Beta Lactam Abx & Cell Wall Synthesis Inhibitors - Fitzpatrick Flashcards
Which natural penicillin can be given IV? PO?
IV or IM = pen G
PO = Pen V
which Anti-‘Staphylococcla’ can be given PO?
- Oxacillin
- Dicloxaillin
- Nafcillin (IV is also available: notice it’s name does not have an ‘o’ so its not just for oral)
Which extended spectrum penicillin can be given IV? PO?
IV = ampicillin PO = amoxicillin (the one with 'o' in it's name can be give PO)
what are the two anti-psudomonal commonly used?
Ticarcillin (taken with the beta lactamase inhibitor Clavulanic acid)
Pipercillin (taken with beta lactamse inhibitor Tazobactam)
In the cell wall biosynthesis of gram(+) bacteria such as strep, staph, and enterococci what is cross linked to a string of glycines?
Dipeptide D-ala-D-ala
what do beta lactams such as penicillins inhibit?
Beta lactams resemble D-ala-D-ala and they inhibit cross-linking enzymes/transpeptidases; and related penicillin binding proteins (PBPs) irreversibly
like penicillin, cephalosproins, carbapenems, monolactams also inhibits _
Peptidoglycan cross linking transpeptidase PBPs)
Penicillin G is indicated for what infections?
Gram (+) cocci:
1. Strep. pneumoniae (pneumococal pneumonia)
2. Strep. pyogenes (e.g. pharyngitis, scarlet fever)
(and others, don’t need to know for this test)
Pen G or V can be distributed to CNS only if _
inflamed meninges. Pen G/V cannot cross intact BBB
How is Pen G/V eliminated?
Renal tubular secretion
What is the main AE associated with Penicillin G/V?
Hypersensitivity –> anaphylaxis. Penicillin “hapten” reacts with proteins and on 2nd exposure to hapten provokes allergy/anaphylaxis in sensitized host (Type IV hypersensitivity)
Organisms resistant to penicillin do so by _
producing beta-lactamase (penicilllinase).
- the beta-lactam ring in penicillin G/V and some related penicillin confers vulnerability to drug resistance cuz it can be cleaved by beta lactamase thus inactivating penicillin G
What abx can be inactivated by beta lactamase enzymes?
- Natural penicillins such as G and V
- Extended spectrum: ampicillin, amoxicillin
- Anti-psudomonal: ticarcillin, piperacillin
What abx works well against organism that are resistant to penicillin G/V but sensitive to anti-spaphlococcal penicillins?
The anti-staph group of abx and they include: methicillin, nafcillin, oxacillin, and dicloxacillin (meth is not used anymore cuz it causes interstitial nephritis)
- they have chemical appendages that make them penicillin poor substrates for beta lactase and thus have excellent activity against staph aureus (aka Methicillin-sensitive S. aureus (MSSA)
How is nafcillin cleared and what AE are associated with it?
- Cleared via hepatic/biliary
- AE: hypersensitivity; increased P450 induction
How is oxacillin and dicloxicillin cleared and what are their AE?
- both cleared via renal/biliary
- AE for both is hypersensitivity
What is meant by MRSA and how is it acquired?
- (MRSA = Methicillin Resistance S. Aureus)
- Alteration of mec A gene and PBP 2 in S. aureus confers high level resistance to methicillin, oxacillin and other antistaph penicillins–despite the fact that they are not substrates for beta lactamase. This type of resistance is termed MRSA
True or false: methicillin resistance is caused by beta lactamase enzyme leading to MRSA
False. MRSA is caused by alteration of PBPs (PBP2). not beta lactamse enzymes
What is the drug of choice for MRSA?
vancomycin
What four main organisms is vancomycin used against?
- methicillin resistant s. aureus (MRSA)
- Methicilin resistant S. epidermis (MRSE)
- Enterococci (E. faecalis, E. Faecium)
- C. Difficile (if metronidazole fails)
what is the only time vancomycin is given orally?
To treat C. diff. All other times it’s given parenterally.
Vancomycin is NOT absorbed in the gut thus if given orally it will not treat infection in other other place besides the gut.
Pt is shown to have s.aureus infection. what is the best first line therapy for this pt?
- Anti-staphylococal penicillins such as nafcillin, oxacillin and dicloxacillin.
- ONLY if the s. aureus is resistant those the above, or if the pt is allergic to the above THEN give vancomycin.
Vancomycin is not a replacement for MSSA
what is the MOA of vancomycin?
vancomycin is a glycopeptide cell wall synthesis inhibitor. Glycopeptides abx such as vancoycin and teicoplanin, inhibit cell wall synthesis by binding the D-ala-D-ala and sterically hindering translycosylation and transpeptidation.
Vancomysin is not used for what strain of bacteria?
gram negative
