What are the guidelines for choosing antibiotics for acute bacterial infections?

Guidelines for Choosing Antibiotics for Acute Bacterial Infections

Antibiotic selection should be pathogen-directed based on local resistance patterns whenever possible, with empiric therapy guided by the specific infection site, severity, and patient risk factors. 1

General Principles for Antibiotic Selection

• Choose antibiotics based on predicted effectiveness against likely pathogens, local resistance patterns, cost considerations, and potential side effects 1
• Avoid antibiotics for uncomplicated viral upper respiratory tract infections as this practice is inappropriate and strongly discouraged 1
• Use a pathogen-directed treatment approach whenever possible by obtaining appropriate cultures before initiating therapy 1
• Consider sequential intravenous-to-oral therapy when clinically appropriate to reduce hospitalization duration and costs 2, 3

Infection-Specific Antibiotic Selection

Urinary Tract Infections

Uncomplicated Pyelonephritis

• Oral therapy options:

  • Ciprofloxacin 500-750 mg twice daily for 7 days 1
  • Levofloxacin 750 mg daily for 5 days 1
  • Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days (if susceptibility confirmed) 1
  • Cefpodoxime 200 mg twice daily for 10 days 1
  • Ceftibuten 400 mg daily for 10 days 1

• Parenteral therapy options:

  • Ciprofloxacin 400 mg twice daily 1
  • Levofloxacin 750 mg daily 1
  • Ceftriaxone 1-2 g daily 1, 4
  • Cefotaxime 2 g three times daily 1
  • Aminoglycosides (gentamicin 5 mg/kg daily or amikacin 15 mg/kg daily) 1

Complicated UTIs

• Consider broader spectrum agents based on risk factors for multidrug-resistant organisms 1
• Reserve carbapenems and newer broad-spectrum agents for documented multidrug-resistant infections 1

Respiratory Tract Infections

Acute Bacterial Rhinosinusitis

• First-line options (mild disease, no recent antibiotic use):

  • Amoxicillin 1.5-4 g/day divided doses 1
  • Amoxicillin-clavulanate 875/125 mg twice daily or 500/125 mg three times daily 1, 5
  • Cefpodoxime, cefuroxime axetil, or cefdinir 1

• For β-lactam allergies:

  • Trimethoprim-sulfamethoxazole, doxycycline, macrolides (with caution due to 20-25% failure rates) 1

• For moderate disease or recent antibiotic use:

  • Respiratory fluoroquinolones (levofloxacin, moxifloxacin) 1
  • High-dose amoxicillin-clavulanate (4 g/250 mg per day) 1
  • Ceftriaxone (1-2 g/day for 5 days) 1

Pediatric Considerations

• For children with sinusitis, amoxicillin-clavulanate (90 mg/6.4 mg/kg/day) is recommended 1
• For respiratory infections in children under 3 years, 80-100 mg/kg/day of amoxicillin component in three divided doses 5

Skin and Soft Tissue Infections

• Consider coverage for both gram-positive and gram-negative organisms based on infection severity and risk factors 3, 4
• For complicated infections, combination therapy may be necessary to provide adequate coverage 3

Urethritis

• For gonococcal infection:

  • Ceftriaxone 1 g IM or IV single dose plus azithromycin 1 g oral single dose 1
  • Alternative: Cefixime 400 mg oral single dose plus azithromycin 1 g oral single dose 1

• For non-gonococcal infection:

  • Doxycycline 100 mg twice daily for 7 days 1
  • Alternative: Azithromycin 500 mg on day 1, then 250 mg for 4 days 1

Special Considerations

Antibiotic Resistance

• Consider local resistance patterns when selecting empiric therapy 1, 6
• Fluoroquinolones should only be used when resistance is <10% for the target pathogen 1
• Avoid widespread use of respiratory fluoroquinolones for milder disease to prevent resistance development 1

Treatment Duration

• Evaluate therapeutic efficacy after 72 hours of treatment 1, 5
• Consider alternative antibiotics or reevaluation if no improvement is observed after 72 hours 1, 5
• Complete the full course of therapy to prevent relapse and resistance development 7

Administration Considerations

• Amoxicillin-clavulanate should be taken with meals to reduce gastrointestinal upset 7
• For sequential therapy, transition from IV to oral when clinically appropriate (clinical improvement, ability to tolerate oral medications, functioning GI tract) 2, 3

Common Pitfalls to Avoid

• Overuse of broad-spectrum antibiotics: Reserve broad-spectrum agents for severe infections or documented resistance 1, 6
• Inadequate dosing: Ensure appropriate dosing based on infection site, severity, and patient factors 1
• Premature discontinuation: Complete the full course of therapy to prevent relapse and resistance 7
• Ignoring local resistance patterns: Base empiric therapy on local epidemiology 1, 8
• Treating viral infections with antibiotics: Antibiotics do not treat viral infections and inappropriate use contributes to resistance 1, 7