Intro to antibiotics

Question 1

What are the two types of antibiotics?

Answer 1

Bacteriostatic and bacteriocidal

Question 2

What is a bacteriostatic antibiotic?

Answer 2

Stops replication of bacteria

Question 3

What is a bacteriocidal antibiotic?

Answer 3

Kills the bacteria

Question 4

What is are the 6 parts of a bacterial cell that antibiotics can target?

Answer 4

1) Folic acid synthesis
2) DNA Damage
3) DNA Topisomerases
4) mRNA synthesis
5) Cell wall synthesis
6) Protein synthesis

Question 5

What is the importance of folic acid within bacteria?

Answer 5

Bacteria use folic acids in order to synthesize nucleic acids that make up their DNA.

Question 6

What are the two classes of antibiotics used to inhibit folic acid synthesis?

Answer 6

1) Sulfonamides

2) Trimethoprim

Question 7

What is the mechanism of action of Sulfamethoxazole?

Answer 7

It blocks the binding of PABA to pteridine, resulting in a pteridine-sulfa drug complex.

Question 8

What is the mechanism of action of Trimethoprim?

Answer 8

Blocks the production of tetrahydrofolic acid by inhibiting dihydrofolate reductase, therefore no folic acid.

Question 9

Why is THF (tetrahydrofolate) so important?

Answer 9

It is an essential factor needed for the production of thymidine which is required for synthesis of DNA and RNA.

Question 10

What are the two classes of antibiotics used to inhibit DNA Topoisomerases?

Answer 10

1) Fluoroquinolones

2) Quinolone

Question 11

What are the names of the drugs under the class ‘Fluoroquinolones’? (2)

Answer 11

Ciprofloxacin

Levofloxacin

Question 12

What is the name of the drug under the class ‘Quinolone’? (1)

Answer 12

Nalidixic acid

Question 13

What is the mechanism of action of DNA Topoisomerases inhibitors?

Answer 13

Binds to enzymes to prevent the separation of replicating DNA (Phosphodiester backbone).

Question 14

Which antibiotic causes the damage of bacterial DNA?

Answer 14

Metronidazole

Question 15

What type of antibiotic is it and what is the mechanism of action of ‘Metronidazole’?

Answer 15

Bacteriocidal
Damages microbial DNA and inhibits nucleic acid
Causes the formation of ROS which leads to DNA fragmentation.

Question 16

Which drug inhibits mRNA synthesis?

Answer 16

Rifampin

Question 17

What is the mechansim of action of Rifampin?

Answer 17

Inhibits transcription by targetting RpoB (encodes B-subunit of RNA polymerase).

Question 18

What are the names of the classes of antibiotics which inhibit protein synthesis in the 50S subunit of the bacteria? (2)

Answer 18

1) Macrolides

2) Streptogramins

Question 19

What are the names of the generic mRNA synthesis inhibitors, 50S (3)?

Answer 19

1) Chloramphenicol
2) Clindamycin
3) Linezolid

Question 20

What are the three drugs under the class ‘macrolides’?

Answer 20

1) Azithromycin
2) Clarithromycin
3) Erythromycin

Question 21

What are the names of the classes of antibiotics which inhibit protein synthesis in the 30S subunit of the bacteria? (2)

Answer 21

1) Aminoglycosides

2) Tetracyclines

Question 22

What are the 3 drugs under the class ‘Tetracyclines’?

Answer 22

Tetracycline
Doxycycline
Minocycline

Question 23

What is the mechanism of action of the ‘macrolides’?

Answer 23

They bind reversibly to the 50S subunit and prevent the transfer of peptidyl-t RNA from the A-site to P site, therefore inhibiting translocation.

Question 24

What is the mechanism of action of the ‘tetracyclines’?

Answer 24

It inhibits the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation.

Question 25

What is the mechanism of action of the 'aminoglycosides'?

Answer 25

Aminoglycosides bind to the 30s ribosomal sub-unit and cause a misreading of the genetic code. This subsequently leads to the interruption of normal bacterial protein synthesis.

Question 26

What are the class of antibiotics that inhibit peptidoglycan synthesis?

Answer 26

Glycopeptides

Question 27

What are the two drugs under the class 'glycopeptides'?

Answer 27

Vancomycin | Bacitracin

Question 28

What is the mechanism of action of 'Vancomycin'?

Answer 28

Inhibits the second stage of cell wall synthesis of susceptible bacteria by binding to D-Ala D-Ala

Question 29

What is the suffix of the class of antibiotics that inhibit ergosterol?

Answer 29

Azoles

Question 30

What is the mechanism of action of the 'Azoles?'

Answer 30

They inhibit 14-a demythylase which causes disruption of the cell wall.

Question 31

What is the name of the class of antifungals that inhibit cell wall synthesis?

Answer 31

Echinocandins

Question 32

Name two 'Echinocandins'

Answer 32

Caspofungin | Micafungin

Question 33

What is the mechanism of action of 'Echinocandins'? (Caspofungin)

Answer 33

Blocks the synthesis of β(1,3)-d-glucan of the fungal cell wall, by non-competitive inhibition of the enzyme β(1,3)-d-glucansynthase. β(1,3)-d-Glucanis an essential component of the cell wall of numerous fungal species.

Question 34

What is the name of the antibiotics that inhibit the formation of membrane pores?

Answer 34

Polyenes

Question 35

Name two 'Polyenes'

Answer 35

Amphotericin B | Nystatin

Question 36

What is the mechanism of action of Amphotericin B?

Answer 36

binds irreversibly to ergosterol, resulting in disruption of membrane integrity and ultimately cell death. Increase ROS entry

Question 37

What is the name of the drug that inhibits nucelic acid synthesis?

Answer 37

Flucytosine

Question 38

What is the mechanism of action of Flucytosine?

Answer 38

It is converted to fluorouracil by cytosine deaminase. This inteferes with RNA and protein synthesis?

Question 39

What is fluorouracil metabolised into that inhibits Thymydylate synthetase (prevents DNA synthesis)?

Answer 39

5-fluorodeoxyuridylic acid

Question 40

What are the 3 main resistance mechanisms of bacteria?

Answer 40

1) Efflux 2) Drug target 3) Degradation