Antibiotic Action

Question 1

What are the three classes of antibiotic which inhibit cell wall synthesis?

Answer 1

Penicillin, cephalosporins, glycopeptides

Question 2

What are the three mechanisms of antibiotic action?

Answer 2

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

Question 3

What are penicillin and cephalosporins ?

Answer 3

B-lactams

Question 4

What effect on a bacterium do antibiotics which act on the cell wall have?

Answer 4

Bactericidal effect

Question 5

Which type of bacteria are effected by antibiotics which inhibit cell wall synthesis?

Answer 5

Gram positive

Question 6

What is an example of a glycopeptide and what does it do?

Answer 6

Vancomycin - inhibits precursors of peptidoglycan so cell wall cant be synthesised

Used instead of b-lactams in bacteria which are resistant and produce b-lactamase

Fights MRSA

Question 7

Which antibiotic class inhibits protein synthesis in gram negative bacteria?

Answer 7

Aminoglycosides.

Question 8

What is an example of an aminoglycoside and what does it do?

Answer 8

Gentamicin - causes mis-reading on RNA and thus incorrect protein synthesised

Question 9

Which antibiotic can be used instead of penicillin and what form of action does it take on which bacteria?

Answer 9

Macrolides. Bactericidal and bacteriostatic action on gram positive bacteria. Used for people with penicillin allergies

Question 10

An example of a macrolide and its purpose

Answer 10

Erythromycin Treats abnormal pneumonia

Also substitution for penicillin in people with allergies

Question 11

Example of oxazolidinones and form of action (3)?

Answer 11

Linezolid. Inhibit protein synthesis in gram positive. Static or cidal. Treats MRSA and pneumonia

Question 12

What is a cyclic lipopeptide and an example? What does it treat?

Answer 12

Bactericidal on gram positive, inhibiting protein synthesis. Bactericidal. E.G. daptomycin

Serious skin infections or Severe sepsis by gram + bacteria

Question 13

Which class of antibiotics can inhibit nucleic acid synthesis?

Answer 13

Fluoroquinolones

Question 14

Which bacteria do fluoroquinolones act against and by which mechanism? What is an example?

Answer 14

Gram negative - bactericidal. Levofloxacin or Ciprofloxacin

Question 15

What is ciprofloxacin used for? How is it administered?

Answer 15

A fluoroquinolone to treat pseudomonas infections. Only oral solution

Question 16

What are tetracyclines and a use?

Answer 16

Inhibits protein synthesis in gram positive bacteria. Bacteriostatic. Treats chlamydia. Not for children under 12 or pregnant women

Question 17

Administration and side effects of linezolid

Answer 17

Orally. Cause bone marrow suppression. Treats MRSA

Question 18

Which drug is used when a patient has a very severe or high risk, complicated bacterial infection?

Answer 18

Carbapenems

Question 19

What is an emerging issue with use of carbapenem?

Answer 19

In many countries CPE is becoming more prominent (CPE is bacterium that produce carbapenemase which breaks down carbapenems) (CRE is just bacteria which are resistant to carbapenems)

Question 20

What is a carbapenem?

Answer 20

A b-lactam which is used to combat multi drug resistant (MDR) bacteria

Question 21

What is b-lactamase?

Answer 21

Bacterial enzymes which break the b-lactate ring of antibiotics and render them inactive

Question 22

How can we combat b-lactamase?

Answer 22

Administering co-amoxiclav (amoxicillin + clavulanic acid, a b-lactamase inhibitor)

Question 23

Which bacteria are b-lactamases found in?

Answer 23

Gram positive and negative bacteria

Question 24

How is resistance to b-lactams developed on a cellular level?

Answer 24

Penicillin binding site is mutated on bacterium so it can no longer bind, so

Question 25

What’s an example of a bacteria that is immune to b-lactams and what can be used instead?

Answer 25

MRSA. Vancomycin

Question 26

What is gentamycin and what is it used for?

Answer 26

Aminoglycoside, treats gram N, bactericidal. Little resistance in UK

Question 27

When do we use aminoglycosides and why?

Answer 27

We use aminoglycosides like gentamycin for serious gram negative bacteria because it is toxic

Question 28

What is the therapeutic margin?

Answer 28

Small therapeutic margin = small difference between effective and toxic dose. Must be monitored closely

Question 29

Why must age be considered when prescribing antibiotics?

Answer 29

In kids some may affect cartilage development

Question 30

Which antibiotics are safe to use in pregnancy?

Answer 30

Penicillin and cephalosporins

Question 31

How must antibiotic intake be altered in patients with renal failure or compromised liver?

Answer 31

Must be decreased or another therapy used. Antibiotics are excreted in kidneys and metabolised in liver

Question 32

What is the spectrum of an anti microbial agent?

Answer 32

The range of microbes which it may attack

Question 33

Mono therapy vs combination therapy + benefits

Answer 33

Monotherapy is the use of 1 antimicrobe. Combination may use +1. Can have a synergistic effect or an antagonistic effect

Question 34

What may lead to synergistic or antagonistic effects in combination therapy?

Answer 34

2 static/2 cidal = synergistic 1 static + 1 cidal = antagonist

Question 35

What is the M.I.C. And how do we measure it?

Answer 35

Minimum inhibition concentration. Minimum drug required to inhibit growth of bacteria. Measure this with E test

Question 36

What happens when an organism has an M.I.C different to the nationally agreed level?

Answer 36

Higher means its resistant to the drug and lower means its sensitive to the drug

Question 37

Name the 5 antibiotics which inhibit protein synthesis in bacterium.

Answer 37

Aminoglycoside Macrolide Tetracycline Oxazolidonone Cyclic lipopeptide

Question 38

When is flucloxacillin used?

Answer 38

Used for staph and strep gram positive skin infections. It’s a b-lactam