Lecture 2: Antibiotics Part I Flashcards
How do beta-lactams work relative to bacterial physiology?
They latch onto transpeptidase enzymes (PBPs), then inhibit peptidoglycan synthesis (bacteriostatic) and cause cell wall to lyse (bactericidal)
AKA they inhibit bacterial wall synthesis
What ABX fall under beta-lactams?
PCNs
Cephalosporins
Carbapenems
Monobactams
What does a beta-lactam ring look like?
3 carbon 1 nitrogen square with a double bond to an O.
See slide 8 for visual.
What is the MOA of a beta-lactam?
- Drug binds to pencillin-binding proteins (PBP)
- This inhibits bacterial peptidoglycan synthesis, preventing bacterial replication. (Bacteriostatic)
- Binding to PBP activates bacterial autolytic enzymes that cause cell wall lysis. (Bacterioricidal)
How do G+ bacteria fight back against beta-lactams?
- Reduced binding affinity to PBPs.
- Productions of beta-lactamases to cleave the abx.
How do G- bacteria fight back against beta-lactams?
- Loss of outer membrane proteins.
- Beta-lactamases in periplasmic space.
What does penicillin become if the beta-lactam ring is broken?
Penicilloic acid
What is ABX resistance classified as?
Public Health Crisis!!!
2 millions infections
23,000 deaths
What are natural penicillins first-line for?
Group A Strep Throat
Syphilis (Treponema pallidum) (Spirochetes)
N. meningitis (sometimes)
What are some pros and cons of natural pcns?
Cons:
Susceptible to beta-lactamase
Tastes bad
Multiple doses required
Increasing resistance
Pros:
Cheap
Safe
What are antistaphylococcal PCNs indicated for as first-line?
SSTIs with S. aureus and staph epidermis
What are the antistaphylococcal PCNs?
Dicloxacillin
Nafcillin
Oxacillin
What is the purpose of methicillin?
Identifying microbial resistance.
DO NOT USE FOR TX.
What are aminopenicillins first-line treatment for?
Otitis Media:
H. influenzae
S. pneumoniae
Moraxella Catarrhalis (M. Cat)
Prophylaxis for endocarditis!
Which aminopenicillin is better for PO?
Amoxicillin. (also tastes like bubblegum so children will take it)
What is the main difference in coverage between natural PCNs and the aminoPCNs?
Increased G- coverage.
What are the advantages of AminoPCNs over natural PCNs?
Higher oral absorption and longer half-life = less frequent dosing.
Better G- coverage.
What are the PCN/Beta-lactamase inhibitor combos first-line for?
Augmentin (amoxicillin/clavulanic) is firstline for sinusitis, pneumonia/COPD exacerbations.
This includes S. pneumo, H. flu, and S. aureus.
How long should someone be on abx for a sinus infection?
At least 10 days, because sinus infections take longer to treat.
What are the considerations when RXing a PCN/Beta-lactamase inhibitor?
Increased Cost
Increase GI SE
Reserved for more severe infections.