Antibiotics Flashcards
Define bacteriostatic antibiotics
Inhibit bacterial growth and proliferation
Define bacteriocidal antibiotics
Kill bacteria
What is an antibiotic’s “spectrum”?
The range of microorganisms over which it is effective
Can be narrow or broad
Describe the features of an ideal antibiotic
- Selective toxicity
- Bacteriocidal
- Long half life (persists)
- Good tissue distribution
- No side effects
- Both oral and parenteral preparations
Define selective toxicity
Where the antibiotic effects a function/structure exclusive to the microorganism
Thus only the microorganism is effected
List common antibiotic targets
- Cell wall (peptidoglycan synthesis)
- Ribosomes (protein synthesis)
- DNA replication
- DNA gyrases (chromosome folding)
- Metabolic pathways
Give the classes of cell wall antibiotics
- Penicillins (β-lactam)
- Cephalosporins (β-lactam)
- Glycopeptides
Describe the basic function of β-lactam antibiotics
- β-lactams bind irreversibly with Penicillin Binding Proteins (PBPs)
- Inhibits peptidoglycan synthesis
- Call wall compromised (cell death)
What are penicillin binding proteins (PBPs)?
Enzymes involved in peptidoglycan biosynthesis
Are β-lactam antibiotics bacteriocidal or bacteriostatic?
Yes
Give the positives of penicillin
- Few side effects
- Lots of possible drug variations
- Range of narrow and broad spectrum
- Bacteriocidal
- Has gram -ve and +ve affecting variants
Give the negatives of penicillin
- Patients can be allergic
- Resistance is common
- Rapid excretion (so more doses)
Give an example of a penicillin antibiotic that affects:
> Gram +ve
Gram -ve
GRam +ve and -ve
Gram +ve: Flucloxacillin
Gram -ve: Temocillin
+ve & -ve: Amoxicillin, Co-amoxiclav
Give an example of an antibiotic that is mixed with another compound to improve its effectivness
Co-amoxiclav
Amoxicillin mixed with clavulanic acid
Clavulanic inhibits β-lactamase
Give the positives of cephalosporin antibiotics
- Long half-life
- Few side effects
- Reduced allergy
- Resistant to β-lactamases
Describe the reason why cephalosporins are rarely used
- They are broad spectrum
- Kill off normal gut flora
- Allow C. difficile to dominate
Describe how glycopeptides antibiotics work
- Inhibit cell wall synthesis, reduce peptide crosslinking
- Bind to the peptide side chains of peptidoglycan
- Prevent it getting added to the cell wall
Give the positives of glycopeptide antibiotics
- Bacteriocidal
On what class of bacteria to glycoprotein antibiotics exclusively work?
Gram +ve
They are excluded by the outer membrane in gram -ve bacteria
Give the 3 main classes of antibiotics targeting protein synthesis
- Aminoglycosides
- Tetracyclines
- Macrolides
What is the mechanism of action for antibiotics that affect protein synthesis?
- Bind to ribosome
- Inhibit protein synthesis
Give an example of an aminoglycoside antibiotic
Describe it
Gentamicin
- Bactericidal
- Toxic
- Gram -ve
Describe tetracycline antibiotics
- Bacteriostatic
- Broad spectrum
- Reasonable level of resistance
- Destroys normal gut flora (e.g. secondary infections)
Describe macrolide antibiotics
- Bacteriostatic
- Excreted via the liver
