fungi and opportunistic infections Flashcards
are fungi eurkaryotic or prokaryotic
eukaryotic
what are the 3 classifications of fungi
unicellular (yeasts)
filamentous (moulds)
dimorphic
explain the features of unicellular fungi
- facultative anaerobes
- reproduce asexually by budding
- produce colonies on agar
explain the features of filamentous fungi
- aerobes
- reproduce by conidia (asexual spores)
- produce mycelia on agar
explain the features of dimorphic fungi
they can switch between unicellular and filamentous forms
what is a hypha
a long, multicellular condidium (asexual spores)
which type of fungi is more virulent to humans and why
dimorphic fungi - because they can grow as filamentous organisms in the environment and then change to growing as unicellular within us
where do dermatophytes live on humans
within keratin layers (hair, skin)
give an example of a dermatophyte
tinea corporis = ring worm (not actually a worm!)
what are the 3 types of candidiasis infection
- mucocutaneous
- chronic mucocutaneous
- systemic (causes septicaemia)
what are 2 diseases caused by cryptococcosis
pulmonary infection
meningitis
what is important to remember about crytococcocal meningitis
it is an AIDS defining illness
what are the two agents that cause cryptococcosis
C. neoformans
C. gattii
what are the 3 types of aspergillosis infection
- saprophytic (fungus ball)
- allergic
- systemic
how do you diagnose fungal infections
microscopy culture antigen detection PCR mass spectrometry
what are the systemic anti-fungal chemotherapy drugs
polyenes (amphotericin B)
triazoles (fluconazole)
echinocandins
5-fluorocytosine
what are the topical anti-fungal treatments
polyenes
imidazoles
what are the targets of anti-fungal medications
ergosterol in cytoplasmic membrane
nucleic acids
which anti-fungal drugs affect the cytoplasmic membrane and how
polyenes affect the integrity
allylamines, trizoles and morpholines affect the synthesis
what is the bad thing about using anti-fungals that target the cytoplsamic membrnae of fungi
they also bind to our cholesterol in our membrane
which antifungal drug affects the nucleic acids of fungi
5-flurocytosine = converted to 5-flurouracil - affects DNA and RNA synthesis
empiric treatment of candida spp
fuconazole (trizaole 1st gen)
empiric treatment of cryptococcus
amphotericin B (polyene) + 5-flurocytosine
empiric treatment of aspergillus
voriconazole (triazole 2nd gen)
empiric treatment of dimorphic fungi
amphotericin B (polyene)
which opportunistic bacteria are associated with nosocomial epidemics
- staph aureus
- Klebsiella pneumoniae
- enterococcus spp
- pseudomonas aeruginosa
- enterobacter spp
- serratia spp
what are the local alterations of a patient that allow infection by opportunistic pathogens
- anatomical defect
- surgical and other wounds
- burns
- catherterisation
- foreign bodiesin general
what are the systemic alterations of a patient that allow infection by opportunistic pathogens
- extremes og age
- leucopenia
- malignancy
- malnutrition
- diabetes
- liver disease
- certain infections (HIV, measles)
- treatment with antimicrobials
- primary immunodeficiency
what are the types of infection that a patient can get with an opportunistic infection
- wound infection
- UTI
- intra-abdominal infection
- pneumonia
- septicaemia
- meningitis
what are the features of pseudomonas
- gram negative rod
- motile
- aerobes or facultative anaerobes
- non-fermenting, non-sporing
- catalase and oxidase positive
- low nutritional requirements
pseudomonas is divided into different species according to…
biochemical tests
how is pseudomonas aeruginosa subtyped
serotyping, biotyping
which 4 bacteria usually colonise the respiratory tract of patients with CF
psuedomonas aueroginosa
burkholderia cepacia
stenotrophomonas maltophilia
burkholderia pseudomallei
which systemic infections is pseudomonas aeruginosa now mostly associated with
penumonia, UTI and sepsis
which superficial infections is pseudomonas aeruginosa associated with
skin - wound infection, otitis externa, folliculitis
eye - keratitis, corneal ulcer
(places where innate immunity is reduced)
how does pseudomonas aeruginosa adhere to skin
via flagella, pili and LPS
- LPS and flagellin bind to TLRs -> affect cytokine production
why is pseudomonas aeruginosa associated with patients with CF
because it binds to the CFTR and it is not inhibited by high salt concentrations
what features of pseudomonas aeruginosa help it to adhere and invade other than flagella and LPS
- once adherent, it tends to produce a biofilm
- it has a capsule - assists adherence and biofilm formation, and makes it resistant to immune system
what are the properties of pseudomonas aeruginosa within the biofilm it makes
- non motile
- more adherent
- more capsule materia
- less invasive
- slow growth
- increased R to AB
- shorter LPS
what causes the change in properties of pseudomonas aeruginosa when it is in a biofilm
activation of genes that are regulated by quorum sensing
what things help pseudomonas aeruginosa spread through the tissues
flagella
exoenzymes
exotoxins
LPS-CFTR mediated nvasion
which exoenzymes does pseudomonas aeruginosa have and what do they do
proteases, haemolysins, phospholipases, elastase –> act on pulmonary tissue and surfactant
what exotoxins does pseudomonas aeruginosa have and what do they do
exotoxin A, exoenzymes S and U –> inhibit phagocytosis
ways to manage pseudomonas aeruginosa in the environment
- reduce risk of susceptible patients
- be on alert for infection and treat early
- practice high levels of hand hygiene
- use contact lenses and solutions appropriately
- lifelong monitoring and Tx of CF patients
