AM - Definitions and Mechanisms

Question 1

What is Bactericidal?

Answer 1

Antimicrobial that kills bacteria

Question 2

What is Bacteriostatic?

Answer 2

Antimicrobial that inhibits the growth of bacteria

Question 3

Define sensitive

Answer 3

Organism is sensitive if it is inhibited or killed by the antimicrobial at the site of infection

Question 4

Define resistant

Answer 4

Organism is resistant if it is not killed or inhibited by the antimicrobial needed to kill a given organism

Question 5

Define Minimal Bactericidal Concenration

Answer 5

MBC is the minimum concentration of antimicrobial needed o kill a given organism

Question 6

Define Minimal inhibitory concentration

Answer 6

MIC is the minimum concentration of antimicrobial needed to inhibit growth of a given organism

Question 7

What are the routes of administration of antibiotics?

Answer 7

• Topical
• Systemic
• Parenteral

Question 8

Describe the topical route of administration of antibiotics.

Answer 8

Applied to surface e.g. skin or mucous membrane

Question 9

Describe the systemic route of administration of antibiotics

Answer 9

Taken internally (orally or parenterally)

Question 10

Describe the parenteral route of administration of antibiotics

Answer 10

• Administrated intra-venously (IV) or intra-muscularly (IM)

- Occasionally sub-cutaneously

Question 11

What are the mechanisms of action of antibiotics?

Answer 11

• Inhibition of cell wall synthesis
• Inhibiton of protein synthesis
• Inhibition of nuclei acid synthesis

Question 12

How does inhibition of cell wall synthesis work?

Answer 12

Disrupt peptidoglycan synthesis by inhibiting the enzymes (penicillin-binding proteins, PBPs), responsible for cross-linking the carbohydrate chains.

Question 13

Features of inhibition of cell wall synthesis

Answer 13

• Penicillins and Cephalosporins
• beta-lactam ring antibiitics
• bactericidal antibiotics
• effective mostly against gram-positive bacteria

Question 14

Describe benzyl penicillin

Answer 14

Many gram negative organisms are resistant against benzyl pencillin

Question 15

What is another type of inhibition of cell wall synthesis?

Answer 15

-Glycopeptides

Question 16

What do glycopeptides do?

Answer 16

• They have an inability to penetrate the gram negative cell wall and act only on gram positive organisms too
• not absorbed from the GI tract and are only given parenterally

Question 17

What are examples of glycopeptides?

Answer 17

Vancomycin and teicoplanin

• toxicity Is very common in vancomycin. Careful IV infusion in order to avoid local tissue damage, and ensure the concentration is high enough to be therapeutic but not toxic.
• Teicoplanin is less toxic than vancomycin and has the advantage of single daily dosing

Question 18

How does inhibition of protein synthesis work?

Answer 18

• Works by binding to the bacteria’s ribosomes.

- This prevents the tRNA from landing and adding its amino acid onto the growing protein

Question 19

Which antibiotics inhibit protein synthesis?

Answer 19

• Aminoglycosides
• Macrolides
• Tetracyclines
• Oxazolidinones
• Cyclic lipopeptide

Question 20

What do Aminoglycosides do in inhibiting protein synthesis?

example?

Answer 20

• concentration depended bactericidal antibiotics
• useful in the treatment of serious gram negative infection (eg coliform)
• e.g. Gentamicin. It is toxic and requires a careful dosing regime and monitoring of levels

Question 21

What do Macrolides do in inhibiting protein synthesis?

example?

Answer 21

• Concentration dependent bacterial, bactericidal, or bacteriostatic antibiotics
• Useful alternative to penicillins in treatment of Gram-positive infection in patients
• E.g. Erythromycin

Question 22

What do tetracyclines, oxazolidinone, cyclic lipopeptide do?

Answer 22

Treat gram-positive infections

Question 23

How does inhibition of nucleic acid synthesis work?

Answer 23

• Inhibit DNA synthesis directly or indirectly by interrupting the supply of precursors for DNA synthesis
• used orally as well as parenterally
• cannot be used in children (interference with cartilage growth)

Question 24

Which antibiotics inhibit nucleic acid synthesis?

Answer 24

Trimethoprim and fluoroquinolones

Question 25

What is inhibition of nucleic acid synthesis effective against?

Answer 25

Gram-negative organisms, including Pseudomonas

Question 26

What antibiotics inhibit cell wall synthesis?

Answer 26

Penicillins
Cephasporins
Glycopeptides