Infection

Question 1

Give examples of gram positive bacteria

Answer 1

Staphylococcus aureus Streptococcal pneumoniae Clostridium difficle

Question 2

Give examples of gram negative bacteria

Answer 2

Neisseria meningitides Escherichia coli Pseudmonas aeruginosa

Question 3

Give examples of encapsulated bacteria

Answer 3

Staphylococcus aureus Streptococci pneumoniae Neisseria miningitides Pseudomonas aeruginosa

Question 4

Define SIRS

Answer 4

Systemic inflammatory response syndrome. 2 or more of the following:

• Temp: 38^oC
• HR: >90bpm
• RR: >20/min
• WBC: <4 or >12 x 10⁹/L

Question 5

Define sepsis

Answer 5

SIRS + suspect pathogen

Question 6

Define severe sepsis and septic shock

Answer 6

Severe sepsis: SIRS and organ dysfunction/hypoperfusion
Septic shock: Severe sepsis but unresponsive hypotension depsite IV fluid administration

Question 7

What are the sepsis six?

Answer 7

O₂ = give oxygen

F = give fluid

L = lactate level

U = urine output

I = infection cultures

D = drugs (antibiotics)

Question 8

What type of virus is HIV?

Answer 8

Enveloped positive single strand RNA

Question 9

Describe how HIV infects host cells

Answer 9

• HIV virus attaches to CD4 receptor
• Viral RNA is inserted into host DNA to ensure replication
• HIV causes tissue destruction from either the virus or host’s response to virus-infected cells
• Gives immunological state

Question 10

What type of virus is influenza?

Answer 10

Enveloped negative single strand RNA

Question 11

Explain what is meant by antigenic drift

Answer 11

Minor antigenic changes in H and N proteins on outer surface, occurs every year.

Random mutations does not involve change in viral subtype

Question 12

Explain what is meant by antigenic shift

Answer 12

Dramatic changes in antigenic properties of H and N proteins.

From H1N1 to H3N2

Question 13

What are the treatments for influenza?

Answer 13

Neuraminidase inhibitor - prevents release from cell membrane once replicated (e.g. oseltamivir)

M2 ion channel inhibitor - prevents acidification of endosome required for disassembly of virus for replication (e.g. amantadine)

Question 14

What type of virus is hepatitis B?

Answer 14

Enveloped double stranded DNA virus

Question 15

Give some mechanisms of infection

Answer 15

• Haematogenous
• Contiguous (direct) spread
• Inoculation
• Ingestion
• Inhalation
• Vector (e.g. mosquito)
• Vertical transmission

Question 16

Generally how to infections cause damage?

Answer 16

Either through toxin production or interacting with host defences (e.g. inflammation)

Question 17

How does the hepatitis B virus cause damage?

Answer 17

Infected hepatocytes causing cell-mediated response resulting in inflammation and necrosis

Question 18

What type of virus is varicella-zoster?

Answer 18

Enveloped double stranded DNA virus

Question 19

What are the most common pathogenic causes of malaria?

Answer 19

Plasmodium vivax (80%)

Plasmodium falciparum (15%) - more dangerous

Question 20

Describe transmission of malaria

Answer 20

Female anopheles mosquite (vector)

Infected blood products

Question 21

What is the pathogenesis of malaria? And give common signs/symptoms

Answer 21

• Multiply in RBCs
• Cause haemolysis and cytokine release

Anaemia, jaundice, hepatosplenomegaly

Question 22

Give common pathogenic causes of meningitis

Answer 22

Neisseria meningitides

Streptococcus pneumoniae

Question 23

How does neisseria meningitides cause a non-blanching rash?

Answer 23

Toxin release causes destruction of blood vessel wall leading to blood release under the skin

Question 24

Give common causes of typical pneumonia

Answer 24

Streptococcal pneumoniae

Haemophilus influenza

Question 25

Give causes of atypical pneumonia

Answer 25

Chlamydia pneumoniae Mycoplasma pneumoniae Influenza virus Pneumocystis jiroveci (immunocompromised)

Question 26

What does staphylococcus aureus secrete that aid in its survival?

