What are the most common pediatric infections, their causative organisms, and recommended antibiotics?

Most Common Pediatric Infections, Causative Organisms, and Recommended Antibiotics

The most common pediatric infections include respiratory tract infections, urinary tract infections, skin and soft tissue infections, and gastrointestinal infections, with specific first-line antibiotics recommended for each based on the most likely causative organisms.

Respiratory Tract Infections

Upper Respiratory Tract Infections

• Acute Otitis Media

  • Organisms: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
  • Antibiotics: Amoxicillin (first-line) 45-90 mg/kg/day divided in 2-3 doses 1
  • Alternative: Amoxicillin-clavulanate for beta-lactamase producing organisms 2

• Sinusitis

  • Organisms: Streptococcus pneumoniae, Haemophilus influenzae
  • Antibiotics: Amoxicillin (first-line), second or third-generation cephalosporins (cefpodoxime, cefuroxime) 2
  • Alternative: Levofloxacin for resistant cases 2

Lower Respiratory Tract Infections

• Pneumonia

  • Age <3 years:

    • Organisms: Streptococcus pneumoniae (most common)
    • Antibiotics: Amoxicillin 80-100 mg/kg/day in three daily doses 2

  • Age >3 years:

    • Organisms: Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae
    • Antibiotics:
      • For pneumococcal pneumonia: Amoxicillin
      • For atypical pneumonia: Macrolides (azithromycin, clarithromycin) 2

• Bronchiolitis

  • Organisms: Primarily viral (RSV), rarely bacterial
  • Antibiotics: Generally not indicated; if bacterial superinfection suspected: amoxicillin-clavulanate, cefuroxime-axetil, or cefpodoxime-proxetil 2

Urinary Tract Infections

• Organisms: Escherichia coli (>80%), Klebsiella pneumoniae, Enterobacter species, Proteus species 3, 4
• Antibiotics:
  • Age 8-21 days: Ampicillin plus ceftazidime or gentamicin 2
  • Age 22-28 days: Ceftriaxone 2
  • Age >28 days: Ceftriaxone (IV/IM) or oral cephalexin/cefixime 2, 4
  • Third-generation cephalosporins show highest susceptibility (>92%) 4

Skin and Soft Tissue Infections

• Impetigo

  • Organisms: Group A Streptococcus, Staphylococcus aureus
  • Antibiotics: Dicloxacillin, cephalexin, clindamycin 2

• Cellulitis

  • Organisms: Group A Streptococcus, Staphylococcus aureus
  • Antibiotics:
    • For methicillin-susceptible S. aureus: Cephalexin (75-100 mg/kg/day) 2
    • For methicillin-resistant S. aureus: Clindamycin (30-40 mg/kg/day) 2

Gastrointestinal Infections

• Bacterial Gastroenteritis
  • Organisms: Salmonella species, Shigella species
  • Antibiotics: Ciprofloxacin (for severe cases) 2
  • Most cases are viral and don't require antibiotics

Intra-abdominal Infections

• Organisms: Mixed aerobic and anaerobic bacteria
• Antibiotics:
  • Mild-moderate: Ampicillin-sulbactam, amoxicillin-clavulanate
  • Severe: Piperacillin-tazobactam, ceftriaxone plus metronidazole, or carbapenems 2

Neonatal Infections (0-3 months)

• Organisms: Group B Streptococcus, E. coli, Listeria monocytogenes
• Antibiotics: Ampicillin plus gentamicin or cefotaxime 2

Conjunctivitis

• Organisms: Streptococcus pneumoniae, Haemophilus influenzae
• Antibiotics: Topical fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) 2

Key Considerations for Antibiotic Selection

1. Age-specific pathogens: Different organisms predominate at different ages, particularly in respiratory and systemic infections 2

2. Local resistance patterns: Regional antibiotic susceptibility should guide empiric therapy 4

3. Severity of infection: More severe infections may require combination therapy or broader-spectrum antibiotics 2

4. Route of administration: Oral therapy for mild-moderate infections; parenteral for severe infections or young infants 2

5. Beta-lactamase production: For organisms like H. influenzae and M. catarrhalis that may produce beta-lactamase, consider beta-lactamase inhibitor combinations 2

Antibiotic Dosing Considerations for Children

• Weight-based dosing is essential for pediatric patients to ensure appropriate drug concentrations
• Renal function must be considered, especially for aminoglycosides and certain beta-lactams
• Duration of therapy is typically 5-10 days for most common infections, with longer courses for more serious infections 2

Remember that judicious use of antibiotics is critical to prevent antimicrobial resistance, and viral infections (which constitute many pediatric respiratory illnesses) do not require antibiotic therapy.