Antibiotics and Chemotherapy Flashcards
Broad-spectrum
effective against many species
Narrow-spectrum
Effective against few or single species
Source of antibiotics
- most discovered as natural producs
- often modified by artificial means
MIC
Minimum inhibitory concentration
lest amount of drug to block growth
MBC
Minimum bacterial concentration
least amount of drug to kill every living thing present
What test can you do to measure the MIC on a petri dish?
E-test strips, as they have a gradient of drug conentration
Tube dilution assay
- dilution sereis of drug
- drop of bacteria in tube with drug
- see growth (not inhibited) and no growth (inhibited visible growth)
- minimum concentration with no visible growth is MIC
- take tube with no drug, and transfer drop of all no growth tubes and see what does or does not grow
- minimum cencentration where bacteria does not grow in drug-free tube is MBC
-MBC is higher concentration than MIC
Examples of membrane-ative drugs
Polymyxin and Gramicidin
What does Polymyxin and Gramicidin do?
bind to phospholipids and lipid A to disrupt membranes
Nalidixic Acid
A subunit: Blocks nicking of DNA strands
Novobiocin
B subunit: Blocks ATP hydrolysis
Fluoroquinolones
- often given as broad-specrum antibiotics
- hits supercoiling
Rifampin
- Binds to RNA polymerase
- Specific for bacteria
- Prevents elongation of transcript after initiation (not used commonly)
- useful drug against Mycobacterium tuberculosis
What drugs target translation?
- Aminoglycosides
- Tetracycline – Blocks the A site
- Chloramphenicol – Binds 50S
- Erythromycin – 50S Subunit Near P Site
Oxazolidinones
prevent formation of the 70S ribosome initiation complex
Examples of Aminoglycosides
Streptomycin and Neomycin
Aminoglycosides binds to
30S
What does Tetracycline do?
- blocks the A site
- prevents tRNA from entering
- reversible
- bacteriostatic
What does Chloramphenicol do?
- binds to 50S
- blocks peptide bond formation
- prevent peptidyl transfer reaction
Macrolide example
Erythromycin
Erythromycin function
- prevents translocation
- 50S subunit near P site
An important carbon and hydrogen carrier
Tetrahydrofolate
Sulfa drugs are associated with the the blocking of
Tetrahydrofolate acid
Sulfa drug examples
Sulfanilamide and Trimethoprim
Isoniazid
- Mycolic acid formation inhibited
- This is one of the main anti-tuberculosis drugs
Fosphomycin
PEP Analog
- not used clinically due to toxicity
What kind of bacteria have mycolic acid?
Acid fast bacteria
Cross linking (peptidoglucan biosynthesis) is prevented by the
penecillins
D-cycloserine
D-alanine analog
- blocks pentapeptide formation
Lipid carrier inhibitors
- Vancomycin
- Bacitracin
Vancomycin
Prevents release from lipid carrier
- last drug resort, very toxic
Bacitracin
Blocks regeneration of carrier after release
- do not ingest
How does cross linking work
Beta-lactam drugs block
blocks transpeptidation
Characteristic of Beta-lactam
4 member ring
Examples of anti-fungal drugs
- Nystatin
- Imidazoles
- Amphotericin B
- Flucytosine
- Griseofulvin
Nystatin
Targets the membrane
Big difference between fungi and humans
humans - cholesterol
fungi - ergosterol
Imidazoles
- Inhibit sterol (ergosterol) synthesis
Amphotericin B
Flucytosine
Griseofulvin
- effective against ringworm
- prevents cell division
Anti-virals
- Amantadine
- Acyclovir
- Ribavirin
Amantadine
influenza A virus treatment (not as much anymore)
Acyclovir
- Herpesviruses
- Nucleoside analog
Ribavirin
blocks RNA synthesis
Anti-HIV agents target and inhibit
Reverse transcriptase and protease
Reverse transcriptase inhibitor
AZT
Protease inhibitor
indinavir
Antibiotics are ___ metabolites
secondary
Bacteria ___ some antibiotics
secrete
Bacteria can also make ___ to diable antibiotics
enzymes
What is the main problem iwth antibiotic use?
antibiotics are overused
Two main ways to become resistance
- do not interact with drug (barrier, destroy drug, etc.)
- change the target (alter so drug cannot effect target)
Watch lecture 20 through slide 32
Drug resistance can be aquired via…
horizontal gene transfer
How to fight drug resistance
- only use drugs when they are useful
- multidrug therapy
- dummy targets to inactivaate resistance enzymes
- alter antibiotic structure
if it ends in -cillin then it is a
beta lactam
Clarulanic acid binds to ____ so that S. aureus does not cleave ____.
Beta lactamase, amoxicillin