Antibiotic Resistance

Question 1

Explain selection pressure on bacteria in the presence of antibiotics

Answer 1

Bacteria exposed to antibiotics encourages resistance as small numbers of bacteria are “resistant mutants”. These survive whilst others die off from antibiotics (“survival of the fittest”)

Question 2

How do bacteria acquire resistance?

Answer 2

Result of change in bacterial DNA
2 mechanisms:
1. Genetic mutation
2. Transfer of resistant DNA from one bacterium to another by

Question 3

How do genetic mutations for antibiotics occur?

Answer 3

Bacteria reproduce rapidly so lots of chances for “misreading” of genetic code when replicating

Question 4

What are the 3 ways DNA mutations can be transferred between bacteria?

Answer 4

Transformation
Conjugation
Transduction

Question 5

What is transformation?

Answer 5

When bacteria die and the cells break apart, “free-floating” DNA released into surrounding environment and “scavenged” by other bacteria

Question 6

What is conjugation?

Answer 6

When two bacteria are in close proximity they form a hollow bridge between the two cells known as a pilus which allows transfer of plasmids

Question 7

What is transduction?

Answer 7

Infection of the bacteria with a virus containing bacterial DNA. Viruses are called bacteriophages or phages.

Question 8

What are the 3 mechanisms of antibiotic resistance?

Answer 8

Altered antibiotic target binding site
Destruction or inactivation of the antibiotic
Increased efflux

Question 9

How do beta-lactamases inactivate antibiotics?

Answer 9

Specifically target and disrupt the beta-lactam ring of these antibiotics

Question 10

What are ESBLs and how do they work?

Answer 10

Extended spectrum beta-lactamases (ESBLs) are enzymes that inactivate almost all the penicillins and cephalosporins