Antibiotics Flashcards
What is the chemotherapeutic index?
Chem Index = maximum tolerated dose / minimal effective dose
What is an antibiotic?
A substance produced by a living organism that inhibits other microorganisms growth/reproduction
What is a chemotherapeutic agent?
An artificially created antimicrobial substance
How do you measure bacteriostatic activity? (antibiotic susceptibility)
MIC (minimal inhibitory concentration)
How do you measure bactericidal activity? (antibiotic susceptibility)
MBC (minimal bactericidal concentration)
List bacteriostatic antibiotics:
- macrolides
- tetracyclines
- chloramphenicols
- sulfonamides
List bactericidal antibiotics:
-beta-lactams
- aminoglycosides
-rifamycins
-glycopeptides
fluoroquinolones
What do aminoglycosides typically target?
Gram negative bacteria (usually aerobic)
ex. streptomycin (in TB)
What is the mode of action of aminoglycosides?
Inhibit protein synthesis by binding to the 30S ribosomal subunit
What are adverse effects of ahminoglycosides?
- ototoxicity (ear)
- nephrotoxicity
How are aminoglycosides administered?
Given parenterally
–> injection or infusion
How can you determine MIC?
Use the E-test
What is the E-test?
A quantitative test for antimicrobial susceptibility and MIC in gram + and -ve aerobic bacteria
- Combines the dilution and diffusion method
Give examples of fastidious bacteria
Anaerobes:
- n. gonorrhea,
- s. pneumoniae,
- streptococcus
What is the Kirby Bauer test?
Agar diffusion test
–> To test the bacteria’s sensitivity to antibiotic
What is the zone of inhibition?
The area where the antibiotic has killed the bacteria in an agar diffusion test
–> the larger the “ring” the more the antibiotic diffused and stopped growth/killed the bacteria
Explain the diffusion test:
- Make bacterial lawn from McFarland sample on agar plate
- Place paper discs w/ antibiotics on lawn
- Incubate overnight 37 degrees
- Look @ inhibition zones (different mm indicate susceptibilities)
Where do you find the MIC in an E- test?
Where the edge of inhibition ellipse intersects the side of the strip
List the 30S ribosomal subunit protein synthesis inhibitors:
- aminoglycosides
- tetracyclines
List the 50S ribosomal subunit protein synthesis inhibitors:
- macrolides
- lincosamides
- streptogramins
- chloramphenicol
- oxazolidinones
