What is the appropriate empirical antibiotic therapy for adult patients with suspected bacterial infections in the Emergency Department (ED)?

Empirical Antibiotic Therapy in the Emergency Department

The appropriate empirical antibiotic therapy for adult patients with suspected bacterial infections in the Emergency Department should follow the "5Ds of stewardship": right diagnosis, drug, dose, duration, and de-escalation, with initial therapy guided by suspected infection site, severity, and local resistance patterns. 1

Initial Assessment and Decision Framework

1. Determine infection severity and likelihood:

   • Use clinical examination, vital signs, and laboratory markers (CRP, procalcitonin) to assess infection probability and severity
   • Obtain appropriate cultures BEFORE starting antibiotics whenever possible 1
   • Consider rapid diagnostic tests when available to guide therapy

2. Decision algorithm for initiating empiric antibiotics:

   • High severity (sepsis/septic shock): Start broad-spectrum antibiotics immediately after cultures 1
   • Moderate severity: Consider targeted therapy based on likely source
   • Low severity: Consider watchful waiting or delayed prescription when appropriate 1

Empiric Antibiotic Selection by Infection Site

Respiratory Infections

• Community-acquired pneumonia (moderate-severe):
  • First-line: Ceftriaxone 1-2g IV daily or Ampicillin-sulbactam 3g IV q6h
  • If Pseudomonas suspected: Cefepime 1-2g IV q8-12h 2
  • Add macrolide if atypical pathogens suspected

Intra-abdominal Infections

• Complicated intra-abdominal infections:
  • Cefepime 2g IV q8-12h plus metronidazole 500mg IV q8h 2
  • Alternative: Piperacillin-tazobactam 4.5g IV q6h

Urinary Tract Infections

• Uncomplicated/mild-moderate UTI:
  • Cefepime 0.5-1g IV q12h (7-10 days) 2
• Severe UTI/pyelonephritis:
  • Cefepime 2g IV q12h (10 days) 2

Skin and Soft Tissue Infections

• Uncomplicated:
  • Cefazolin 1-2g IV q8h
• Complicated/MRSA concern:
  • Vancomycin 15-20mg/kg IV q8-12h (target trough 15-20mg/mL) 3
  • Alternative: Linezolid 600mg IV/PO q12h 1, 3

Febrile Neutropenia

• Empiric therapy:
  • Cefepime 2g IV q8h as monotherapy 2
  • Consider adding vancomycin if line infection or gram-positive infection suspected

Special Considerations

MRSA Coverage

• Add MRSA coverage (vancomycin or linezolid) when:
  • Known MRSA colonization
  • Previous MRSA infection
  • High local MRSA prevalence
  • Severe skin/soft tissue infection with purulence
  • Severe pneumonia in areas with high MRSA rates 1

Pseudomonas Coverage

• Consider antipseudomonal coverage (cefepime, piperacillin-tazobactam) when:
  • Healthcare-associated infection
  • Recent hospitalization or antibiotic use
  • Structural lung disease (bronchiectasis, cystic fibrosis)
  • Immunocompromised state 1, 2

Immunocompromised Patients

• Lower threshold for empiric therapy
• Broader initial coverage often warranted
• Consider antifungal therapy in appropriate settings 1

De-escalation and Follow-up

1. Re-evaluate at 48-72 hours:

   • Review culture results
   • Assess clinical response
   • Narrow therapy based on culture results 1

2. Duration of therapy:

   • Uncomplicated UTI: 7-10 days
   • Pneumonia: 5-7 days (community-acquired), 7-14 days (hospital-acquired)
   • Skin/soft tissue: 5-10 days (uncomplicated), 7-14 days (complicated) 3

Common Pitfalls to Avoid

1. Overuse of broad-spectrum antibiotics: Recent research shows that while 65.1% of patients with suspected sepsis receive broad-spectrum antibiotics, resistant organisms are isolated in only 7.3% of cases 4

2. Failure to obtain cultures before antibiotics: This represents a missed opportunity to tailor therapy and de-escalate 1

3. Continuing empiric broad-spectrum therapy without de-escalation: Modify or discontinue antimicrobial treatment when a clinically plausible organism is identified 1

4. Treating colonization rather than infection: Distinguish between true infection and colonization to avoid unnecessary antibiotic use 5

5. Not considering local resistance patterns: Empiric therapy should be guided by local susceptibility patterns 1, 6

By following these principles, clinicians can provide appropriate empirical antibiotic therapy while practicing good antimicrobial stewardship in the emergency department setting.