Antibacterial drugs L7 Flashcards
antimicrobials=
a natural or synthetic chemical that kills or inhibits the growth of microorganisms
antibacterial agents=
antimicrobials that target
antibiotics=
antibacterial compounds produced by microorganisms (currently used to describe all antibacterial drugs)
narrow spectrum antimicrobials=
effective against a limited number of bacterial genera
Broad spectrum antimicrobials=
effective against a large number of bacterial genera
4 ideal anti-bacterial properties
- selective for microbial target
- Bactericidal (kills)
- Slow emergence of resistance
- narrow spectrum of activity
3 positives of broad spectrum
- empirical usage (when we don’t know whats happening
- polymicrobial infection
- companies prefer ($$)
negative of broad spectrum
resistance problems
list 5 pharmacological considerations when making drugs
- stability and retention in host
- Dosage and method of administering
- accumulation in various tissues and organs
- toxicity to host
- interference with other drugs
pharnacokinetics=
stability, retention and compartmentalisation of drug in host
MIC=
minimum inhibitory concentration value
3 ways to classify antibiotics
bactericidal or bacteriostatic
chemical structure
targets
best way to classify antibiotics
targets
differences in prokaryotic vs eukaryotic= (5)
cell wall synthesis cytoplasmic membrane anti-metabolites protein synthesis nucleic acid synthesis
peptidoglycan is found in what cells
unique to bacteria
in both gram + and -
what do beta lactams do
inhibit enzyme PBPs (penicillin binding proteins) which are required for the last step of peptidoglycan synthesis= transpeptidation
2 subtypes of beta lactams=
pencillins
cephalosporins
what do glycopeptides do
bind to peptidoglycan subunit so stops other units from being connected to the mesh
what are glycopeptides only effective against (+ or-)
gram positive
they do not penetrate gram -
e.g of glycopeptides
vancomycin
ribosomes in Eukaryotes
80s
40s+60s subunits
ribosomes in bacteria
70s (30s+50s subunits)
30s inhibitors= (2)
aminoglycosides
tetracyclines
50s inhibitors (4)
chloramphenicol
erythromycin
clindamycin
Oxazolidinoes
tRNA inhibitor= (2)
puromycin
Mupirocin
EF-G elongation factor
fusidic acid
are aminoglycosides bactericidal
yes
are Tetracyclines bactericidal
no they are bacteriostatic
what do Quinolones do
inhibit DNA replication
what do Rifamycins do
block mRNA synthesis
what do metabolite analogues do
inhibit the synthesis of nucelic acid precursors (purines and pyrimidines)
what are purines and pyrimidines made from
folic acid derivatives
whats different about folic acid uptake in bacteria and humans
bacteria carry out the process to make it themselves whereas humans take up folic acid from external sources
what do sulfonamides do to the folic acid pathway
competitive inhibitor with PABA for enzyme
what do trimethoprim do to the folic acid pathway
similar to dihydrofolic acid
what are polymyxins
act like a detergent on membrane
mainly topical usage (bc can affect human cell membrane)
why is the cytoplasmic membrane not a good target
because there isn’t enough difference in eukaryotic and prokaryotic cells
3 narrow spectrum antibiotics
older penicillins
macrolides
vancomycin
broad spectrum antibiotics
- aminoglycosides
- 2nd and 3rd gen cephalosporins
- synthetic penicillins
what is antibiotic resistance
relates to sensitivity to antibacterial agent at a certain concentration
3 classifications of antibiotic resistance
resistant
intermediate
sensitive
what is resistance judged by
MIC
explain minimum inhibitory concentration
minimum concentration of the antibacterial agent below which growth is not inhibited
innate resistance= (2)
lacks suitable target
impermeable to drug
3 major mechanisms of acquired resistance
1 non major
- Modifying the antibiotic target
- Limiting access of the antibiotic
- Enzymatic inactivation of antibiotic
- Bypass pathway
2 ways bacteria can become resistant to beta lactams
- produce and secrete enzyme beta-lactamase
2. alter the PBP so that the beta-lactam can not interact with it, yet retain function
2 ways resistance is acquired
horizontal gene transfer
mutations
what is MDR-TB resistant to
at least 2 first line TB drugs
what is XDR-TB resistant to
3 or more of the 6 classes of second line TB drugs
