Antibiotics

Question 1

What is an antibiotic?

Answer 1

Agents produced by micro-organisms that can kill/inhibit the growth of other micro-organisms

Question 2

Where on bacteria does penicillin bind?

Answer 2

Bacterial Cell wall

Question 3

What are the 2 types of bacteria?

Answer 3

1) Bactericidal: AB kill bacteria by inhibiting cell wall synthesis
2) Bacteriostatic: Prevent bacteria growth by inhibiting DNA synthesis

Question 4

Define the Minimum Inhibitory Concentration

Answer 4

Lowest concentration of a chemical that prevents the growth of a bacterium

Question 5

Does the lowest MIC indicate the best antibiotic?

Answer 5

Many other factors also have to be considered e.g. number of binding sites and length of occupancy

Question 6

What does a drug have to do to ensure it inhibits any metabolic processes?

Answer 6

1) Occupy enough binding sites

2) Occupy the binding sites for long enough amount of time

Question 7

What is concentration dependent killing? (CDK)

Answer 7

Antibiotics that eradicate pathogenic bacteria through achieving high concentrations at site of binding (Peak Conc: MiC)

Question 8

What is time dependent killing? (TDK)

Answer 8

Time that serum concentrations remain above MIC, t>Mic

Question 9

Give examples of antibiotics which demonstrate each of the types of dependent killing?

Answer 9

CDK: Aminoglycosides e.g. Gentamicin
TDK: Beta Lactams e.g. Penicillin

Question 10

What are the 4 main mechanisms of antibiotic resistance?

Answer 10

1) Change antibiotic target
2) Destroy antibiotic
3) Prevent antibiotic access
4) Remove antibiotic from bacteria

Question 11

What are examples for 4 mechanisms of ABR?

Answer 11

1) Target mutation so AB can’t attach to the bacteria e.g. MRSA
2) Beta Lactam ring e.g. Penicillin can be destroyed which is essential for AB effect
3) Modifying membrane porin channel size, number and selectivity
4) AB removed via efflux pumps

Question 12

What are the 2 ways that antibiotic resistance develops?

Answer 12

1) Acquired: Spontaneous mutation/Horizontal Gene Transfer

2) Intrinsic: Natural resistance

Question 13

What method causes AB resistance via spontaneous mutation?

Answer 13

1) Change in AA sequence and cell structure
2) Decrease affinity of antibiotic resistance
3) New Nucleotide base pair

Question 14

What are 3 methods of horizontal gene transfer?

Answer 14

1) Transduction (Bacteriophage)
2) Conjugation (Bacterial Sex)
3) Transformation

Question 15

What are clinical examples of gram positive and negative bacteria?

Answer 15

1) Gram Positive: MRSA (Plasmid transfer resistance)

2) Gram Negative: ESBL (mutation at active site)

Question 16

What are the 3 main purposes of antibiotics?

Answer 16

1) prophylaxis
2) Avoid infections in surgery
3) Treatment

Question 17

When would flucloxacillin be given?

Answer 17

Someone infected with Staph. Aureus (MSSA)

Question 18

When would penicillin be given and what is an advantage of it?

Answer 18

Given: Skin, soft tissue infections and endocarditis
Adv: Narrow spectrum –> Reduced chance of resistance

Question 19

How is amoxicillin given and in what conditions?

Answer 19

Given: Orally or Intra-venously
Conditions: H.influenzae, enterococci, e.coli, shigella, streptococci etc.

Question 20

What does vancomycin work against?

Answer 20

Gram positive bacteria

Question 21

What are carbapenems?

Answer 21

Class of highly effective antibiotic agents to treat severe bacterial infections

Question 22

What are carbapenemases used for?

Answer 22

Enzymes which break down carbapenems and prevent them from working, causing antibiotic resistance