Antibiotics Flashcards
What is the mechanism of TRP (trimethoprim)?
inhibit dihydrofolic acid reductase
synergistic with sulfonamides to kill E. coli
What is the mechanism of methotrexate?
inhibit dihydrofolic acid reductase
What is the mechanism of sulfonamides?
inhibit dihydropterase synthase in folate metabolsim (creation of dihydrofolic acid inhibited)
What is the mechanism of Vancomycin?
What is primarily used for?
Binds to D-ala D-ala residues on peptidoglycan to inhibit cell wall synthesis via blocking 1,4 glycosidic bond (at a step earlier than PCN)
Most tried and true for MRSA
What type of antibiotic is vancomycin?
What type of bugs does it target?
Glycopeptide
Gram positive- staphylococcus, streptococcus, enterococcus
What is the mechanism of Penicillin?
binds to penicillin binding proteins to inhibit cell wall synthesis (blocks the transpeptidation reaction which cross links peptidoglycan units in the cell wall)
penicillin is a structural analog for D-ala D-ala and irreversibly inactivates the transpeptidase enzyme
How is Penicillin resistance conferred?
Bacteria such as S. aureus which produce an enzyme called B-lactamase
- B lactamase cleaves the B-lactam ring of penicillin
Why are people commonly allergic to Penicillin?
Penicilloyl groups can act as haptens, which give rise to a hypersensitivity reaction via IgE immune activation
What is the mechanism of Methicillin?
What was the reason for its target?
Binds PBP2 therefore inhibiting cell wall synthesis
- MRSA (Methicillin resistant S. aureus) are resistant to being killed by methicillin because they encode a new PBP, PBP2a.
Methicillin is a semi-synthetic penicillin designed to evade destruction from B-lactamase produced by S. aureus
B lactam antibiotics with B lactamase inhibitors… what are they useful for and what are a couple of examples?
Combination of B lactam antibiotics with B-lactamase inhibitors are effective for Staphylococcal bugs
Piperacillin (for Pseudomonas)
Piperacillin/Tazobactam (Zosyn)
Ampicillin/Sulbactam (Unasyn)
Amoixcillin/Clavulanate (Augmentin)
How does Levofloxacin work (Fluroquinolone)
binds to DNA gyrase and prevents closure of DNA nicks, resulting in DNA fragmentation
How does Metronidazole work?
It is a prodrug which is activated by bacteria only (nitroreductase) to generate free radicals which non-specifically damage many cellular compartments including the chromosome
- activating agent nitroreductase is only expressed in anaerobic environment
How does Rifamycin work?
Selective for prokaryotic RpoB protein
Binds to the beta subunit of RNAP, specifically blocking initiation of transcription
inhibition of bacterial DNA-dependent RNA synthesis.[4] This is due to the high affinity of rifamycins for the prokaryotic RNA polymerase.
Treats mycobacterium tuburculosis
Which antibodies specifically target the 30s prokaryotic ribosome?
Spectinomycin - blocks translocation Tetracyclines - blocks aminoacyl-tRNA from binding to A-site, inhibits Eurkaryotic cells as well but not as much because eurkaryotic cells do not accumulate Streptomycin (aminoglycosides) - promotes miscoding errors, lethal
Which antibiotics target the 50s ribosome?
Chloramphenicol and clindamycin bind to 50s and block transpeptidation
macrolides (azythromycin)
