Antibiotic Resistance + HAIs

Question 1

Explain the concept of an “evolutionary race” 5

Answer 1

• Struggle between human immune system and pathogens to outcompete each other
• As humans evolve better and better immune systems to fight pathogens
• Pathogens evolve better and better ways to evade immune systems of hosts
• Strong selection pressures on both sides cause competition
• Host selection pressure: prevent pathogen infection and pathogen selection pressure: avoid immune system

Question 2

Give the 2 ways that HIV evades the specific immune response

Answer 2

• Antigenic variability

- Reduced HIV detection and recognition

Question 3

Explain antigenic variability and this creates problems for the immune system 6

Answer 3

• Mutation in DNA of HIV’s antigen gene
• Changes tertiary structure of HIV antigen
• Causes antigenic variability - new strains of the virus formed
• Memory T cells no longer recognise new antigen
• No secondary immune response
• Immune system must produce primary immune response for each new strain - slow

Question 4

Explain how reduced HIV detection and recognition occurs 2

Answer 4

• HIV kills T helper cells

- Disrupts antigen presentation in infected cells

Question 5

How does TB evade the immune system? 5

Answer 5

• Phagocytes unable to destroy myobacterium tuberculosis
• Produce substances preventing lyosome fusing with phagocytic vacuole
• Bacteria not destroyed and multiply inside
• Antigen presentation doesn’t occur
• T cells not activated

Question 6

What is a “Hospital Acquired Infection”?

Answer 6

Infections caught while the patient is treated in hospital

Question 7

How are HAIs transmitted? 3

Answer 7

• Not hand washing [staff/visitors]
• Coughs and sneezes
• Equipment e.g beds and surfaces not properly disinfected

Question 8

Why are HAIs more likely in hospitals?

Answer 8

Many patients ill with immunosuppression around other ill people

Question 9

How can hospital acquired infections be prevented? 4

Answer 9

• Hospital staff and visitors encouraged to wash hands
• Equipment and surfaces disinfected
• People with HAIs moved to isolation ward - less likely to transmit infection to other patients
• Clothing cleaned in high temperature laundry

Question 10

How can antibiotic resistance occur with natural selection? 2

Answer 10

• Antibiotics create a strong selection pressure

- Only organisms with a resistant allele survive and reproduce

Question 11

Why is antibiotic resistance more common in hospitals?

Answer 11

More antibiotics are used there so bacteria more likely to develop resistance

Question 12

What can cause antibiotic resistance?(4)

Answer 12

• Overuse of antibiotics [for preventing infections/for minor infections]
• Not using narrow spectrum antibiotics [ones targeting specific bacterium]
• Not finishing full course of antibiotics so infection not fully cleared
• Not rotating use of different antibiotics

Question 13

What are the two ways antibiotic resistance occurs in bacteria?

Answer 13

• Natural selection

- Horizontal gene transmittion

Question 14

Explain horizontal gene transmission 3

Answer 14

• Gene for resistance is passed from one bacterium to the other
• Of a same/different species
• In cell to cell contact [conjugation]