What are the antibiotics of choice for treating infections?

Antibiotics of Choice for Treating Infections

The antibiotics of choice for treating infections should be selected based on the type and severity of infection, with amoxicillin-clavulanic acid being the first-line treatment for mild to moderate infections and ceftriaxone/cefotaxime plus metronidazole or piperacillin-tazobactam for severe infections. 1

Selection Algorithm Based on Infection Type and Severity

Mild to Moderate Infections

• First-line options:

  • Amoxicillin-clavulanic acid (Access category) 1, 2
  • For skin/soft tissue infections: Cloxacillin or cefalexin 1
  • For children with polymicrobial infections: Ampicillin + gentamicin + metronidazole 1, 2

• Second-line options:

  • Ciprofloxacin (Watch category) + metronidazole (Access category) 1
  • Cefotaxime or ceftriaxone (Watch category) + metronidazole (Access category) 1

Severe Infections

• First-line options:

  • Cefotaxime or ceftriaxone (Watch category) + metronidazole (Access category) 1
  • Piperacillin-tazobactam (Watch category) 1, 2

• Second-line options:

  • Ampicillin + gentamicin + metronidazole 1
  • Meropenem (Watch category) - reserved for severe infections with resistant organisms 1, 2

Special Situations

Necrotizing Fasciitis

• Clindamycin + piperacillin-tazobactam (with or without vancomycin) 1
• Ceftriaxone + metronidazole (with or without vancomycin) 1

MRSA Suspected or Confirmed

• Vancomycin (15-20 mg/kg IV every 8-12 hours) 2
• Linezolid (600 mg PO/IV twice daily) 2
• Clindamycin (300-450 mg orally four times daily) 2
• Sulfamethoxazole-trimethoprim (1-2 double-strength tablets twice daily) 2

Administration Guidelines

Amoxicillin-Clavulanate

• May be taken every 8 hours or every 12 hours depending on dose prescribed 3
• Each dose should be taken with a meal or snack to reduce gastrointestinal upset 3
• For 875/125 mg formulation: administered every 12 hours (equivalent efficacy to 500/125 mg every 8 hours with fewer gastrointestinal side effects) 4

Treatment Duration

• Intra-abdominal infections: 7-14 days 2
• Uncomplicated skin and soft tissue infections: 5-10 days 2
• Complicated skin and soft tissue infections: 7-14 days 2
• Osteomyelitis: Minimum 8 weeks 2

Monitoring and Assessment

• Assess clinical response within 72 hours of initiating therapy 2
• Consider changing antibiotic regimen, obtaining cultures, or surgical intervention if no improvement is seen 2
• For wounds, regular assessments should be performed with consideration of additional debridement if needed 2

Critical Considerations and Pitfalls

Resistance Concerns

• The WHO guidelines prioritize antibiotics with narrower spectrum of activity to prevent emergence and spread of resistance 1
• Fluoroquinolone and carbapenem-sparing approaches are recommended when appropriate alternatives exist 1
• Cefepime was excluded from recommendations due to concerns about increased mortality 1

Common Prescribing Errors

1. Overuse of broad-spectrum agents: Using amoxicillin-clavulanate when amoxicillin alone would suffice may select for resistance in gram-negative pathogens 5, 6
2. Inadequate dosing: Underdosing antibiotics can lead to treatment failure and promote resistance 3
3. Premature discontinuation: Not completing the full course of therapy decreases effectiveness and increases likelihood of resistance development 3
4. Failure to adjust for severe infections: Not escalating to appropriate broad-spectrum coverage for severe infections can lead to treatment failure 1
5. Inadequate source control: Antibiotics alone may be insufficient without proper debridement or drainage of infected collections 2

Patient Education

• Antibiotics should only be used to treat bacterial infections, not viral infections 3
• Complete the full course of therapy even if feeling better 3
• Monitor for diarrhea, especially severe or bloody diarrhea, which may indicate C. difficile infection 3
• Amoxicillin-clavulanate contains a penicillin-class drug that can cause allergic reactions 3

By following these evidence-based recommendations for antibiotic selection based on infection type and severity, clinicians can optimize treatment outcomes while minimizing the risk of antimicrobial resistance and adverse effects.