What are empirical antibiotics?

Empirical Antibiotics: Definition and Clinical Application

Empirical antibiotics are antimicrobial medications prescribed before a definitive causative pathogen is identified, based on the most likely infectious agents for a specific clinical syndrome, local resistance patterns, and patient risk factors. 1

Key Characteristics of Empirical Antibiotic Therapy

• Timing: Administered before microbiological confirmation (cultures, susceptibility testing)
• Purpose: To provide immediate coverage against the most likely pathogens while awaiting definitive diagnosis
• Basis: Selection guided by:
  • Clinical presentation and syndrome
  • Local epidemiology and resistance patterns
  • Patient risk factors for resistant organisms
  • Severity of illness

The AWaRe Classification System

The WHO categorizes antibiotics into three groups to guide appropriate use 1, 2:

1. Access (Green) - First-line options for common infections with lower resistance potential

   • Examples: amoxicillin, trimethoprim-sulfamethoxazole, doxycycline
   • Should be widely available, affordable, and of assured quality

2. Watch (Yellow) - Higher resistance potential but still recommended for specific indications

   • Examples: fluoroquinolones, carbapenems, macrolides
   • Target for stewardship monitoring programs

3. Reserve (Red) - Last-resort options for specific resistant infections

   • Used only when other alternatives are inadequate or have failed
   • Should be protected and prioritized in stewardship programs

When to Use Empirical Antibiotics

Empirical antibiotics are indicated in 1:

1. Severe infections with signs of sepsis - When delay in treatment could increase mortality
2. Specific high-risk populations:
   • Infants <3 months with suspected bacterial infection
   • Immunocompromised patients with severe illness
   • Patients with clinical features of sepsis and suspected enteric fever
3. Specific clinical scenarios:
   • Necrotizing fasciitis
   • Severe skin/soft tissue infections
   • Complicated intra-abdominal infections

When to Avoid Empirical Antibiotics

Empirical antibiotics should be avoided in 1:

1. Mild COVID-19 without evidence of bacterial superinfection
2. Immunocompetent patients with bloody diarrhea while awaiting test results (with exceptions)
3. Asymptomatic contacts of people with bloody diarrhea
4. STEC O157 infections and other Shiga toxin 2-producing E. coli
5. Clinically uninfected diabetic wounds

Principles of Empirical Antibiotic Selection

1. Start broad, then narrow: Initial broad coverage of likely pathogens, followed by de-escalation when culture results become available 1, 3
2. Consider local resistance patterns: Base selection on local surveillance and susceptibility data
3. Risk-stratify patients: Consider patient-specific risk factors for resistant organisms
4. Reassess regularly: Modify therapy when culture results become available (typically 2-4 days) 1
5. Balance individual and population health: Consider both patient outcomes and antimicrobial stewardship

Common Pitfalls in Empirical Antibiotic Use

1. Inadequate initial coverage: Associated with increased mortality, longer hospital stays, and higher costs 3
2. Failure to de-escalate: Continuing broad-spectrum therapy after pathogen identification increases resistance risk
3. Overuse in viral infections: Particularly problematic during the COVID-19 pandemic 1
4. Reliance on single biomarkers: Procalcitonin alone may be misleading in some COVID-19 patients 1
5. Ignoring local resistance patterns: Can lead to treatment failure

Best Practices for Empirical Antibiotic Use

1. Obtain cultures before starting antibiotics whenever possible
2. Document indication and planned duration at initiation
3. Reassess at 48-72 hours based on clinical response and culture results
4. De-escalate to narrower spectrum when possible 1, 3
5. Discontinue if infection is unlikely or confirmed to be viral
6. Follow local guidelines adapted to institutional resistance patterns

By following these principles, clinicians can optimize the use of empirical antibiotics to improve patient outcomes while minimizing antimicrobial resistance.