Antibiotics (Exam V) Flashcards
What are general properties of antimicrobial agent (5)?
- Selective Toxicity - bactericidal (kills) or bacteriostatic (slow growth)
- Spectrum of Activity - what types of organism (gram positive, gram negative, wide, narrow)
- Modes of Action
- Side Effects
- Resistance of Microorganisms
What are the 5 main modes of action with ABX and given examples. Essay Questions
- Inhibition of cell wall synthesis (gram +): PCN, bacitracin, cephalosporin, vancomycin)
- Disruption of cell membrane function (gram -): polymyxin
- Inhibition of protein synthesis (broadest group): Tetracycline, erythromycin, streptomycin, chloramphenicol
- Inhibition of Nucleic Acid synthesis: Rifamycin (transcription), Quinolones (DNA replication), Flagyl
- Block folic acid synthesis and inhibit metabolism: sulfanilamide, trimethoprim, Bactrim
Name two beta-lactamase inhibitors?
Why are beta-lactamase inhibitors sometimes given with PCN?
Clavulanic Acid
Sulbactam
Some bacterias can produce an enzyme call beta-lactamase which breaks the beta lactam ring of PCN.
By giving drugs like Sulbactam and Clavulanic Acid, the drug combo will result in bacteria’s sensitivity to penicillin.
What structure is highlighted in red below?
What two antibiotic have this structure?
What type bacteria will these drugs act on?
β-lactam ring
Penicillin and Cephalosporin
Gram (+) cocci and Anaerobes
How do β-lactam containing ABX’s inhibit cell wall synthesis?
- The β-lactam ring binds to enzymes that cross link the peptidoglycans that form the wall.
What drug is indicated by 1 on the figure below?
Penicillin
What drug is indicated by 2 on the figure below?
Cephalosporin
What type of bacteria do cell wall inhibitors work best on?
What type of bacteria do cell membrane disruptors work best on?
Gram +
Gram -
What are allergic reactions to PCN/Cephalosporins (5)?
- Anaphylactic shock (0.05%)
- Skin Rash (<1%)
- Oral Lesions
- Hemolytic Anemia
- Interstitial nephritis
What is the most common drug allergy that exists?
- Penicillin allergy (urticaria, redness, etc.)
- Can cross react with similar abx
What is an alternative to PCN?
Why?
Does it have better activity on gram positive bacteria?
Cephalosporins
Cephalosporins are more resistant to b-lactamase.
Cephalosporins have a broader spectrum.
Cephalosporins have less allergies than PCN.
First Gen Cephalosporins have better gram (+) activity.
Used for UTI and Staph
What drug is good alternative for penicillin resistant gram + bacteria (MRSA)? This is also the drug of last resort.
- Vancomycin (resistant to beta-lactamase)
What adverse reactions can occur from vancomycin (10% adverse reaction)?
- “Red-neck” Syndrome - neck flushing from histamine release
- Ototoxicity
- Nephrotoxicity
- Chills/fever
How do cell membrane disruptors work?
What is polymyxins effective against?
- Act as detergents essentially. Bind to phospholipids in membrane & create pores.
Very effective against gram (-) bacteria
How do tetracyclines work?
Pharmacokinetics of tetracyclines?
They inhibit protein synthesis (bacteriostatic)
Readily absorbed and widely distributed.