Antibiotics Flashcards
MoA of antibiotics that acting on cell wall synthesis
Inhibition of cell wall synthesis -> bacteria dies
2 examples of classes of the antibiotics that act on cell wall synthesis
- Beta-lactams: Penicillins, Cephalosporins
- Glycopeptides: Bacitracin
MoA of antibiotics disturb cell membrane
Antibiotic binds to the cell membrane ->altering its structure -> cell membrane becomes more permeable -> disruption of osmotic balance -> leakage of cellular molecules -> increase water uptake -> cell death
(2) examples of classes of antimicrobials that ac by disruption of a cell membrane
Polymyxins and Polyenes (anti-fungal)
(2) examples of antibiotics that act by preventing DNA from being synthesised
Examples: Quinolines, nalidixic acid
Example of antibiotic that act by preventing of RNA being synthesised
Rifamycin
Examples of antibiotics that disturb protein synthesis by targeting 50s unit of ribosome
50s subunit: Erythromycin, Chloramphenicol
Examples of antibiotics that target protein synthesis at 30s unit of ribosome (2)
30s subunit: Tetracycline, Streptomycin
General mechanism of action of protein synthesis inhibitors
Subunit targeted by an antibiotic -> disruption of
ribosomes -> bacteria unable to make proteins
-> bacteria can stay alive but is unable to do
anything
(Therefore these antibiotics are bacteriostatic -
prevent bacterial growth)
Mechanism of action of inhibitors of folic acid metabolism
- bacteria metabolise PABA (precursor) -> foliate (folic acid)
- folic acid is essential for the synthesis of: thymine and adenine (2 out of 4 nucleic acids that make up DNA)
Antibiotics:
PABA cannot convert into folic acid -> prevent
DNA synthesis
(2) examples of antibiotics that act as folic acid inhibitors
Sulphonamides, Trimethoprim
Mechanism of action of beta-lactams
Beta-lactams = Penicillins
Mechanism of action: inhibit cell wall synthesis = bactericidal
Mechanism of resistance to beta-lactams
Mechanism of resistance: production of beta - lactamases -> hydrolysis of beta - lactam -> antibiotic structure is broken -> drug inactivation
What drugs can overcome resistance from beta-lactamases?
Co-amoxiclav and Tazocin
Can inhibit beta-lactamase so can overcome resistance -> however have little antimicrobial effect -> given in combination with amoxicillin and Pipercillin
- mixed spectrum: gram positive and gram negative
MoA of cephalosporins
Cephalosporins = beta-lactams
MoA:inhibit cell wall synthesis = bactericidal