infection session 2-6 Flashcards
Gram staining process
first step- crystal violet solution is added
then iodine. rinsed off. acetone added and washed with water. safranin pink added last. > so gram negative will take this up and appear pink
what is the effect of adding iodine in gram staining?
the peptidoglycan layer of gram positive bacteria will take up the stain
what is the endotoxin of Neisseria meningitidis?
part of the lipopolysaccharide found in the outermembrane
what is the structural difference of gram negative vs gram positive?
gram negative have a lipopolysaccharide wall whereas gram positive DO NOT
+ outermost layer is peptidoglycan
how do monocytes appear??
kinds granular with large blobs in middle like a heart or just one blob BUT different to lymphocyte which has one large well circumscribed blob!
Between which two layers is the CSF found?
between the arachnoid mater and Pia mater
within the subarachnoid space
where is CSF produced?
by the choroid plexus in the ventricles
- specialised layer of epithelial cells with capillaries and loose connective tissue
> plasma filtered from the blood by the epithelial cells to produce CSF
important virulence factor of N. meningitidis? its role?
polysaccharide capsule (prevents phagocytosis) >its chemical composition determines the serogroup
- ACWY- capsule is antigenic and determines the vaccine
- B- capsule doesn’t trigger good response so number of sub capsular antigens are added to the vaccine
indicators of bacterial meningitis?
rash cloudy CSF lumbar puncture low glucose count raised white cell count (neutrophils) normal protein
> meningococcal meningitis
example of glycopeptide antibiotic?
vancomycin
example of macrolide antibiotic?
clarithromycin
Trimethoprim mode of action?
inhibit folic acid synthesis
main target group for gentamicin is?
gram negative bacteria
used against SOME gram positive e.g. Viridans streptococci but have profound activity on gram NEGATIVE
What is opsonisation?
the process of antibody enhanced attachment to the phagocyte
monocytes response to bacteria?
produce cytokines (e.g. IL6) and trigger fever and other responses
Where does MRSA commonly colonise?
nose
what is a strong risk factor for C. diff?
inflammatory bowel disease
hospitalisation too
If antibodies against a virus have high IgM to IgG this indicates?
that the patient has NOT encountered the virus previously (second exposure)
which immune components of the adaptive immune response are activated by the flu virus ?
- Cytotoxic T lymphocytes
- T1 Helper cells (TH1)
- antibodies
why is TH1 response essential in virus infections?
T1 helper cells activate CD8 T cells and stimulate their differentiation and expansion into cytotoxic T lymphocytes
> also regulate the production of antibodies against the virus
first step of host response to viral infections?
viral peptide presented by MHC class 1 molecule
organism usually responsible for bacterial endocarditis on prosthetic heart valves?
and its features
staphylococcus epidermis
- Gram positive
- coagulase negative
> ability to adhere to and colonise the prosthetic material and form a biofilm!!
mechanism of action of Beta lactam ? and example?
cell wall synthesis inhibitor.
Flucloxicillin for staph aureus
mechanism of action of glycopeptide ? and example?
cell wall synthesis inhibitor
Vancomycin for MRSA
HIV binds to lymphocyte via which mechanism?
gp120 docking glycoprotein binds to CD4 receptor
which blood test is most useful in diagnosing malaria?
blood film> blood smeared and look at the RBCs
complication of strep sore throat or bacterial pharyngitis?
peritonsillar abscess (quinsy)
when is IgM usually raised?
in the acute infection
when do IgG antibodies appear?
after few weeks
what does a pattern of high IgG and absent IgM indicate?
past infection
what can cause rupture of the spleen?
EBV
in which cell is EBV maintained for life?
B lymphocyte (latent infection)
cell characteristics of acute EBV?
- large inc in CD8+ T cells
> T cells recognise EBV cells and coordinate immune response
aortic stenosis- which murmur is heard?
an ejection systolic murmur in the 2nd intercostal space on the right
> abnormalities heard when blood is pumped OUT the left ventricle when it contracts in systole.
- classic crescendo-decrescendo systolic murmur
recognition of Neisseria meningitidis is based on?
lipopolysaccharide (LPS) recognised by toll-like receptor (TLR) on dendritic cells
where are Toll-like receptors ?
occur on dendritic cells and macrophages
which is heard on auscultation of the heart when a patient has endocarditis (tricuspid valve most commonly affected)?
systolic murmur in the lower left sternal border
> tricuspid regurgitation (incompetence)
