11. Antimicrobials

Question 1

How do beta-lactam antibiotics work?

Answer 1

Interfere with the synthesis of the bacterial cell wall peptidoglycan

1. Antibiotic binds to penicillin-binding protein on bacteria
2. Inhibit the transpeptidation enzyme
3. Disruption of bacterial cell wall structure

Question 2

What are the 3 main sub groups of beta-lactams?

Answer 2

Penicillins
Cephalosporins
Carbapenems

Question 3

Give examples of penicillins

Answer 3

Phenoxymethylpenicillin
Flucloxacillin
Amoxicillin
Co-amoxiclav

Question 4

What is co-amoxiclav?

Answer 4

Amoxicillin and clavulanic acid

Question 5

Give examples of cephalosporins

Answer 5

Cefalexin
Ceftriaxone
Cefuroxime
Cefotaxime

Question 6

Name some antibacterials that affect bacterial protein synthesis

Answer 6

Tetracyclines
Macrolides
Nitrofurans

Question 7

How do tetracyclines work?

Answer 7

Following uptake into susceptible organisms by active transport, they act by inhibiting protein synthesis

Question 8

Give examples of tetracyclines

Answer 8

Doxycycline

Tetracycline

Question 9

What are the clinical applications of tetracyclines?

Answer 9

Resp tract infections
Acne
Chlamydia
Lyme disease

Question 10

Who is tetracyclines not suitable for?

Answer 10

Children <12 years
Pregnant and breastfeeding women
Cause staining of developing teeth

Question 11

How do macrolides work?

Answer 11

Inhibit bacterial protein synthesis by an effect of ribosomal translocation

Question 12

Give examples of macrolides

Answer 12

Clarithromycin
Erythromycin
Azithromycin

Question 13

What are the clinical applications of macrolides?

Answer 13

Very similar to penicillin

Also active against atypical respiratory pathogens

Question 14

What is the most commonly prescribed nitrofuran?

Answer 14

Nitrofurantoin

Question 15

What is the mechanism of action of nitrofurans?

Answer 15

Works by being reduced to multiple reactive intermediates by nitrofuran reductase inside the bacterial cell
These then attack ribosomal and DNA proteins within the bacteria, as well as inhibit the citric acid cycle

Question 16

What is nitrofurantoin commonly used for?

Answer 16

UTI

Question 17

How do quinolones work?

Answer 17

Inhibit topoisomerase II, the enzyme that produces a negative supercoil in DNA and thus permits transcription or replication

Question 18

Give examples of quinolones

Answer 18

Ciprofloxacin

Levofloxacin

Question 19

What are quinolones used for?

Answer 19

Very good cover of gram negative organisms, as well as atypical organisms and gram positives
Complicated UTIs
Pseudomonas aeruginosa cover
Gonorrhoea

Question 20

What are the side effects of quinolones?

Answer 20

Tendinitis +/- rupture
Aortic dissection
CNS effects (convulsions)

Question 21

What are the example of antibacterial agents that interfere with folate synthesis or action?

Answer 21

Sulfonamides

Trimethoprim

Question 22

How does trimethoprim work?

Answer 22

Folate antagonist

Question 23

What are the clinical applications of trimethoprim,?

Answer 23

UTIs - careful when prescribing to reproductive age females

Question 24

What are the most commonly used antivirals?

Answer 24

Aciclovir (DNA polymerase inhibitors)

Oseltamivir

Question 25

What are the clinical applications of aciclovir?

Answer 25

Herpes simplex infections

Varicella zoster