Antibiotics

Question 1

Define bacteriostatic antibiotics

Answer 1

Inhibit bacterial growth and proliferation

Question 2

Define bacteriocidal antibiotics

Answer 2

Kill bacteria

Question 3

What is an antibiotic’s “spectrum”?

Answer 3

The range of microorganisms over which it is effective

Can be narrow or broad

Question 4

Describe the features of an ideal antibiotic

Answer 4

• Selective toxicity
• Bacteriocidal
• Long half life (persists)
• Good tissue distribution
• No side effects
• Both oral and parenteral preparations

Question 5

Define selective toxicity

Answer 5

Where the antibiotic effects a function/structure exclusive to the microorganism

Thus only the microorganism is effected

Question 6

List common antibiotic targets

Answer 6

• Cell wall (peptidoglycan synthesis)
• Ribosomes (protein synthesis)
• DNA replication
• DNA gyrases (chromosome folding)
• Metabolic pathways

Question 7

Give the classes of cell wall antibiotics

Answer 7

• Penicillins (β-lactam)
• Cephalosporins (β-lactam)
• Glycopeptides

Question 8

Describe the basic function of β-lactam antibiotics

Answer 8

• β-lactams bind irreversibly with Penicillin Binding Proteins (PBPs)
• Inhibits peptidoglycan synthesis
• Call wall compromised (cell death)

Question 9

What are penicillin binding proteins (PBPs)?

Answer 9

Enzymes involved in peptidoglycan biosynthesis

Question 10

Are β-lactam antibiotics bacteriocidal or bacteriostatic?

Answer 10

Yes

Question 11

Give the positives of penicillin

Answer 11

• Few side effects
• Lots of possible drug variations
• Range of narrow and broad spectrum
• Bacteriocidal
• Has gram -ve and +ve affecting variants

Question 12

Give the negatives of penicillin

Answer 12

• Patients can be allergic
• Resistance is common
• Rapid excretion (so more doses)

Question 13

Give an example of a penicillin antibiotic that affects:

> Gram +ve
Gram -ve
GRam +ve and -ve

Answer 13

Gram +ve: Flucloxacillin

Gram -ve: Temocillin

+ve & -ve: Amoxicillin, Co-amoxiclav

Question 14

Give an example of an antibiotic that is mixed with another compound to improve its effectivness

Answer 14

Co-amoxiclav

Amoxicillin mixed with clavulanic acid

Clavulanic inhibits β-lactamase

Question 15

Give the positives of cephalosporin antibiotics

Answer 15

• Long half-life
• Few side effects
• Reduced allergy
• Resistant to β-lactamases

Question 16

Describe the reason why cephalosporins are rarely used

Answer 16

• They are broad spectrum
• Kill off normal gut flora
• Allow C. difficile to dominate

Question 17

Describe how glycopeptides antibiotics work

Answer 17

• Inhibit cell wall synthesis, reduce peptide crosslinking
• Bind to the peptide side chains of peptidoglycan
• Prevent it getting added to the cell wall

Question 18

Give the positives of glycopeptide antibiotics

Answer 18

• Bacteriocidal

Question 19

On what class of bacteria to glycoprotein antibiotics exclusively work?

Answer 19

Gram +ve

They are excluded by the outer membrane in gram -ve bacteria

Question 20

Give the 3 main classes of antibiotics targeting protein synthesis

Answer 20

• Aminoglycosides
• Tetracyclines
• Macrolides

Question 21

What is the mechanism of action for antibiotics that affect protein synthesis?

Answer 21

• Bind to ribosome

- Inhibit protein synthesis

Question 22

Give an example of an aminoglycoside antibiotic

Describe it

Answer 22

Gentamicin

• Bactericidal
• Toxic
• Gram -ve

Question 23

Describe tetracycline antibiotics

Answer 23

• Bacteriostatic
• Broad spectrum
• Reasonable level of resistance
• Destroys normal gut flora (e.g. secondary infections)

Question 24

Describe macrolide antibiotics

Answer 24

• Bacteriostatic

- Excreted via the liver

Question 25

Give examples of antibiotics that affect nucleic acids

Answer 25

• Metronidazole
• Trimethoprim
• Fluoroquinolones

Question 26

List considerations when choosing an antibiotic

Answer 26

• Administration form
• Site of infection
• Likely infecting organisms
• Allergies
• Resistance
• Cost-effective