What is the antibiotic of choice for various bacterial infections?

Antibiotic Selection for Common Bacterial Infections

The optimal antibiotic selection for bacterial infections should follow the WHO AWaRe framework, prioritizing Access group antibiotics as first-line therapy due to their favorable risk-benefit profiles and lower resistance potential, while reserving Watch and Reserve group antibiotics for specific indications or when resistance is suspected. 1

WHO AWaRe Framework for Antibiotic Selection

• Antibiotics are categorized into three groups: Access (green), Watch (orange), and Reserve (red), using a traffic-light approach to guide appropriate use 2
• Access group antibiotics have good clinical activity against commonly susceptible bacteria with lower resistance potential and should be widely available in all healthcare facilities 2, 1
• Watch group antibiotics have relatively higher risk of selecting for antibiotic resistance and should be key targets of antibiotic stewardship programs 2
• Reserve group antibiotics should only be used as last-resort options when other alternatives are inadequate or have failed 2, 1

First-Line Antibiotics for Common Bacterial Infections

Respiratory Tract Infections

• Community-acquired pneumonia:

  • Children under 3 years: Amoxicillin 80-100 mg/kg/day in three daily doses is the reference treatment for pneumococcal pneumonia 2
  • Children over 3 years: Amoxicillin for pneumococcal infection; macrolides for atypical pathogens (Mycoplasma pneumoniae, Chlamydia pneumoniae) 2
  • Duration: 10 days for pneumococcal pneumonia, at least 14 days for atypical pneumonia 2

• Acute bronchitis:

  • Children under 3 years: Beta-lactams (amoxicillin, amoxicillin-clavulanate, cefuroxime-axetil, or cefpodoxime-proxetil) 2
  • Children over 3 years: Macrolides 2
  • Duration: 5-8 days 2

Skin and Soft Tissue Infections

• Impetigo:

  • First-line: Dicloxacillin, cefalexin, erythromycin, clindamycin, or amoxicillin-clavulanate 2

• Non-purulent skin infections:

  • First-line: Benzylpenicillin, phenoxymethylpenicillin, clindamycin, nafcillin, cefazolin, or cefalexin 2

• Purulent skin infections (likely Staphylococcus aureus):

  • First-line: (Dicl)oxacillin, cefazolin, clindamycin, cefalexin, doxycycline, or sulfamethoxazole-trimethoprim 2

• MRSA infections:

  • First-line: Vancomycin, linezolid, clindamycin, daptomycin, ceftaroline, doxycycline, or sulfamethoxazole-trimethoprim 2

Animal and Human Bites

• Animal bites:

  • First-line: Amoxicillin-clavulanate (oral) or ampicillin-sulbactam (IV) 2
  • Alternative options: Second/third-generation cephalosporins, doxycycline, or fluoroquinolones plus metronidazole for anaerobic coverage 2

• Human bites:

  • First-line: Amoxicillin-clavulanate or ampicillin-sulbactam 2
  • Alternative options: Carbapenems or doxycycline 2

Pathogen-Specific Antibiotic Selection

• Streptococcus pneumoniae (penicillin MIC <2):

  • First-line: Penicillin G, amoxicillin, amoxicillin-clavulanate, ampicillin, or ampicillin-sulbactam 2
  • Alternative: Cefuroxime, ceftriaxone, cefotaxime, levofloxacin, moxifloxacin, or doxycycline 2

• Methicillin-susceptible Staphylococcus aureus:

  • First-line: Oxacillin, cefazolin, or flucloxacillin 2
  • Alternative: Amoxicillin-clavulanate, levofloxacin, moxifloxacin, vancomycin, teicoplanin, or clindamycin 2

• Methicillin-resistant Staphylococcus aureus:

  • First-line: Vancomycin with rifampicin, teicoplanin with rifampicin, or linezolid 2

• Mycoplasma pneumoniae:

  • First-line: Doxycycline or minocycline 2
  • Alternative: Azithromycin, levofloxacin, or moxifloxacin 2

• Haemophilus influenzae:

  • Beta-lactamase negative: Amoxicillin 2
  • Beta-lactamase positive: Amoxicillin-clavulanate, cefuroxime, ceftriaxone, or other cephalosporins 2

Principles for Antibiotic Selection

• Prevention of antimicrobial resistance should be prioritized by selecting narrow-spectrum antibiotics when possible 2, 1
• Parsimony in antibiotic selection facilitates procurement and enhances access to key antibiotics required for common infections 2
• Benefits and harms should be considered, including clinical efficacy, time to symptom resolution, and potential side effects 2
• Feasibility factors include availability of appropriate formulations and options that facilitate transition from IV to oral therapy 2
• Complete the full course of antibiotic therapy as prescribed to prevent resistance development 3, 4

Important Considerations and Caveats

• Most Gram-positive infections can be treated with a small number of antibiotics (penicillin, cloxacillin, and erythromycin) 4
• For serious systemic infections, initial IV therapy may be appropriate, followed by oral antibiotics with high bioavailability after clinical improvement 5
• Bacterial eradication should be the goal of antimicrobial therapy to maximize clinical efficacy and reduce development of resistant organisms 6
• The duration of treatment should be the shortest that will reliably eradicate the pathogen(s) while being safe and well-tolerated 6
• Rapid diagnostics can help transition from empirical treatment with broad-spectrum antibiotics to more targeted therapy 7

Remember that antibiotic selection should be guided by local resistance patterns, and therapy may need to be adjusted based on culture and sensitivity results when available 2, 1.