Antibacterials/Antibiotics

Question 1

What are the main classes of antibacterial drugs based on their targets?

Answer 1

• Inhibitors of folate synthesis & action
• Inhibitors of cell wall synthesis
• Inhibitors of protein synthesis
• Inhibitors of DNA synthesis

Question 2

What are examples of anti-folate drugs?

Answer 2

Sulfanilamide, trimethoprim

Question 3

Why is folate necessary?

Answer 3

Folate is necessary in humans and bacteria for DNA synthesis.

Question 4

Difference between humans and bacteria when it comes to folic acid synthesis

Answer 4

Bacteria make their own folic acid HOWEVER humans do not synthesize folic acid; instead, they have specific uptake mechanisms to transport it into cells.

Question 5

Why does the difference in folic acid synthesis between humans and bacteria matter for drug selectivity?

Answer 5

Because it allows the drugs to target bacteria without affecting human cells—this is called SELECTIVE TOXICITY .

Question 6

What does sulfanilamide (a sulfonamide) inhibit?

Answer 6

inhibits dihydropteroate synthetase, which is important for the initial step of folic acid synthesis.

It is able to do this because it is an analogue to PABA

( NOTE: image on top from note that implies sulfanilamide inhibits Pteridine synthetase BUT image on bottom indicates sulfanilamide inhibits dihydropteroate synthetase WHICH is what was mentioned in the slides)

Question 7

What is sulfanilamide structurally similar to?

Answer 7

It is a structural analogue to PABA.

Question 8

What does trimethoprim inhibit?

Answer 8

Inhibits dihydrofolate reductase and thus DNA synthesis.

Question 9

What is co-trimoxazole composed of?

Answer 9

sulfamethoxazole and trimethoprim.

Question 10

What are the different types of antibiotics that inhibit bacterial cell wall synthesis?

(Inhibitors of cell wall synthesis)

Answer 10

• β-lactam antibiotics (e.g., penicillins, cephalosporins)

• Glycopeptides (e.g., vancomycin)

Question 11

What are examples of β-lactam antibiotics?

Answer 11

Penicillins

Amoxicillin

Cephalosporins

Question 12

What is an example of a glycopeptide antibiotic?

Answer 12

Vancomycin

Question 13

What is the bacterial cell wall made of?

Answer 13

Peptidoglycan

Question 14

Do eukaryotic cells have peptidoglycan?

Answer 14

No

Question 15

What is the mechanism of action of β-lactam antibiotics?

Answer 15

(Two mechanism of action)

1. They inhibit cell wall synthesis by inhibiting bacterial transpeptidase enzymes responsible for cross-linking peptide chains of peptidoglycan.

AND

2. They cause the cell to lyse (cell lysis) by inactivating inhibitors of bacterial autolytic enzymes in the cell wall.
   (Basically they indirectly activate these bacterial autolytic enzymes in the cell wall)

Question 16

What class of antibiotics does vancomycin belong to?

Answer 16

Glycopeptides

Question 17

What is the mechanism of action of vancomycin?

Answer 17

It inhibits bacterial cell wall synthesis by binding to the D-Ala-D-Ala region of peptidoglycan subunits, inhibiting their release from the cell membrane carrier and preventing cross-linking.

(Simple explanation: Vancomycin blocks cell wall building by sticking to parts of the wall-building blocks, which stops them from linking together and forming the wall)

Question 18

What are two main classes of antibiotics within the β-lactam group and examples ?

Answer 18

Penicillins : penicillin & amoxicillin

Cephalosporins: cefotaxim

Question 19

What is a common issue with penicillins and cephalosporins?

Answer 19

Resistance

Question 20

What is the main cause of resistance to penicillins and cephalosporins?

Answer 20

Inactivation of the drug by β-lactamases

Question 21

Which β-lactam antibiotics are resistant to β-lactamases?

Answer 21

Aztreonam and meropenem

Question 22

How can resistance to β-lactam antibiotics be overcome?

Answer 22

By giving them with a β-lactamase inhibitor (e.g., clavulanic acid)

Question 23

What is clavulanic acid?

Answer 23

β-lactamase inhibitor

Question 24

Does clavulanic acid have antibiotic activity on its own?

Answer 24

No

Question 25

What is clavulanic acid structurally similar to?

Answer 25

β-lactams

Question 26

What does clavulanic acid inhibit?

Answer 26

Many β-lactamases

Question 27

How is clavulanic acid usually given?

Answer 27

In combination with hydrolyzable β-lactams For example: Co-amoxiclav = amoxicillin + clavulanic acid

Question 28

True or False: Vancomycin is a bactericidal antibiotic.

Answer 28

True

Question 29

How does vancomycin change cell wall permeability?

Answer 29

By binding to precursors of cell wall synthesis and inhibiting peptidoglycan elongation (Mechanism of action as well)

Question 30

Besides affecting the cell wall, what else does vancomycin inhibit?

Answer 30

RNA synthesis (Additional mechanism of action)

Question 31

Summary of all of the mechanism of actions for vancomycin (spread all over the note)

Answer 31

• It changes cell wall permeability by inhibiting peptidoglycan elongation • It binds to the D-Ala-D-Ala region of peptidoglycan subunits, preventing cross-linking • It inhibits RNA synthesis

Question 32

Where does protein synthesis occur?

Answer 32

In the ribosomes

Question 33

What are the bacterial ribosome subunits?

Answer 33

30S and 50S

Question 34

What are the mammalian ribosome subunits?

