Lecture 1: Acute & Chronic Infections

Question 1

What role do N-formylated peptides have in Neutrophil Signalling?

Answer 1

They play a major role as potent chemoattractants

Question 2

What are N-formylated peptides recognised by?

Answer 2

Recognised by the macrophage

Question 3

Where do N-formylated peptides originate from?

Answer 3

Degraded bacterial proteins

Question 4

What changes occur in macrophages to allow for engulfing?

Answer 4

Changes in actin filaments

Question 5

How do antigen presenting cells act?

Answer 5

Presenting antigenic determinants to T cells via MHC II proteins

(communication between T-helper and macrophage)

Question 6

How do antigen presenting cells become effective ‘killers’?

Answer 6

They become up-regulated

Question 7

What is involved in the acute response to infection?

Answer 7

Hypothalamus - fever, re-setting body temperature
Brain - somnulence

Vascular permeability changes - hypotension & shock
(tight junctions between blood capillaries opening up)

Mobilisation of WBC - neutrophilia
(from the bone marrow)

Enhancement of neutrophil killing mechanism

Release of acute phase proteins from liver

Question 8

What are the characteristics of the chronic response to infection?

Answer 8

Muscle and fat mobilisation - weight loss
(chronic bacterial infections are a catabolic process)

Fibroblasts stimulated - healing and repair

(continued release of acute phase proteins)

Question 9

What are the components of acute phase proteins and what is the role of each?

Answer 9

C-reactive protein, mannose binding lectin and fibrinogen

Mannose binding lectin: binds non-specifically to the surface of bacteria - aids phagocytic process

C-reactive protein: marker of the response to infection

Fibrinogen: increases erythrocyte sedimentation rate

Question 10

What is the cause of the increased erythrocyte sedimentation rate in the acute response to infection?

Answer 10

Fibrinogen binds to red blood cells and causes them to sediment faster

Question 11

What are the differences between the 3 complement activation pathways?

Answer 11

Classical pathway: antigen-antibody complexes (pathogen surfaces)

MB-lectin pathway: mannose-binding lectin binds mannose on pathogen surfaces

Alternative pathway: pathogen surfaces

Question 12

What marker drives a pathogen for phagocytosis?

Answer 12

C3b

Question 13

What do C3a and C5a do in the complement activation pathway?

Answer 13

Peptide mediators of inflammation

Phagocyte recruitment

Question 14

What does C3b do in the complement activation pathway?

Answer 14

Binds to complement receptors on phagocytes

Opsonization of pathogens

Removal of immune complexes

Question 15

What do the terminal complement components do?

Answer 15

Membrane-attack complex

Lysis of certain pathogen and cells

Question 16

What do Mannose binding lectin binding sites recognise?

Answer 16

D-mannose
L-fucose
N-acetylglucosamine

Question 17

What does Mannose binding lectin bind with?

Answer 17

MBL binds with high affinity to mannose and fucose residues with correct spacing

Question 18

How much do C-reactive protein levels increase within hours of inflammation? And what it the increase induced by?

Answer 18

Increase up to 10,000 fold

Indue by infection or injury

Question 19

What are the rough baseline levels of C-reactive protein naturally circulating?

Answer 19

Low levels

Question 20

What is bacteraemia?

Answer 20

The presence of bacteria in the blood

Question 21

What are the 3 types of bacteraemia?

Answer 21

Transient: lasts less than 20 mins

Intermittent: implying an extravascular source

Continuous: implying intravascular source (growing within circulatory system)

Question 22

What is the normal range of bacteria in a bacteraemic patient?

Answer 22

20-50/ mL

Question 23

How are blood cultures taken?

Answer 23

1. Inform patient of procedure
2. Apply tourniquet and select vein for puncture
3. Wash hands using alcohol hand rub and clean puncture site with alcohol wipe
4. Enter being within palpating site again

Question 24

What are the different types of growth media for blood cultures?

Answer 24

Blood in 5% CO2
Blood agar anaerobic
Chocolate agar in 5% CO2
Enteric agar for coliforms
Sensitivity agar (antimicrobial sensitivity)

Question 25

What is the process of gaining a positive blood culture sample?

Answer 25

Sample is inoculated into bottle and incubated. Signal received of a positive test (changes in pH, CO2 production, absorbance) Sample removed from positive bottle Sample gram stained

Question 26

What would be an indication of a gram-positive cocci?

Answer 26

Dark blue/ violet in colour

Question 27

What type of bacteria is gram positive?

Answer 27

Streptococcal

Question 28

What type of bacteria is gram negative?

Answer 28

Meningococcus

Question 29

What would be an indication of a gram-negative bacteria?

Answer 29

Pink in colour

Question 30

What is bacterial endocarditis?

Answer 30

Physical damage to the value endothelium

Question 31

What is bacterial endocarditis caused by?

Answer 31

Occurs by blood turbulence or the impact of micro-particles

Question 32

What is deposited in the blood as a result of bacterial endocarditis? What can occur as a result of the deposits?

Answer 32

Fibrin and platelets Bacteria passing by in the blood can attach to and colonise the deposits

Question 33

What do bacteria in a valve give rise to?

Answer 33

Local pathology (local tissue damage) Distant pathology due to septic emboli Immune response (continued bacteraemia) Untreated can cause death

Question 34

What is prosthetic valve endocarditis?

Answer 34

Bacteria can be introduced at the time of operation The infection may manifest weeks or months after the opeation

Question 35

What can prosthetic valve endocarditis be divided into?

Answer 35

Early: < 1 year Late: > 1 year

Question 36

What is the process of blood culturing for endocarditis?

Answer 36

3-4 blood sets are collected from different sites

Question 37

How is a positive test identified with continuous bacteraemia?

Answer 37

When 7/8 bottles are positive within 2 days Antibiotic sensitivity tests are then conducted

Question 38

What antibiotics are commonly used in endocarditis?

Answer 38

Bacteria commonly sensitive to penicillin Benzylpenicillin (4-hourly) AND Gentamicin (2-4 weeks) Vancomycin and teicoplanin (glycopeptides): streptococcal and staphylococcal endocarditis (penicillin allergy)

Question 39

What ae the signs bacterial endocarditis is being overcome?

Answer 39

Patient's temperature returns to normal Return of C-reactive protein and erythrocyte sedimentation rate