Antibacterial Drugs Flashcards
List the main targets for antibiotics
- cell wall synthesis (beta lactams such as penicillins and cephalosporins
- protein synthesis
- nucleic acid synthesis
- interference with metabolic pathways
- affect the cytoplasmic membrane
How do antibiotics prevent cell wall synthesis?
Beta lactams such as penicillins and cephalosporins work by inhibiting PBP’s
An example of a penicillin is amoxicillin
An example of a cephalosporin is cefuroxime
How do glycopeptide antibiotics function?
Binds to cell wall subunit and blocks new linkages
This class of antibiotics only affects gram positive bacteria
An example of this type of antibiotic is vancomycin
How do antibiotics affect protein synthesis?
Tetracyclines (bacteriostatic) and aminoglycosides (bactericidal) are 30s inhibitors
Macrolides are 50s inhibitors
TRNA inhibitors such as puromycin
EF-G elongation factor such as fusilic acid
How do antibiotics target nucleic acid?
Quinolones inhibit DNA replication such as ciprofloxacin
Rifamycins such as rifampicin block mRNA synthesis
How do antibiotics interference with metabolic pathways?
Sulfonamides compete for enzyme that DHF to THF
Trimethoprim inhibits the actual enzyme that catalyses the above reaction
THF is required for nucleic acid synthesis
How do antibiotics affect the cytoplasmic membrane?
Colistin is a polymyxin that acts as a detergent for bacterial cell membranes
Give three mechanisms of how antibiotic resistance comes about
Modifying the target so antibiotic no longer fits
Limiting the access of antibiotics by reducing penetration or increasing efflux
Enzymes that inactivate or cleave the antibiotic rendering it useless
What is the minimum inhibitory capacity
The minimum concentration of antibiotic which below growth is not inhibited
Examples of how bacteria have become resistant to beta lactams
Producing and secreting beta lactamase that inactivates the drug
By altering the structure of PBP
Acquired resistance occurs through two mechanisms:
Horizontal gene transfer = acquire genes that mediate resistance through plasmids or transposons (by coding for cleaving enzyme or efflux protein pumps)
Mutations of native genes or regulatory elements eg altering gyrases or making more efflux pumps
Mechanism of action of avibactam
Drug that inactivates beta lactamases that would mean beta lactams are still useful
