Chapter 38. Infectious Diseases

Ampicillin

Gram-positive organisms (Streptococcus spp.)

Susceptible Escherichia coli

Listeria monocytogenes

Empiric treatment for early- or late-onset (age >72 hrs) sepsis:

• ≤7 d old: 150 mg/kg/dose IV q12h
• >7 d old: 75 mg/kg/dose IV q6h

Treatment >48 h:

• Meningitis or no CSF obtained: 75 mg/kg/dose IV q6h
• Sepsis without meningitis: 75 mg/kg/dose IV q12h

Piperacillin

Pseudomonas aeruginosa Enterococcus spp.

Other Gram-negative enteric and anaerobes

PCN-susceptible Staphylococcus spp.

Streptococcus spp.

• ≤7 d: 50 mg/kg/dose q8h
• >7 d: 50 mg/kg/dose q6h

Moderate CSF penetration

Penicillin GK

GBS

Treponema pallidum

GBS meningitis:

• ≤7 d postnatal age: 450,000 units/kg/d divided every 8 h
• >7 d postnatal age: 450,000–500,000 units/kg/d divided every 4 h

Other GBS infections: 200,000 units/kg/d divided every 6 h

Nafcillin

Methicillin-sensitive Staphylococcus aureus

Non-CNS infections:

• <30 wk postmenstrual age (PMA):
  • ≤7 d: 25 mg/kg/dose q12h
  • >7 d: 25 mg/kg/dose q8h
• 30–37 wk PMA:
  • ≤7 d: 25 mg/kg/dose q12h
  • >7 d: 25 mg/kg/dose q8h
• >37 wk PMA:
  • ≤7 d: 25 mg/kg/dose q12h
  • >7 d: 25 mg/kg/dose q6h

Meningitis:

• Use 50 mg/kg/dose at same interval as listed above

Cleared primarily by the liver → monitor LFTs on treatment

Can cause interstitial nephritis → monitor renal function weekly on treatment

Can cause bone marrow suppression → monitor CBC weekly on therapy

Vancomycin

Aerobic and anaerobic Gram-positive cocci and bacilli

Methicillin-resistant S. aureus (MRSA)

Coagulase-negative staphylococci

Clostridium difficile

Bacillus spp.

Ampicillin-resistant Enterococcus

• <30 wk PMA:
  • ≤7 d: 20 mg/kg/dose IV q24h
  • >7 d: 20 mg/kg/dose IV q18h
• 30–37 wk PMA:
  • ≤7 d: 20 mg/kg/dose IV q18h
  • >7 d: 15 mg/kg/dose IV q12h
• >37 wk PMA:
  • ≤7 d: 15 mg/kg/dose IV q12h
  • >7 d: 15 mg/kg/dose IV q8h
• >44 wk PMA (meningitis):
  • 15 mg/kg/dose IV q6h

Only 10%–15% of serum concentration enters CSF.

Optimal serum concentration:

• Trough: 15–20 mcg/mL

Gentamicin, amikacin, tobramycin

Broad Gram-negative bacillus coverage

Synergistic against S. aureus, GBS, L. monocytogenes, enterococci

Gentamicin

• Indications: early- or late-onset sepsis (age >72 h); covers Gram-negative rods; use for synergy
  • <35 wk PMA: 3 mg/kg/dose IV q24h
  • ≥35wk PMA: 4 mg/kg/dose IV q24h
• If given >48 h (>2 doses), draw gentamicin trough before and peak level after the third dose. Monitor BUN/Cr:
  • Optimum levels: peak= 5–10 mcg/mL, trough = <1.5 mcg/mL
• For SYNERGY (against S. aureus, Enterococcus):
  • 1–1.5 mg/kg/dose IV q24h

Tobramycin

• <30 wk PMA:
  • ≤7 d: 3 mg/kg/dose q24h
  • >7 d: 3 mg/kg/dose q18h
• 30–37 wk PMA:
  • ≤7 d: 3 mg/kg/dose q18h
  • >7 d: 2.5 mg/kg/dose q12h
• >37 wk PMA:
  • ≤7 d: 2.5 mg/kg/dose q12h
  • >7 d: 2.5 mg/kg/dose q8h
• Optimum levels: peak = 8–10 mcg/mL; trough = <2 mcg/mL

Amikacin

• <30 wk PMA:
  • ≤7 d: 15 mg/kg/dose q24h
  • >7 d: 15 mg/kg/dose q18h
• 30–37 wk PMA:
  • ≤7 d: 15 mg/kg/dose q18h
  • >7 d: 15 mg/kg/dose q12h

CSF penetration depends on meningeal inflammation.

Monitor peak and trough levels, as these antibiotics can cause nephrotoxicity and ototoxicity.

• >37 wk PMA:
  • ≤7 d: 15 mg/kg/dose q12h
  • >7 d: ...