week 5 Flashcards
selective toxicity
ability of a drug to kill or inhibit pathogen while damaging host as little as possible
therapeutic dose
drug level required for clincial treatment
toxic dose
drug level at which drug becomes too toxic for patient
therapeutic index
ratio of toxic dose to therapeutic dose
- want this to be as large as possible
side effects
undesirable effects of drug on host cells
narrow spectrum drugs
attack a few specific organsims
broad spectrum drugs
attack a wide range of organisms
Minimal inhibitory concentration (MIC)
lowest concentration of drug that inhibits growth of pathogen
Minimal lethal concentration (MLC)
lowest concentration of drug that kills pathogen
how to measure MIC?
dilution susceptibility test- drug with lowest concentration showing no growth
what does MIC stand for
minimal inhibitory concentration
Disk diffusion test
measures different disks with antimicrobial agents on agar
- zones of inhibition = effective antibiotic
What are the targets of antibiotics
inhibitors of cell wall synthesis
protein synthesis inhibitors
metabolic antagonists
nucleic acid synthesis inhibition
Penicillin
- effective on gram positive bacteria
- blocks the enzyme that catalyzes transpeptidation
(formation of cross links in peptidoglycan)
prevents the synthesis of complete cell walls= cell lysis
cephalosporins
similar to penicillin
- broad spectrum (negative + positive)
Vancomycin and Teicoplanin
binds to peptidoglycan structure
gram positive antibiotic
- inhibit cell wall synthesis
Aminoglycosides
antibacterial against gram negative aerobic and facultative anaerobic bacteria
- binds to 30S ribosomes, interferes with protein synthesis by inhibiting the process and causing the misreading of the mRNA
Tetracyclines
four ring structure with varying side chains attached
- broad spectrum, bacteriostatic
- inhibits binding of aminoacyl - tRNA molecules to A site of ribosome
Macrolides
broad spectrum, bacteriostatic
binds to 23S rRNA and 50S ribosomal subunits
- inhibits peptide chain elongation
Trimethoprim
broad spectrum
interferes with folic acid production
sulfa drugs
selectively toxic due to competitive inhibition of folic acid synthesis enzymes
- bacteriostatic
Quinolones
-broad spectrum
-acts by inhibiting bacterial DNA gyrase and topoisomerase II
- bactericidal
Lipopeptides
very effective against gram positive organisms
- inserts into membrane near phoshatidylglycerol, then aggregates, changing membtrane curvature and allowing little holes to form
this depolarizes membrane
