Week 3 - Cell Wall Inhibitors - Prunuske Flashcards
Explain the mechanism of Beta-lactam antibiotics:
Beta lactams basically bind to Penicillin Binding Proteins. These are the transpeptidases that cross-link peptidoglycans in cell wall synthesis.
Cell wall becomes weak and cell blows up!
Describe the penicillinase-resistant penicillins, aminopenicillins and anti-pseudomonal penicillins
Staphylococcal and Neisseria Gonorrhea inactivate penicillins by producing penicillinase.
Nafcillin and Dicloxacillin have larger R-groups, so are resistant to penicillinases. (For Gram +)
Ampicillin and Amoxicillin can do gram + and - because they are water soluble, but inactivated by beta-lactamase.
Ticarcillin and Piperacillin have broad activity against gram+, gram -, and pseudomonas. Can be inactivated by penicillinase.
List the combinations of inhibitors of β-lactamase with penicillins, their clinical usage & explain the reason why they are combined
Clavulanate irreversibly binds with penicillinase to deactivate it.
Sulbactam and Tazobactam do the same.
They are combined for different clinical effects to keep the antibiotic active
Describe the antimicrobial spectrum and pharmacokinetic properties of the four generations of cephalosporins
Cephalosporins are less susceptible to penicillinase, but can be inactivated by broader beta-lactamases.
1st : Gram +, dont cross BBB
2nd : Gram -, weak Gram +, don’t cross BBB
3rd : Serious Gram - infections, CAN cross BBB, watch out for C-Diff
4th : Gram+/-/pseudomonas, VERY broad
5th : MRSA destroyer
Explain the major side effects of penicillins and other beta-lactams including seizure, superinfection, and hypersensitivity
Penicillin and other beta lactams combine with your proteins to form a ‘hapten-protein’ complex that stimulates the immune system and results in production of specific antibodies to this antigen.
Describe the antimicrobial activity carbapenems and list the major side effects
Carbapenems are beta lactams, with resistance to beta lactamases. Imipenem/cilastatin, meropenem
Cilistatin is used with Impipenem to reduce inactivation and formation of a nephrotoxic metabolite. Could causes seizures, GI probs
Discuss the mechanism of action, spectrum, and side effects of polymyxin B and daptomycin
Polymyxin B :
- Binds to phosphatidylehtanolamine to make membrane holes
- Can kill mutli-drug resistant Gram(-) like pseudomonas
- Basically no resistance yet, can cause nephrotoxicity
Daptomycin:
Binds to cell membranes of gram+ bacteria to depolarize their membranes and kill
Great for gram(+) like MRSA
What families of drugs use beta lactam action?
Penicillin, cephalosporin, carbapenems, and aztreonam
Because penicillins often have a short half-life due to renal excretion. What drug can be simultaneously used?
Probencid!
allergic reaction to penicillin?
urticaria (hives), angiodema (skin swelling), anaphylaxis
3-10% of those in U.S. have experienced it, most don’t repeat
What drug should you use if the patient is allergic to penicillin?
Aztreonam, but ONLY for gram negative!
What is vacnomycin’s way of acting?
Inhibits an upstream reaction is the synthesis of the peptidoglycan cell wall. NOT BETA LACTAM
Not susceptible to beta lactamase. Great for Gram+ like C-Diff and MRSA.
How does Bacitran work?
Stops the bactoprenol carrier, which stops cell wall groth. NOT BETA LACTAM
Its nephrotoxic, so only given topically
