Evolving Pathogens

Question 1

Antimicrobial agent

Answer 1

An agent that kills or slows the growth of microorganisms.

Question 2

Antimicrobial resistance

Answer 2

The ability of an organism to survive exposure to an agent

Question 3

Selective advantage in bacteria

Answer 3

Due to natural variation in bacteria, and as a result of previous, random mutations, some bacteria will be more resistant to an antibiotic than others

Question 4

What is the selection pressure for bacteria?

Answer 4

Presence of antibiotics

Question 5

Bacterial conjugation

Answer 5

The process in which bacteria exchange genetic material via direct cell-to-cell contact, spreading alleles for antibiotic resistance

Question 6

Steps of antibiotic resistance

Answer 6

1. Variation - the population of bacteria has genes resistant to antimicrobials and susceptible
2. Selection pressure - the exposure to an antibiotic is the selection pressure
3. Selective advantage - a selective advantage is to bacteria resistant to the antimicrobial
4. Heritability - Bactera with the selective advantage are able to pass on their alleles via bacterial conjugation to increase allele frequency

Question 7

How can bacteria develop resistance to antibiotics?

Answer 7

Through mutations, bacteria can combat the action of antibiotics

Question 8

Mechanisms for antibiotic resistance in bacteria

Answer 8

-impermeability to antibiotics
-changing the shape of the protein that the antibiotic targets

Question 9

Factors that contribute to the formation of antibiotic resistant bacteria

Answer 9

1. Non compliance when taking antibiotics - patients do not finish their antibiotics, allowing some pathogenic bacteria to survive and reproduce, increasing chance of mutations leading to resistance
2. Inappropriate use of antibiotics - prescribed unnecessarily for viral infections hich may select for antibiotic resistance in normal flora
3. Widespread use of antibiotics - increased use of antibiotics leads to increased natural selection for bacteria that are resistant

Question 10

What happens when the surface antigens of viruses change

Answer 10

-allows them to avoid detection by immunological memory cells developed from past infection
-be unaffected by existing medications

Question 11

Two mechanisms that cause the modification of viral surface antigens:

Answer 11

Antigenic shift and drift

Question 12

Antigenic shift

Answer 12

Sudden and significant mutations in the genes encoding for viral surface antigens. Often occurs when multiple diff strains of a virus combine when coinfecting the same host to form a completely new subtype - through viral recombination (may result in epidemic or pandemic)

Question 13

Antigenic drift

Answer 13

Small and gradual mutations in the genes encoding for viral surface antigens. These cause a new subtype of virus as mutations collect