9F: Evolving Pathogens

Question 1

Antimicrobial Agent:

Answer 1

an agent that kills or slows the growth of microorganism

• E.g. Antiseptics, disinfectants, antifungals, antivirals

Question 2

Antimicrobial Resistance:

Answer 2

the ability of a microorganism to survive exposure to an antimicrobial agent

• Can develop either through natural selection or through allele mutations

Question 3

Factors contributing to the formation of antibiotic resistant bacteria:

Answer 3

• Inappropriate compliance with a treatment plan where antibiotics are either prematurely stopped or continued on for too long
  • Inappropriate use of antibiotics, where they are prescribed when not required
  • The widespread use of antibiotics which can increase the probability for an individual prescribed antibiotic to be inhabited by antibiotic resistant bacteria allow for natural selection to take place

Question 4

Bacterial Conjugation:

Answer 4

the process in which bacteria exchange genetic material via direct cell to cell contact

Question 5

The development of Antibiotic-Resistant Bacteria:

Answer 5

1. Variation: in a population of bacteria, there are individuals resistant and susceptible to an antibiotic
   2. Selection Pressure: the exposure to the antibiotic serves as an environmental selection pressure
   3. Selective Advantage: the selective advantage is conferred to bacteria with resistance to the antibiotic
   4. Heritability: Bacteria resistant to the antibiotic are able to replicate and pass on the allele via bacterial conjugation, increasing the allele frequency

Question 6

Mechanisms contributing to the modification of viral surface antigens: Antigenic Drift:

Answer 6

Antigenic Drift: the small and gradual change in the gene encoding for viral surface antigens

- Normally memory cells will be able to recognise basic mutated surface antigens from previous viruses, however after multiple accumulated mutations, a new subtype is created, which is no longer recognized by the memory cells

Question 7

Mechanisms contributing to the modification of viral surface antigens: Antigenic Shift:

Answer 7

Antigenic Shift: the sudden and significant mutation in the gene encoding for viral surface antigens

- Occurs when two or more different strains combine when coinfecting the same host, forming a new subtype through Viral Recombination

- Extremely infectious due to decreased ability to create natural immunity