IE antibiotics

Question 1

Penicillin (MOA, coverage side effect)

Answer 1

MOA:
Beta lactams –> binds to peptidoglycan in cell wall of gram +ve bacteria –> inactive enzymes in bacterial cell membrane –> prevents cell wall cross linking –> bactericidal = KILLS bacteria

Covers:
Gram +ve (except staph A.), some gram -ve, step, enterococcus

Side effect:
Rash, GI upset

Question 2

Name penicillin types and their coverage

Answer 2

1. Benzyl penicillin - narrow
   - Gram +ve (except staph A.), some gram -ve, step, enterococcus
2. Amoxycillin - moderate spectrum
   - Gram -ve, enterococci
3. Flucloxacillin (narrow spectrum)
   - methicillin, cloxacillin, dicloxacillin
   - -> penicillinase resistant beta lactam
   - -> anti staphylococcus Aureus (except MRSA) action
4. Beta-lactam + beta-lactamase inhibitor (clavulanate, sulbactam, tazobactam)
   - -> with penicillinase inhibitor
5. Penicillin with anti-pseudomonas
   - Carbenicillin, piperacillin, ticarcillin +/- clavulanate

Question 3

Aminoglycoside (gentamicin)

Answer 3

Aminoglycoside -> binds to ribosomal 30S subunit in bacteria -> inhibits protein synthesis -> bactericidal = KILLS bacteria

Gram -ve, HACEK, IE

S/E: ototoxicity, renal toxicity

Question 4

Vancomycin (Glycopeptides)

Answer 4

Prevent formation of peptidoglycan polymers -> inhibit bacterial cell wall synthesis -> bactericidal

Gram +ve (resistant to penicillin), anaerobes

Renaly clear

Question 5

HACEK

Answer 5

First line: ceftriaxone
Or one of the following:
• Ampicillin
• Ciprofloxacin

Question 6

Targeted

Methicillin-susceptible staphylococci (MSSA) & MRSA for NVE & PVE

Answer 6

MSSA:

• NVE: oxacillin (cephalosporin if penicillin allergy)
• PVE: nafcillin + gentamicin + rifampin

MRSA:

• NVE:
• PVE:

Question 7

Empiric Therapy

Answer 7

NVE:

• acute: vancomycin + cefepime
• subacute: vancomycin + ampicillin-sulbactam

PVE:

• <1 yr valv repl: vancomycin + gentamicin + rifampin + cefepime
• > 1 yr valv repl: vancomycin + ceftriaxone

Question 8

Empiric Therapy

Answer 8

NVE:

• acute: vancomycin + cefepime
• subacute: vancomycin + ampicillin-sulbactam

PVE:

• <1 yr valv repl: vancomycin + gentamicin + rifampin + cefepime
• > 1 yr valv repl: vancomycin + ceftriaxone