules
Emergomyces
newly emerging group of dimorphic fungal pathogens with global distribution
Primarily affect immunosuppressed patients
How do dimorphic fungi sense temperature
using histidine kinase signaling cascades
What are histidine kinase signaling pathways
well conserved sensory signaling regulators
What are histidine kinase signaling cascades made up of
a variable N-terminal sensor domain and a conserved C-terminal transmitter domain
What does the histidine kinase (HK) act as
acts as the environmental sensor of temp change and involves 4 phosphorylation events
What are the 4 phosphorylation events after HK gets an environmental cue
- The HK is auto phosphorylated
- Intramolecularly HK phosphorylation
- Phosphorylation of transferase protein
- Phosphorylation of response regulator protein
What does the MAPK cascade ultimately lead to
activation of transcription factors and transcriptional regulation
What does iprodione do in dimorphic fungi
inhibits HK so inhibits yeast growth transtiion
What are dimorphic spores ingested by when the are inhaled
alveolar macrophages
When do dimorphic fungi undergo extensive transcriptional re-wiring
during morphogenesis from mould to yeast
Name a big cell wall change during morphogenesis
there is a reorganization of glucan
beta-glucan declines from~40% in hyphae to ~5% in yeasts
What does the change in glucan content in cell wall help with
helps limit immune cell recognition by Dectin-1
Adhesins
help yeast adhere to host cell tissues
Secreted factors
induce host macrophage apoptosis and lysis
What genus is the most common cause of fungal diseases
Candida species
Are Candida ascomycota or basidiomycota
Ascomycota yeasts
What is the clade called that most Candida species are in
CTG clade
What species is the most common cause of candida infections
Candida albicans
Are Candida albicans dimorphic or polymorphic
polymorphic yeast
Are Candida albicans infection\s exogenous or endogenous
endogenous
- no known environmental reservoir
How do mucosal Candida infections occur
result of fungal overgrowth from people taking antibiotics or immunosuppressants
Describe Candida oral thrush
infection of the mucous membranes of the mouth
-occurs when immune system is compromised
What is a vaginal yeast infections
Candida infection of the vaginal mucous membranes
What host factors could lead to vaginal yeast infections
-antibiotics (kills bacteria and yeast take over)
-hormonal changes
-pregnancy
-diabetes
Describe invasive Candida infections
endogenous fungi penetrate through epithelial cells
-Candida enters bloodstream
What combination of factors lead to invasive Candida infections
-overgrowth
-breach of mucosa/epithelium
-compromised immune response
Name 3 important immune cells that target Candida
- macrophages
- T helper cells
- neutrophils
What are the general host risk factors for invasive Candida
-disturbed bacterial community
-immunosuppression
-access to bloodstream
Biofilms
yeast and hyphal cells, adhering to a surface, enclosed in an extracellular matrix
Where does C. albicans form robust biofilms
medical devices
-catheters, valves
How are biofilms removed
they are highly resistant to antifungals so typically must be physically removed
what are the mortality rates of invasive Candida albicans
~50-80%