lecture 14) human fungal pathogens Flashcards
in what type of people are fungal infections most dangerous?
immunocompromised
what type of organisms are fungi?
eukaryotic
where and how is DNA in fungal cells stored?
DNA in chromosomes in nucleus
why are fungal infections harder to treat than bacterial and viral infections?
treatments for infections involve targeting essential processes of the cell to deem them unharmful
as fungal cells are eukaryoties, their essential processes would be the same as ours
how do fungi feed?
absorb nutrients by breaking down organic material into simple molecules using hydrolytic enzymes
what type of fungi are moulds?
filamentous
how quick can filamentous spores grow?
3 days (v quick)
name 3 types of fungi
moulds
yeasts
dimorphic
describe the cell composition of yeasts
mainly unicellular
do all yeasts bud?
no
what is a dimorphic fungi?
fungi that switches between 2 forms in response to changes in the environment
what is a key virulence factor of dimorphic fungi?
their ability to switch morphology
what are the 3 types of diseases that fungi can cause?
superficial mycoses (skin, hair, nails, mucous membranes) subcutaneous mycoses (through wound) deep seated/systemic mycoses (single deep organ or disseminated)
what sort of diseases are subcunateous fungal diseases?
rare tropical diseases
what is a primary pathogen?
directly cause disease
what is an opportunistic pathogen?
in normal situations the pathogen wont cause disease but in certain situations they will
what are the infection of dermatophytes like?
superficial infection of skin, hair or nails
what are the 3 genera that cause dermtophyte infections?
microsporum sp.
epidermophyton sp.
trichophyton sp.
what is the morphology of dermatophytes?
filamentous
where do dermatophytes come from?
soil, animals, people
what do dermatophytes produce?
keratinase
digest keratin as growth substance
infect keratin rich tissues
name the 3 groups dermatophytes are divided into based on habitat
anthropophillic
zoophillic
geophillic
what are anthropophillic dermatophytes?
reservoir and host is man
what are zoophillic dermatophytes?
reservoir is animales, can infect man
what are geophillic dermatophytes?
found in soil
occasionally pathogenic
what group of dermatophytes give the most serious infection?
zoophillic
not used to seeing them in the human body therefore a more enhanced inflammatory response is induced
what type of classification is used for dermatophytes?
non-mycological
aka non-phylogenetic
candida is a normal commensal organism. what does this mean?
commensal means that both parties benefit in cohabitation meaning the human body and candida both benefit when in each others presence
where is candida present in the body?
50% in mouth and GI tract
20% women in genital tract
are all candidas related?
cannot assume that the name candida means they are phylogenetically related
what are the sires of superficial infection of candida?
mouth, vagina, penis, skin, nails
name 3 predisposing factors of candida infections
antibiotics
diabetes (candida thrive in sugary environments)
pregnant women (hormone imbalances)
who are at risk to candida infections?
normal individuals as it is a commensal organism that already lives within us
doesnt take much to tip it to be pathogenic
what could reoccurring vaginal thrush caused by candida be due to?
immune responses that cause symptoms of thrush
how do subcutaneous mycoses cause infection?
inhabitants of soil and vegetation
introduced into the body via puncture wounds
how quickly do subcutaneous mycoses infections take to develop?
months to years
why are they hard to treat?
where they occur is normally in developing countries that have limited facilities
why are subcutaneous mycoses infections not very responsive to treatment?
regular antifungal treatment made for more common infections in the western, more developed world which are used to treat different infections eg thrust
what type of pathogens do invasive mycoses cause infections and which ones kill you?
primary pathogens cuase disease but can be mild
opportunistic pathogens kill people
why dont we hear about invasive mycoses infections?
mainly found in developing countries that may not have the infrastructure to report the cases
what is the impact of better medical intervention on fungal infections?
better medical intervention means more people who are immunocompromised meaning more people being susceptible to fungal diseases
where are invasive mycoses found in the world?
geographically limited
none in the UK
common in endemic regions
what does thermally dimorphic mean?
found in environment in soil etc
what type of disease do invasive mycoses cause?
asymptomatic (no symptoms)
generally mild infections
if there are symptoms it will be a respiratory infection
more serious infections are seen in immunocompromised patients
what sites in the bodt do deep-seated disseminated infections occur?
single organ or widespread (disseminated)
what are the predisposing factors of deep-seated candida infections?
seriously immunocompromised hosts eg neutropenic, organ and bone marrow transplant, cancer
what routes of infection does deep-seated candida infections have?
burns patients
abdominal surgery
catheter
what type of diseases does candida auris cause?
superficial and systemic diseases
what are the key concerns of candida auris?
multi-drug resistance
misdiagnosis
hospital outbreaks
do most species of aspergillosis cause disease?
most of them dont cause disease
only 2-3 species do
what are the routes of infection of aspergillosis?
inhalation of spores
how do we get infections of aspergillosis?
ubiquitous fungus
what is the route of infection for cryptococcosis?
inhalation
sexual cycle produces small spores
although cryptococcosis is dimorphic, how does it grow in patients?
grows as capsulate yeast in patients
where is cryptococcosis found?
pigeon droppings
soil
avian habitats
what diseases does cryptococcosis cause?
pulmonary cryptococcosis (often no symptoms, chronic, lies dormant, see relapses) meningitis in immunocompromised (once in blood it can target the brain)
what disease does pneumocystis cause and what are its symptoms?
pneumocystis pneumonia (dry cough, shortness of breath)
respiratory infection in immunocompromised patients
route of infection is inhalation
why might pneumocystis be non-culturable in vitro?
lacks most of the genes needed for amino acid synthesis
how come pneumocystis was originally classed as a protozoan?
life cycle of a proteozoan but when sequencing the genome it is a fungus
why should we be thankful for pneumocystis?
led us to the first ever report of AIDs
