Antibiotics Flashcards
What are the Mechanisms of Action
Inhibit/interfere with cell wall synthesis
Inhibit protein synthesis
Disrupt unique components of cytoplasmic membrane
Inhibit metabolic pathways
Inhibit nucleic acid synthesis
Why can we inhibit protein synthesis?
we have different ribosomes
B-Lactam Antibiotics
cephalosporin, monobactams, carbapenems
Inhibits peptidoglycan synthesis
bactericidal
Bacteria can produce b-lactamase, makes antibody resistant. What is the B-lactamase inhibitor that can overcome this resistance?
clavulanic acid
Glycopeptide Antibiotics
bactericidal
Vancomycin,
Prevents addition of new subunits of PD (peptidoglycan) to a growing cell wall
Linezolid
acts on initiation stage, Prevent formation of initiation complex
Tetracycline and Tigecycline
block the A site on the ribosome, preventing the binding of amino acids
Aminoglycosides
Interfere with proof reading
leads to increase rate of error in synthesis with premature termination
Chloramphenicol
Block peptide transfer step of elongation on 50S subunit in bacteria and mitochondria
Adverse affects of Chloramphenicol
Aplastic anemia, bone marrow suppression, leukemia, neurotoxicity
Benefit of Chloramphenicol
crosses blood brain barrier, if you get meningitis you need something that will cross
Macrolides, Clindamycin, and Amino Glycosides inhibit what?
ribosomal translocation
Daptomycin and Polymyxins
disrupt cell membrane
Polymixins: interact with phospholipids, poking holes in the cell MB
Inhibit Metabolic Pathways
Antifolates
Pyrimidine analogues
Purine analogues
Antifolates
we get them from our diet, we don’t make them
impair the function of folic acid leading to disruption in DNA/RNA production
Pyrimidine
disrupt their formation and DNA/RNA synthesis
Purine
disrupts nucleic acid production
Inhibit Nucleic Acid Synthesis: Rifampin
Bind to RNA polymerase, gets the transcript, blocks this at DNA level, Block RNA synthesis
Inhibit Nucleic Acid Synthesis: Quinolones
inhibit DNA Synthesis,
Nalidixic acid
Ciprofloxacin
Narrow spectrum drugs
limited, good for specific families of bacteria
can be gram negative OR positive
Broad spectrum drug
kills everything, ex: amoxicillin
can be BOTH gram -/+
good for drug resistant bacteria that do not respond to each other
Why have a broad spectrum?
If you don’t know what to kill, it kills everything (Bad and good)
Efficacy: Diffusion susceptibility test (Kirby Test)
Susceptible- Antibiotic works
- Resistant, doesn’t care that antibiotic is there, the bacteria will grow right up to the disk, does not work
- Zone of Inhibition
Minimum Inhibitory Concentration:
MIC
Minimum amount we need to inhibit the bacteria (minimum bactericidal)
- Tubes
- eTest
MBC: Minimal bactericidal concentration
Topical (superficial infections)
- Oral (lower drugs concentrations
- IM (intramuscular)
- Intravenous IV (highest conc) need to be shot straight into vessel
Safety and Side-Effects of MIC and MBC
Toxicity
Polymixins & aminogylcocides : can be fatal on kidneys
Metronidazole- Black Hairy tongue
Tetracycline: complex w/ calcium and get incorporated into growing bone/teeth (white spots on teeth)
Allergies: .1% of Americans have anaphylaxis to penicillin
What is bacterial transformation
Bacteria that happens to have a resistant gene. And this bacteria is dying, letting its parts out
Other bacteria is swimming around and incorporates the bad genes from the environment
What is bacterial transduction
Has to do with a virus, phagocytic virus transfers resistance
What is bacterial conjugation
Bacteria sex, is it has a pili and the other bacteria is capable to hooking up to the pili they can spread resistance gene (makes copy first)
Bacteria to bacteria
What is horizontal gene transfer
transfer of genes with the same generation
