Session 4 - Hospital Acquired Infections And Adaptive Immunity

Question 1

How can the practice of HCPs effect the likelihood of hospital acquired infections spreading?

Answer 1

• general and specific activities of HCP
• policies and their implementation
• regional + national political initiatives
• organisational structure
• leadership at all levels

Question 2

Name some of the most common viruses which can cause hospital acquired infections.

Answer 2

• Blood Bourne Viruses (HepB/C, HIV)
• Norovirus
• Influenza
• Chickenpox

Question 3

Name some of the bacteria that can cause hospital acquired infections.

Answer 3

• Staph Aureus (including MRSA)
• Clostridium Difficile
• E.coli
• Mycobacterium tuberculosis

Question 4

How can patient-patient transmission be stopped in a health care environment?

Answer 4

• protect susceptible patients

- isolate infected patients

Question 5

What environmental interventions can be made to a healthcare environment to reduce the risk of hospital acquired infections?

Answer 5

• Good cleaning practices
• Medical devices - single use, sterilisation
• Good food hygiene practices
• +ve/-ve pressure rooms
• Building environment - enough space between beds, toilets, wash hand basins

Question 6

How does Clostridium Difficile usually cause infection?

Answer 6

• usually part of normal flora in small bowel
• causes infection when antibiotics are used against other bacteria
• less competition for C.Diff’s growth
• grows so much it becomes pathogenic

Question 7

What symptoms would a patient infected with Clostridium Difficile present with?

Answer 7

• persistent diarrhoea
• bloody diarrhoea
• weight loss
• high temperature

Question 8

What is the treatment for infection with Clostridium Difficile?

Answer 8

• Stop taking other antibiotics if possible
• Oral Vancomycin. For 10-14 days
• May require surgery to remove part of diseased bowel

Question 9

How is staphylococcus aureus usually spread and how can it then cause infection?

Answer 9

• Skin->Skin contact with infected individuals
• if it then penetrates the skin it can then cause infection
• can cause blood poisoning or endocarditis

Question 10

What are the four main antigen-presenting cells?

Answer 10

• Dendritic Cells
• Langerhan’s cells
• Macrophages
• B cells

Question 11

What does MHC stand for and why are these molecules important?

Answer 11

Major Histcompatibility Complex

These are a set of cell surfaces proteins essential for the acquired immune system to recognise foreign molecules

Question 12

What is the importance of Co-dominant expression in MHC molecules?

Answer 12

Both of the parental genes are expressed meaning that there are a much greater variety of MHC molecules made.

Question 13

What is the main functional difference between Class I and Class II MHC molecules?

Answer 13

Class I present peptides from Intracellular microbes

Class II present peptides from Extracellular microbes

Question 14

Which T-cells do each of the Classes present to?

Answer 14

I -> CD8+ T-cells

II -> CD4+ T-cells

Question 15

How does recognition by the CD4+ T-cells cause an immune response?

Answer 15

• Stimulation of antibody production by B-cells
• Complement pathway activation
• Activation of neutrophils. Eosinophils + Mast Cells

Question 16

Why is it important to consider MHC molecules when completing an organ transplant?

Answer 16

• MHC molecules are the major reason for organ transplant rejection
• If the MHC molecules mismatch between donor and recipient then there will be rejection

Question 17

How does CD8+ T-cell recognition of Intracellular MHC molecules cause an immune response?

Answer 17

Cytotoxic T-cells are activated which kill all infected cells with that particular MHC molcule.

Question 18

The release of which substance allows CD8 cytotoxic T-cells to cause lysis of infected cells?

Answer 18

Perforin

Question 19

What cells do B-cells divide into when activated?

Answer 19

Plasma Cells + Memory Cells