Lecture 13: Mechanisms of Action of Antibiotics Flashcards
To choose an appropriate antimicrobial therapy, what two factors relating to the infecting species must be known?
Identity
Suscpetibility
What is empiric therapy?
If/when the identity of the infecting organism cannot be identified
Goes with most likely to cause infection, most likely susceptible
What is AST? Why is it performed?
Antimicrobial sensitivity testing
Choose best drug
What factors about the patient must be considered in choosing an appropriate antimicrobial therapy?
History (adverse reaction to drug), Age (and related symptoms/complications), pregnancy, renal and hepatic function (filtration), site of infection
What are pharmacodynamics? What four stages does it include?
How the body manipulates drug Absorption Distribution Metabolism Excretion
What are pharmacodynamics?
Biochemical and physiologic effects of drug
mechanism of action on bacteria
What are bacteriostatic agents?
stop growth; don’t kill
What are bacteriocidal agents?
irreversible damage; death
What class of agent are Beta-lactam antibiotics?
Bacteriocidal
What does the Minimal Inhibitory Concentration (MIC) of an antimicrobial agent mean?
Can be bacteriostatic at low concentrations, but bacteriocidal at higher concentrations
What do broad spectrum antibiotics target?
both G+ and G-
How are broad spectrum antibiotics used?
Empirically before causative bacteria is known
What is an example of a narrow spectrum antibiotic?
Vancomycin - G- only
What are the two most common antibiotic mechanisms of action?
- Inhibit peptidoglycan synthesis (cell wall)
2. Interfere with protein synthesis
What do antibiotic inhibitors of cell wall assembly interfere with?
Peptidoglycan synthesis
murein assembly
What do Beta-lactam antibiotics inhibit?
Cell wall synthesis
What are examples of beta-lactam antibiotics
penicillins
cephalosporins
monobactams
carbapenems
What does vancomycin inhibit?
Cell wall synthesis
What is the repeating unit of peptidoglycan?
NAG-NAM
What enzyme catalyzes cell wall synthesis and is a target of some antibiotics? What kind of enzyme is it?
Penicillin Binding Proteins (PBP)
Transpeptidase enzyme
How do beta-lactam antibiotics work?
mimics residue which would normally bind to active site of Penicillin Binding Proteins (transpeptidase enzyme)
irreversible
What are extended-spectrum cephalosporins?
resistant to destruction by most beta-lactamases
How are cephalosporins categorized by generation?
each generation has increased spectrum of activity
each generation has increased resistance to destruction to destruction to beta-lactamase enzymes
What kind of bacteria produce beta-lactamase enzymes?
G-
Which generations of cephalosporins are extended spectrum?
3 and 4
What does ESBL stand for?
Estended Spectrum Beta-Lactamase
Which two classes of antibiotics are resistant to destruction (effective against) EBSLs?
3rd and 4th generation cephalosporins
carbapenems
What are the 5 main mechanisms of antibiotics? (Interfere with…)
cell wall synthesis protein synthesis cytoplasmic membrane function nucleic acid synthesis matabolic pathway
What are the three ways antibiotics can inhibit protein synthesis?
interfere with formation of 30S initiation complex
interfere with formation of 70S ribosome
block elongation process of making peptide