Mode Of Action Of Antibiotics Flashcards
What type of cell wall is more susceptible to a/b
Gram +ve
Basic mechanism of antibiotics action (5)
Inihibition of cell wall synthesis
Inhibition of protein synthesis
Inhibition of nucleic acid synthesis
Inhibition of folic acid synthesis
Alteration off cell membrane
Inhibition of cell wall synthesis
b lactams
Bind penicillin binding proteins (pbps ) : enzymes responsible for peptudoglycan synthesis
Eg penicillins
Glycopeptides
Distrupt cross linkage of peptidoglycan layers
Eg vancomycin
What type of ribosomes are present in bacterial cell
70s
What type do ribosomes are present in eukaryotic cells
80s
What drugs affect protein synthesis of bacteria
Streptomycin /aminoglycosides
Effects of aminoglycosides on protein synthesis
Distrusts protein synthesis by binding to 70s ribosomes
Irreversibly binds to 30s subunit
Inhibits initiation of transcription leading to misreading of mRNA
Results in:
Shutdown of protein synthesis
Production of defective proteins
Effect of tetracyclines on protein synthesis
Inhibit 70s and 80s ribosomes but 70s ade more sensitive to tetracycline and antibiotic selectively taken uo by bacteria
Inhibitory action on 30s subunit
Types of drugs affecting cell wall synthesis
Aminoglycosides/ streptomycin Tetracyclines Macrolides Fusidic acid Clindamycin Chloramphenicol
How do quinolones work
Inhibit DNA gyrase. DNA gyrase needed for unwinding, replication, rewinding of circular suiercolied bacterial DNA
PREVENT DNA REPLICATION= cell death
What is folic acid needed form
Essential for formation of DNA and RNA. If you can stop bacteria synthesis if fundamental building blocks NA= cell death.
Folic acid synthesised by bacteria but not mammilian cells = selective toxicity
Examples of antibiotics which inhibit folic acid synthesis
Trimethoprim
What antibiotic alters cell membrane
Polymixin B
Disorganise membrane permeability
Leakage of nucleic acid and cations
Cell death
