Infection Corrections Flashcards
What is the most common fungal infection? How would you test for this infection?
Aspergillus
PCR for Aspergillus
Or test for cell wall components
Beta glucan
Galactomannan
which endotoxin is commonly seen in the wall of gram negative bacteria?
Lipopolysaccharide
how can microorganism enter a non-phagocytic cell?
zipper method - trick cell into forming cell junction with microorganism
trigger method - bacteria injects things into the cell so the cell moulds around it.
for some viral infections there is no treatment and the host must fend of the infection themselves.
what must occur to initiate an effective host response?
cells form a viral peptide-MHC class 1 complex which is presented on the surface of the cell
how does staphylococcus epidermidis cause infection?
produces an extracellular polysaccharide slime that facilitates adherence to prosthetic material surfaces e.g. catheters or central lines
the slime becomes part of an expanding biofilm which can be difficult to eradicate
which antibiotic is used to treat staph aureus?
beta lactams (e.g. fluclox) or glycopeptides (vancomycin)
both act as cell wall synthesis inhibitors
what allows clostrodium (c.difficile) to survive outside of host for long periods?
form spores
spores are the most resiliant life form known - they can survive boiling, UV light ad bactericidal chemical agents
which antibiotic is used to treat C.difficile?
oral metronidazole (or oral vancomyocin):
* these are used against anaerboic bacteria and protozoa
how does HIV bind to lymphocytes?
gp120 docking glycoprotein binds to CD4 receptors
It is extremely important to avoid alcohol while taking which antibiotics?
metronidazole since it inhibits aldehyde dehydrogenase resulting in accumulation of acetaldehyde
what disease does helicobacter pylori cause?
main cause of gastric and duodenal ulcers + can result in gastric cancer
since it is able to survive a highly acidic environment
what investigation must be completed before antibiotics are aministered for sepsis?
blood culture
how does normal flora prevent the growth of candida albicans in the vagina?
normal flora which is the lactobacillus species produces lactic acid
what is the function of CRP?
promotes opsonin mediated phagocytosis
which nisseria meningitidis virulence factor is part of the vaccine that protects some but not all serogroups of nisseria meningitidis?
capsule - protects against phagocytosis
the capsule varies amongst different serogroups
which antibiotic is used to treat nisseira meningitidis?
ceftriaxone
what kind of swab is used to detect presence of nisseria meningitidis?
throat swab
which immune components are activated in a viral infection?
virus infection stimulates TH1 response which activates CD8 T cells and stimulate their differentiation and expnsion into cytotoxic T lymphocyte
the THC 1 response also regulates the production of antibodies against the virus
what are the T cell dependent and independent antibodies?
T cell independent: IgM
T cell dependent: IgA, IgE, IgG
what does a high IgM to IgG ratio indicate?
acute infection = this is the first time patient has been exposed to pathogen
what does a high IgG to IgM ratio indicate?
chronic infection = patient has been exposed to pathogen before
what is the function of IgG antibodies?
phagocytosis
complement activation
neonatal immunity
toxins/virus neutralisation
what is the function of IgM antibodies?
complement activation
what is the function of IgE antibodies?
immunity against helminths
mast cell degranulation
what is the function of IgA antibodies?
mucosal immunity
which immune componets are affected in DI george syndrome?
T + B cells
since T cells are needed to activate B cells
what is the method of screening MRSA?
nose swab
what is the winter vomitting bug?
norovirus
what is the pattern of infection for the herpes viruses?
latent
which plasmodium species is commonly associated with severe malaria?
plasmodium falciparum
which blood test is most useful in diagnosing malaria?
blood flim
where is CSF produced in the body?
choroid plexus in ventricles
how does the body recognise nisseria meningitidis?
LPS is recognised by toll like receptors on dendritic cells
how do patients with endocarditis commonly present?
fever
roth spots
painful osler nodes
nailbed haemorrhages and emboli
tricuspid valve regurgitation - systolic murmur heard lower left sternal border
Hep B serology
- what does hep B sAg indicate?
- what does hep B eAg indicate?
- indicates presence of virus
- highly infectious
what is the most common oppurtunistic infection in patients with HIV?
pneumocystis jiroveci pneumonia (PJP)
how does plasmodium cause jaundice?
haemolysis
oseltamivir is a neuraminidase inhibitor, what is its method of action?
block emergence of virus from infected cell
what is meant by the term cold adapted vaccine?
virus can grown in the nose and throat but not the lower respiratory tract where temp is higher
what is the function of T cells activated by MHC class II?
- Activate neutrophils through IL17 - this is the only function performed by Th17 (a certain type of T helper cell).
- Increase eosinophil number through IL5 - done by Th2
- Activate B cells through IL4 - done by Th2
- Activate mast cells through IL4 - done by Th2
which cells in the body are CD4+?
naive T cells
what happens in the planktonic phase of biofilm formation?
bacteria enter a spore-like state, and move freely without having to be in a colony
how would the R0 (Basic Reproduction Rate) of an infection be defined?
The number of secondary infections produced by a single case of an infection in a population that is totally susceptible
what are 4 bedside observations seen in patients with suspected sepsis?
high respiratory rate
low BP
low or normal oxygen saturation
high pulse rate
what are the different components of the sepsis 6 bundle? be specific
- oxygen if oxygen saturation <92%
- ensure senior clinician attends
- IV antibiotics
- IV fluid
- monitor urine output, NEWS2 score and repeat lactate
- obtain IV access and take bloods
what are 4 bacteria that commonly cause pneumonia?
- streptococcus pneumoniae
- haemophilius influenza
- staphylococcus aureus
- legionella pneumophilia
