infection session 2-6

Question 1

Gram staining process

Answer 1

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

Question 2

what is the effect of adding iodine in gram staining?

Answer 2

the peptidoglycan layer of gram positive bacteria will take up the stain

Question 3

what is the endotoxin of Neisseria meningitidis?

Answer 3

part of the lipopolysaccharide found in the outermembrane

Question 4

what is the structural difference of gram negative vs gram positive?

Answer 4

gram negative have a lipopolysaccharide wall whereas gram positive DO NOT

+ outermost layer is peptidoglycan

Question 5

how do monocytes appear??

Answer 5

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!

Question 6

Between which two layers is the CSF found?

Answer 6

between the arachnoid mater and Pia mater

within the subarachnoid space

Question 7

where is CSF produced?

Answer 7

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

Question 8

important virulence factor of N. meningitidis? its role?

Answer 8

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

Question 9

indicators of bacterial meningitis?

Answer 9

rash
cloudy CSF lumbar puncture
low glucose count
raised white cell count (neutrophils)
normal protein

> meningococcal meningitis

Question 10

example of glycopeptide antibiotic?

Answer 10

vancomycin

Question 11

example of macrolide antibiotic?

Answer 11

clarithromycin

Question 12

Trimethoprim mode of action?

Answer 12

inhibit folic acid synthesis

Question 13

main target group for gentamicin is?

Answer 13

gram negative bacteria

used against SOME gram positive e.g. Viridans streptococci but have profound activity on gram NEGATIVE

Question 14

What is opsonisation?

Answer 14

the process of antibody enhanced attachment to the phagocyte

Question 15

monocytes response to bacteria?

Answer 15

produce cytokines (e.g. IL6) and trigger fever and other responses

Question 16

Where does MRSA commonly colonise?

Answer 16

nose

Question 17

what is a strong risk factor for C. diff?

Answer 17

inflammatory bowel disease

hospitalisation too

Question 18

If antibodies against a virus have high IgM to IgG this indicates?

Answer 18

that the patient has NOT encountered the virus previously (second exposure)

Question 19

which immune components of the adaptive immune response are activated by the flu virus ?

Answer 19

• Cytotoxic T lymphocytes
• T1 Helper cells (TH1)
• antibodies

Question 20

why is TH1 response essential in virus infections?

Answer 20

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

Question 21

first step of host response to viral infections?

Answer 21

viral peptide presented by MHC class 1 molecule

Question 22

organism usually responsible for bacterial endocarditis on prosthetic heart valves?

and its features

Answer 22

staphylococcus epidermis

• Gram positive
• coagulase negative
  > ability to adhere to and colonise the prosthetic material and form a biofilm!!

Question 23

mechanism of action of Beta lactam ? and example?

Answer 23

cell wall synthesis inhibitor.

Flucloxicillin for staph aureus

Question 24

mechanism of action of glycopeptide ? and example?

Answer 24

cell wall synthesis inhibitor

Vancomycin for MRSA

Question 25

HIV binds to lymphocyte via which mechanism?

Answer 25

gp120 docking glycoprotein binds to CD4 receptor

Question 26

which blood test is most useful in diagnosing malaria?

Answer 26

blood film> blood smeared and look at the RBCs

Question 27

complication of strep sore throat or bacterial pharyngitis?

Answer 27

peritonsillar abscess (quinsy)

Question 28

when is IgM usually raised?

Answer 28

in the acute infection

Question 29

when do IgG antibodies appear?

Answer 29

after few weeks

Question 30

what does a pattern of high IgG and absent IgM indicate?

Answer 30

past infection

Question 31

what can cause rupture of the spleen?

Answer 31

EBV

Question 32

in which cell is EBV maintained for life?

Answer 32

B lymphocyte (latent infection)

Question 33

cell characteristics of acute EBV?

Answer 33

• large inc in CD8+ T cells

> T cells recognise EBV cells and coordinate immune response

Question 34

aortic stenosis- which murmur is heard?

Answer 34

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

Question 35

recognition of Neisseria meningitidis is based on?

Answer 35

lipopolysaccharide (LPS) recognised by toll-like receptor (TLR) on dendritic cells

Question 36

where are Toll-like receptors ?

Answer 36

occur on dendritic cells and macrophages

Question 37

which is heard on auscultation of the heart when a patient has endocarditis (tricuspid valve most commonly affected)?

Answer 37

systolic murmur in the lower left sternal border

> tricuspid regurgitation (incompetence)