Antibacterials

Question 1

What are some targets for antibacterials?

Answer 1

DNA synthesis
Protein synthesis
Cell wall synthesis

Question 2

Name some antibacterials that target DNA synthesis.

Answer 2

Quinolones
- ciprofloxacin

Folic acid antagonists

• trimethoprim
• sulphonamides

Question 3

Name some antibacterials that target protein synthesis.

Answer 3

Aminoglycosides
- gentamicin (Can irreversibly damage CN VIII)

Macrolides
- erythromycin

Tetracyclines

Question 4

Name some antibacterials that target cell wall synthesis.

Answer 4

Beta-lactams

• penicillins
• cephalosporins
• carbapenems

Glycopeptides
- vancomycin

Question 5

How do we know if antibacterials will be effective?

Answer 5

Measure antibacterial activity:
- Disc sensitivity testing (Place discs of antibacterials on
plate of agar with bacteria on, measure distance from
disc that the antibacterial has killed.)
- E-tests

Question 6

What is the minimum inhibitory concentration?

Answer 6

Minimum Inhibitory Concentration (MIC)
- Minimum concentration of antibiotic required to inhibit
growth of a bacterium in vitro

Question 7

What is the breakpoint?

Answer 7

The concentration that can be achieved in vitro of an antibacterial
When used with the MIC it can predict the likely response of a bacterium:
- Susceptible
- Intermediate
- Resistant

Question 8

Explain the pharmacodynamics of antibacterials.

Answer 8

It is what the drug does to “the bacteria”

Time dependant killing:
- Successful treatment requires prolonged antibiotic
presence at site of infection
- But not high concentration
-Penicillins, cephalosporins, Glycopeptides

Concentration dependant killing
- Successful treatment requires high antibiotic 
  concentration at site of infection
- But not for long
- Aminoglycosides, quinolones

Question 9

What are some adverse reactions to antibacterials?

Answer 9

Hypersensitivity (allergy) (penicillin & cephalosporins)
C difficile (cephalosporins)
Renal (aminoglycosides)
Ototoxicity (aminoglycosides)
Nausea/vomiting/diarrhoea (tetracyclines/macrolides)
Liver (penicillins/cephalosporins/tetracyclines)
Bone marrow (chloramphenicol)
CNS toxicity (penicillins/carbapenems)
Electrolyte disturbances (penicillin)
Dental (tetracyclines)

Question 10

What is the point of therapeutic drug monitoring?

Answer 10

To ensure:

• Adequate dose
• Non-toxic dose

(aminoglycosides)
(vancomycin)

Question 11

What are some markers of potential antibacterial toxicity?

Answer 11

Creatine kinase (daptomycin)
Eosinophils (daptomycin)
Full blood count (linezolid, chloramphenicol)
Renal function (aminoglycosides)
Auditory function (aminoglycosides)
Stool chart (most antibacterials in hospital)

Question 12

Tell me about antibacterial resistance.

Answer 12

There is an ever increasing resistance to antibacterials emerging
Not multi-drug resistant (MDR)
- Includes non-susceptible to > 1 agent in > 2
antimicrobial categories

MDR
- Non-susceptibility to at least one agent in three or more antimicrobial categories

XDR (extensively drug resistant)
- Non-susceptibility to at least one agent in all but two or fewer antimicrobial categories

PDR (pan-drug resistant)
- Non-susceptibility to all agents in all antimicrobial categories