Answer 26

Catalase - catalyses conversion of peroxide to water and oxygen, prevents damage from neutrophils, oxidative burst Coagulase - localised clotting, restricts access of polymorphonuclear neutrophils

Question 27

What are the common causes of hospital-acquired pneumonia?

Answer 27

Escherichia coli Staphylococcus aureus

Question 28

What type of bacteria is helicobacter pylori?

Answer 28

Gram negative bacilli

Question 29

How does H. pylori ensure it's survival?

Answer 29

Burrows into mucus 'un-stirred' later - more alkali Produces urease to convert urea to carbon dioxide and ammonia - neutralises stomach acid Ammonia toxic to epithelial cells so causes inflammation

Question 30

What are the common pathogenic causes of UTI?

Answer 30

Escherichia coli Staphylococcus saprophyticus Staphylococcus aureus - catheter

Question 31

What are the cells of innate immunity?

Answer 31

* Monocytes/macrophages * Neutrophils * Dendritic cells * Natural killer cells * Degranulating cells (mast cells, eosinophils, basophils)

Question 32

What is chronic granulomatous disease?

Answer 32

Mutation on X chromosome causing defective enzymes involved with respiratory burst Neutrophils are attracted to site of infection and phagocytose but are unable to kill pathogens

Question 33

Explain how phagocytes recognise microbes

Answer 33

Micrboes express pathogen-associated molecular patterns (PAMPs) which are recognised by phagocytes expressing pattern recognition receptors (PPRs)

Question 34

Describe the 2 types of PRRs

Answer 34

Collectin - interact with innate immune system Toll-like receptors

Question 35

What are the molecules are opsonins?

Answer 35

Antibodies - IgG, IgM Complement - C3b, C4b Mannose-binding lectin C-reactive protein

Question 36

What are the 3 types of cytokines that macrophages release?

Answer 36

1. Cytokines acting over distance - G-CSF, increases bone marrow production of neutrophils 2. Cytokines acting locally - TNF, increases stickness of endothelial blood cells, more like neutrophils will enter surrounding tissue 3. Chemokines - IL-8, attract other cells (neutrophils)

Question 37

Explain acute phase response

Answer 37

If infection not cleared then macrophages produce more cytokines (IL-1, IL-6, TNF) which surge into circulation and affect other organs * Liver - increases production of serum acute-phase proteins * Hypothalamus - increases body temperature (inhibits replication of viruses) * Nervous system - shivering and sweating

Question 38

How does complement damage pathogens?

Answer 38

1. Membrane attack complex - forms a polymers that binds to pathogen wall and punches holes in it 2. C3a increases vascular permability 3. Increases opsonisation

Question 39

What condition results from a mutation in complement cascade? (Hint: C1 inhibitor gene mutation)

Answer 39

Herediatory angio-oedema

Question 40

Which MHC class, CD type receptors and T cells are specific for intracellular microbes?

Answer 40

MHC I, CD8 T cells causing cytotoxic T cell response

Question 41

Which MHC class, CD type receptors and T cells are specific for extracellular microbes?

Answer 41

MHC II, CD4 T cells and activates T helper cells

Question 42

What is graft-vs-host reaction

Answer 42

Immune cells of the transplanted tissue recognise the recipitent as foreign, therefore mount immune response

Question 43

What are the 4 P's of infection prevention?

Answer 43

1. Patient 2. Pathogen 3. Practice 4. Place

Question 44

What is the difference between primary immunodeficiencies and secondary immunodeficiencies?

Answer 44

Primary immunodeficiencies are a result of a intrinsic defect (congenital) - usually B cell deficiencies Secondary immunodeficiencies are caused by an underlying disease or condition affecting immune compoenets (decreased production or increased loss/catabolism)

Question 45

Give one example of each primary immunodeficiencies: 1. B cell deficiency 2. Phagocyte deficiency 3. T deficiency 4. Complement deficiency

Answer 45

* B cell deficiency - IgA deficiency (B cell unable to switch to IgA) * Phagocyte deficiency - Chronic granulomatous disease * T deficiency - Di George syndrome (incomplete development of thymus) * Complement deficiency - Herediatary angio-oedema

Question 46

Which interleukin is pyrogenic?

Answer 46

Interleukin-1