Answer 34

40S and 60S

Question 35

Why is the difference in ribosomal subunits between bacteria and humans important?

Answer 35

It allows for selective toxicity

Question 36

What are the different classes of antibiotics that inhibit bacterial protein synthesis? (Inhibitors of protein synthesis)

Answer 36

• Tetracyclines (e.g. doxycycline) • Aminoglycosides (e.g. streptomycin) • Amphenicols (e.g. chloramphenicol) • Macrolides (e.g. erythromycin) • Lincosamides (e.g. clindamycin) • Oxazolidinones (e.g. linezolid)

Question 37

Doxycycline is what type of protein synthesis inhibitor?

Answer 37

A tetracycline

Question 38

Streptomycin is what type of protein synthesis inhibitor?

Answer 38

aminoglycoside

Question 39

Chloramphenicol is what type of protein synthesis inhibitor?

Answer 39

amphenicol

Question 40

Erythromycin is what type of protein synthesis inhibitor?

Answer 40

macrolide

Question 41

Clindamycin is what type of protein synthesis inhibitor?

Answer 41

lincosamide

Question 42

Linezolid is what type of protein synthesis inhibitor?

Answer 42

oxazolidinone

Question 43

Are tetracyclines bacteriostatic or bactericidal?

Answer 43

Mostly bacteriostatic, but at high concentrations they can be bactericidal. (Read the picture if you don't know the difference)

Question 44

What is the mechanism of action of tetracyclines?

Answer 44

They inhibit bacterial protein synthesis by REVERSIBLY binding to the 30S ribosomal subunit.

Question 45

What is a side effect of tetracyclines

Answer 45

Drug deposition in bone and teeth, causing yellow or brown discoloration. (Missing slide showed more side effects like photosensitivity, hepatotoxicity, and teratogenic)

Question 46

What are examples of aminoglycosides?

Answer 46

Gentamicin and streptomycin

Question 47

Are aminoglycosides (i.e streptomycin) bacteriostatic or bactericidal?

Answer 47

Bactericidal

Question 48

What is the mechanism of action of aminoglycosides?

Answer 48

They inhibit bacterial protein synthesis by binding IRREVERSIBLY to the 30S ribosomal subunit.

Question 49

What is the mechanism of action of chloramphenicol?

Answer 49

Inhibition of mitochondrial protein synthesis by binding to the 50S ribosomal subunit

Question 50

Why is the use of chloramphenicol limited? When should chloramphenicol be used?

Answer 50

Due to serious side effects Only during life-threatening infections

Question 51

What are the serious side effects of chloramphenicol?

Answer 51

Gray baby syndrome in neonates (fatal) Serious hematological effects ( due to inhibition of mammalian mitochondrial protein synthesis)

Question 52

Gray baby syndrome in neonates is a fatal complication of which drug ?

Answer 52

chloramphenicol

Question 53

What are examples of macrolide antibiotics?

Answer 53

Erythromycin, azithromycin, and clarithromycin

Question 54

Are macrolides (i.e clarithromycin) bacteriostatic or bactericidal?

Answer 54

Bacteriostatic

Question 55

What is the mechanism of action of macrolides?

Answer 55

They inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit

Question 56

What is an example of a lincosamide antibiotic?

Answer 56

Clindamycin

Question 57

Is clindamycin ( a lincosamide) bacteriostatic or bactericidal?

Answer 57

It can be either, depending on the dose and the organism’s susceptibility.

Question 58

What is the mechanism of action of clindamycin ( a lincosamide) ?

Answer 58

It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.

Question 59

What is an example of an oxazolidinone antibiotic?

Answer 59

Linezolid

Question 60

Is linezolid ( an Oxazolidinone) bacteriostatic or bactericidal?

Answer 60

Bacteriostatic

Question 61

What is the mechanism of action of linezolid ( an Oxazolidinone) ?

Answer 61

It inhibits bacterial protein synthesis by interfering with assembly of the 30S and 50S ribosomal subunits.

Question 62

What are the types of antibiotics that inhibit DNA synthesis? (Inhibitors of DNA synthesis)

Answer 62

• Quinolones (e.g. ciprofloxacin) • Nitroimidazoles (e.g. metronidazole)

Question 63

What is an example of a quinolone antibiotic?

Answer 63

Ciprofloxacin

Question 64

What is an example of a nitroimidazole antibiotic?

Answer 64

Metronidazole

Question 65

Ciprofloxacin belongs to which subclass of antibiotics?

Answer 65

Fluoroquinolones (Quinolones)

Question 66

What type of activity do fluoroquinolones like ciprofloxacin have? bacteriostatic or bactericidal?

Answer 66

Concentration-dependent bactericidal activity

Question 67

What is the mechanism of action of fluoroquinolones?

Answer 67

They inhibit DNA replication by inhibiting DNA gyrase (topoisomerase II) and topoisomerase IV, leading to cell death

Question 68

Why don’t fluoroquinolones affect human DNA topoisomerase?

Answer 68

Because human DNA topoisomerase is structurally different and not sensitive to these drugs

Question 69

What class of antibiotic does metronidazole belong to?

Answer 69

Nitroimidazoles

Question 70

Is metronidazole (a Nitroimidazole) bacteriostatic or bactericidal?

Answer 70

Bactericidal

Question 71

What is the mechanism of action of metronidazole (a Nitroimidazole) ?

Answer 71

The reduced (active) form of the drug binds to DNA and inhibits DNA synthesis in anaerobic bacteria.