Chp 20 Flashcards
DONEDONEDONEDONEDONEDONEDONEDONEDONEDONE (25 cards)
Where do most antibiotics originate (nature vs synthesis)?*
Most originate naturally (penicillin) and some are made synthetically (sulfonamides)
Characteristics of an ideal antimicrobial drug.
- Selectively toxic (targets only pathogen and not host eg. penicillin targets cell wall which we do not have)
- Microbicidal (will KILL bacteria not just hold them like microbistatic)
- Remains potent long enough to act and is not broken down or excreted prematurely
- Reasonably priced
What are the 5 targets (mechanisms of action) of antibiotics? (first 3)
- Cell wall inhibitors (block synthesis and repair
- penicillin, cephalosporin, vancomycin (think PVC pipe) - Cell membrane: causes loss of selective permeability
- Polymyxins - DNA/RNA: stop replication and transcription
- Ciprofloxacin (one of the BEST antibiotics), fluoroquinolones
What are the 5 targets (mechanisms of action) of antibiotics? (last 2)
- Protein synthesis inhibitors acting on ribosomes
- Site of action 50s subunit
- Chloramphenicol, erythromycin, clindamycin, streptogramin (think SECCsy gramma for streptogramin heheeheheh)
- Site of action 30s subunit
- Aminoglycosides, gentamin, streptomycin, tetracyclines (does not allow tRNA to go to the active site) (think STAG the mice for streptomycin)
- both 30s and 50s
- Linezolid (Zyvox)
- Inhibit metabolic pathways and inhibit metabolism
- Sulfonamides
What are broad-spectrum and narrow-spectrum drugs?
Broad spectrum (large range): targets cell components common to MOST pathogens (eg ribosomes)
Narrow spectrum (smaller range): targets a specific cell component that is found only in certain microbes
Are penicillin and penicillin-like antibiotics more effective against actively growing cells, or old cells? Why?
They are more effective against actively growing cells since penicillin disrupts the cell wall, and growing cells are actively making their cell wall
How are semisynthetic drugs designed/synthesized?
You take a naturally occurring antibiotic and chemically modify it
eg. penicillin to ampicillin or amoxicillin
How do chloroquine and quinolones function as antimicrobial drug?
Chloroquine binds and cross-links the double helix while quinolones inhibit DNA helicases
If both eukaryotes and prokaryotes have ribosomes, why are antimicrobial that target ribosomes selectively toxic?
Eukaryotes have different size and structure from prokaryotes and antimicrobics usually have a selective actions against prokaryotes
How does Azidothymidine (AZT) function?
It inhibits HIV’s ability to replicate (thymine analog)
How do sulfonamides inhibit bacterial growth?
They block enzymes required for tetrahydrofolate synthesis needed for DNA and RNA synthesis
What do aminoglycosidases target?
The 30s ribosomal subunit
How does tetracycline function?
They block attachment of tRNA on the A acceptor site and stop further synthesis
Why is tetracycline not as commonly prescribed as penicillin?
It has more negative side effects than penicillin as well as increased resistance from bacteria
Why is selective toxicity so difficult to achieve in antiviral, antifungal, anti-protozoan, and antihelminthes?
It becomes more difficult to achieve as the characteristics of the infectious agent become more similar to the vertebrate host cell.
Describe five distinct ways bacteria may become resistant to antibiotics they were once sensitive to.
- Drug inactivation: develop enzyme and destroy antibiotic when it comes into contact (eg. penicillinase)
- Decreased permeability
- Activation of drug pumps
- Change in drug binding site
- Use of alternate metabolic pathway
Why are some drugs broad-spectrum and others narrow-spectrum?
Broad-spectrum antibiotics may be used when the specific type of bacteria causing the infection is unknown, while narrow-spectrum antibiotics are preferred when the causative bacteria is known
Are drugs that target the cell wall more or less selectively toxic than those that target the plasma membrane? Why?
The cell wall is only present in bacteria, not human cells, so it is already more selective in what cell it is killing
What is the advantage of using semisynthetic penicillin, like ampicillin or nafcillin?
They offer a broader spectrum than penicillin
What infections are aminoglycosidases used to treat?
Mainly those caused by gram negative bacteria
Why are antifungals generally more toxic to human tissues than antibacterial agents?
Fungi and human cells share more similarities which make it harder to selectively target fungi without harming the host
What drugs are used to treat malaria?
Quinine, chloroquinine, primaquine, mefloquine
Why is the fact that HIV is a retrovirus significant when designing antiviral therapies?
Its reliance on reverse transcriptase, provided a crucial target for the development of effective antiviral therapies
What are some of the antiviral drugs and their mode of action?
Oseltamivir good for tamiflu
tenofovir for HIV
