T4L10 - Antimicrobial chemotherapy

Question 1

Erysipelas

Answer 1

Skin infection by Streptococcus pyogenes

Question 2

Facial crysipelas

Answer 2

Reconcentrated drug from urine

Question 3

Penicillin

Answer 3

Original = Benzylpenicillin (G)
Act on transpeptidases (peptidoglycans synthesis)
Functional unit = Beta Lactam

Question 4

Naturally occurring penicillin

Answer 4

Methicillin - not clinically used, only as a lab test

Flucloxacillin - mainly for S. aureus

Good for Staph, Streps, Neisseria

Question 5

Methicillin

Answer 5

Methicillin - not clinically used, only as a lab test

Flucloxacillin - mainly for S. aureus

Question 6

Flucloxacillin

Answer 6

Flucloxacillin - mainly for S. aureus

Question 7

Pseudomonas

Answer 7

Gram negative rod, causes wound infections

Antipseudomonal penicillins (e.g piperacillin)

Question 8

Antipseudomonal penicillins

Answer 8

piperacillin

Question 9

Beta lactamase inhibitors

Answer 9

• Clavulinic acid
Protect the antibiotic from degradation
Co-amoxiclav = amoxicillin plus clavulinic acid

Question 10

Staphylococcus aureus drug resistance

Answer 10

Mediated by beta-lactamase enzymes

Hydrolyses beta-lactam ring

Many Gram negatives (e.g. E. coli) make beta lactamases too

Question 11

MRSA

Answer 11

Encoded by mecA gene - probably acquired from other species of Staphylcoccus

mecA encodes a different transpeptidase enzyme

A ‘penicillin-binding protein’ which doesn’t bind penicillins
• Resistant to all beta-lactam antibiotics

Question 12

Bacteria sensitive to penicillin

Answer 12

S. pyogenes

Gram +ve and neisseria

Question 13

Gram +ve and penicillin

Answer 13

Most make beta lactamase or develop resistance through efflux pumps

Question 14

Mechanisms of resistance

Answer 14

• Enzymatic degradation of the drug
• Target modification
• Efflux of antibiotic from the bacteria
Reduced penetration through the cell wall

Question 15

Beta lactam antibiotics

Answer 15

Cephalosporin - acremonium

	○ Altered water solubility
	○ Delayed excretion
	○ Activity against transpeptidases of different bacterial species Resistance to degradation by bacterial ‘beta-lactamases’

Question 16

Cell wall

Answer 16

Beta lactamase
Glycopeptide
Lipopeptides

Question 17

Protein synthesis

Answer 17

Macrolides 
Lincosamides 
Chloramphenicol 
Aminoglycosides
Tetracycline

Question 18

Dna replication

Answer 18

Quinolones

Metronidazole

Question 19

RNA replication

Answer 19

Rifamycin

Question 20

Antimetabolites

Answer 20

Trimethoprim

Sulphonamides