ANTIBIOTIC DRUG CLASSES AND MECHANISM

Question 1

What are the possible reasons for adverse reactions to antibiotics?

Answer 1

Membrane interacting antibiotics may interact with patient membranes at high concentrations
Breakdown and release of bacterial components can cause a reaction

Question 2

What is a narrow spectrum antibiotic?

Answer 2

Target narrow group of bacteria (e.g., gram +ve or Gram -ve)

Question 3

What is a broad spectrum antibiotic?

Answer 3

Targets Gram +ve ANd gram -ve

Question 4

What is a bacteriocidal antibiotic?

Answer 4

Kills organism
e.g., penicillin’s, cephalosporin’s

Question 5

What is a bacteriostatic antibiotic?

Answer 5

Drugs that temporarily inhibit the growth of an organism (i.e. reversible if removed).
Examples Tetracycline’s, Chloramphenicol

Question 6

What is the MIC of an antibiotic?

Answer 6

(minimum inhibitory concentration): The concentration required at the site of infection to achieve bacterial inhibition.

Question 7

What is the MBC of an antibiotic?

Answer 7

(minimum bactericidal concentration): The concentration required at the site of infection to kill the bacteria

Question 8

What are the different targets of antibiotics on bacteria

Answer 8

Inhibition of protein synthesis
Inhibition of cell membrane function
Inhibition of cell wall synthesis
Interference with other pathways
Inhibition of DNA dependent RNA polymerase
Disruption of DNA structure

Question 9

Give examples of antibiotics which inhibit protein synthesis

Answer 9

Chloramphenicol
Lincosamides
Macrolides
Amino glycosides
Pleuromutilin
Tetracyclines
Nitrofurans

Question 10

Give examples of antibiotics which inhibit cell membrane function

Answer 10

Polypeptides Antimicrobial peptides

Question 11

Give examples of antibiotics that inhibit cell wall synthesis

Answer 11

B-lactam antibiotics
Vancomycin
Bacitracin

Question 12

Give examples of antibiotics that inhibit DNA dependent RNA polymerase

Answer 12

Rifampicins

Question 13

Give examples of antibiotics that disrupt DNA structure

Answer 13

Nitroimidazoles
Metronidazole

Question 14

How do antibiotics inhibit cell wall synthesis

Answer 14

Targets peptidoglycan (unique to bacteria)
Lysozyme produced by host breaks bonds in polysaccharide
Beta-lactam inhibits penicillin binding protein (transpeptidase) weakening cell wall => increased osmotic pressure => burst
Glycopeptides cap peptide chains to weaken cell wall => bursts

Question 15

Describe how Beta-lactam antibiotics work

Answer 15

Penicillins (narrow and broad) and cephalosporins )1st - 5th gen)
Beta-lactam inhibits penicillin binding protein (transpeptidase) weakening cell wall => increased osmotic pressure => burst

Question 16

How do antibiotics inhibit protein synthesis

Answer 16

inhibit translation of RNA to proteins by binding to ribosomal complex

Question 17

How do aminoglycosides work?

Answer 17

Bacteriocidal
Inhibit protein synthesis by binding to 30S and effects a number of steps of protein synthesis leading to non-functional proteins
GRAM -VE

Question 18

How do tetracyclines work?

Answer 18

Bacteriostatic
Inhibit protein synthesis
Actively enter cell and bind to 30S subunit preventing tRNA attachment
GRAM -VE and +VE

Question 19

How does chloramphenicol work?

Answer 19

Bacteriostatic
Inhibits protein synthesis by binding to 50S subunit and preventing linkage of amino acids to growing peptides
Broad spectrum

Question 20

How do sulphonamides/trimethoprim (TMPS) work?

Answer 20

Affect DNA
Competitive inhibitors of dihydropteroate synthetase to inhibit dihydrofolate synthesis which is required for DNA synthesis

Question 21

How do Quinolones and Novobiocin work?

Answer 21

Affect DNA
Bind to and stops DNA Gyrase preventing packing of DNA, inhibits supercoiling of chromosome => disrupts associated processes

Question 22

How do Nitroimidazoles work?

Answer 22

Affect DNA
Reduction products are reactive with DNA causing DNA strands to break

Question 23

How does Rifampicin work?

Answer 23

~Inhibits DNA dependent RNA polymerase => blocks initiation of protein synthesis

Question 24

Describe the use of antimicrobial peptide

Answer 24

Topical application
Interact and disrupt membranes
Licensed for dermatology (ears)
Work via difference in charge

Question 25

How can the site of infection alter antimicrobial activity?

Answer 25

Aerobic vs anaerobic
Time
Concentration