Intro to antibiotics Flashcards
What are the two types of antibiotics?
Bacteriostatic and bacteriocidal
What is a bacteriostatic antibiotic?
Stops replication of bacteria
What is a bacteriocidal antibiotic?
Kills the bacteria
What is are the 6 parts of a bacterial cell that antibiotics can target?
1) Folic acid synthesis
2) DNA Damage
3) DNA Topisomerases
4) mRNA synthesis
5) Cell wall synthesis
6) Protein synthesis
What is the importance of folic acid within bacteria?
Bacteria use folic acids in order to synthesize nucleic acids that make up their DNA.
What are the two classes of antibiotics used to inhibit folic acid synthesis?
1) Sulfonamides
2) Trimethoprim
What is the mechanism of action of Sulfamethoxazole?
It blocks the binding of PABA to pteridine, resulting in a pteridine-sulfa drug complex.
What is the mechanism of action of Trimethoprim?
Blocks the production of tetrahydrofolic acid by inhibiting dihydrofolate reductase, therefore no folic acid.
Why is THF (tetrahydrofolate) so important?
It is an essential factor needed for the production of thymidine which is required for synthesis of DNA and RNA.
What are the two classes of antibiotics used to inhibit DNA Topoisomerases?
1) Fluoroquinolones
2) Quinolone
What are the names of the drugs under the class ‘Fluoroquinolones’? (2)
Ciprofloxacin
Levofloxacin
What is the name of the drug under the class ‘Quinolone’? (1)
Nalidixic acid
What is the mechanism of action of DNA Topoisomerases inhibitors?
Binds to enzymes to prevent the separation of replicating DNA (Phosphodiester backbone).
Which antibiotic causes the damage of bacterial DNA?
Metronidazole
What type of antibiotic is it and what is the mechanism of action of ‘Metronidazole’?
Bacteriocidal
Damages microbial DNA and inhibits nucleic acid
Causes the formation of ROS which leads to DNA fragmentation.
Which drug inhibits mRNA synthesis?
Rifampin
What is the mechansim of action of Rifampin?
Inhibits transcription by targetting RpoB (encodes B-subunit of RNA polymerase).
What are the names of the classes of antibiotics which inhibit protein synthesis in the 50S subunit of the bacteria? (2)
1) Macrolides
2) Streptogramins
What are the names of the generic mRNA synthesis inhibitors, 50S (3)?
1) Chloramphenicol
2) Clindamycin
3) Linezolid
What are the three drugs under the class ‘macrolides’?
1) Azithromycin
2) Clarithromycin
3) Erythromycin
What are the names of the classes of antibiotics which inhibit protein synthesis in the 30S subunit of the bacteria? (2)
1) Aminoglycosides
2) Tetracyclines
What are the 3 drugs under the class ‘Tetracyclines’?
Tetracycline
Doxycycline
Minocycline
What is the mechanism of action of the ‘macrolides’?
They bind reversibly to the 50S subunit and prevent the transfer of peptidyl-t RNA from the A-site to P site, therefore inhibiting translocation.
What is the mechanism of action of the ‘tetracyclines’?
It inhibits the binding of aminoacyl-tRNA to the mRNA-ribosome complex. They do so mainly by binding to the 30S ribosomal subunit in the mRNA translation.
What is the mechanism of action of the ‘aminoglycosides’?
Aminoglycosides bind to the 30s ribosomal sub-unit and cause a misreading of the genetic code. This subsequently leads to the interruption of normal bacterial protein synthesis.
What are the class of antibiotics that inhibit peptidoglycan synthesis?
Glycopeptides
What are the two drugs under the class ‘glycopeptides’?
Vancomycin
Bacitracin
What is the mechanism of action of ‘Vancomycin’?
Inhibits the second stage of cell wall synthesis of susceptible bacteria by binding to D-Ala D-Ala
What is the suffix of the class of antibiotics that inhibit ergosterol?
Azoles
What is the mechanism of action of the ‘Azoles?’
They inhibit 14-a demythylase which causes disruption of the cell wall.
What is the name of the class of antifungals that inhibit cell wall synthesis?
Echinocandins
Name two ‘Echinocandins’
Caspofungin
Micafungin
What is the mechanism of action of ‘Echinocandins’? (Caspofungin)
Blocks the synthesis of β(1,3)-d-glucan of the fungal cell wall, by non-competitive inhibition of the enzyme β(1,3)-d-glucansynthase. β(1,3)-d-Glucanis an essential component of the cell wall of numerous fungal species.
What is the name of the antibiotics that inhibit the formation of membrane pores?
Polyenes
Name two ‘Polyenes’
Amphotericin B
Nystatin
What is the mechanism of action of Amphotericin B?
binds irreversibly to ergosterol, resulting in disruption of membrane integrity and ultimately cell death. Increase ROS entry
What is the name of the drug that inhibits nucelic acid synthesis?
Flucytosine
What is the mechanism of action of Flucytosine?
It is converted to fluorouracil by cytosine deaminase. This inteferes with RNA and protein synthesis?
What is fluorouracil metabolised into that inhibits Thymydylate synthetase (prevents DNA synthesis)?
5-fluorodeoxyuridylic acid
What are the 3 main resistance mechanisms of bacteria?
1) Efflux
2) Drug target
3) Degradation
