Should I start Antibiotics (ABX)?

When to Start Antibiotics: Evidence-Based Approach

Antibiotics should be initiated as soon as the clinical diagnosis of an infection requiring antimicrobial therapy is established, particularly for sepsis, septic shock, and acute bacterial rhinosinusitis (ABRS). 1

Decision Algorithm for Starting Antibiotics

Immediate Antibiotic Initiation (Start Now)

• Sepsis or septic shock: Administer IV antimicrobials within one hour of recognition 1
• Acute Bacterial Rhinosinusitis (ABRS): Start when clinical diagnosis is established 1
• Complicated intra-abdominal infections: Begin antibiotics as soon as possible 1
• Post-operative peritonitis: Immediate initiation required 1

Delayed or No Antibiotics (Don't Start)

• Uncomplicated intra-abdominal infections with adequate source control (e.g., uncomplicated appendicitis, cholecystitis) 1
• Viral upper respiratory infections without bacterial superinfection 1
• Bacterascites without symptoms (often self-resolves) 2

Clinical Criteria for Diagnosing Infections Requiring Antibiotics

ABRS Diagnostic Criteria

• Purulent nasal drainage for up to 4 weeks PLUS
• Nasal obstruction, facial pain/pressure/fullness, or both 1
• Worsening after initial improvement ("double sickening") strongly suggests bacterial infection 1

Sepsis Criteria

• Suspected infection with organ dysfunction
• Elevated lactate levels as marker of tissue hypoperfusion 1

Antibiotic Selection Principles

1. Cover likely pathogens based on infection site:

   • Intra-abdominal: Cover enteric gram-negative aerobic and facultative bacilli and β-lactam-susceptible gram-positive cocci 1
   • ABRS: Amoxicillin-clavulanate is recommended over amoxicillin alone 1

2. Consider local resistance patterns and risk factors for resistant organisms:

   • Healthcare-associated infections require broader coverage 1, 2
   • Prior antibiotic use increases risk for resistant organisms 1

3. Obtain appropriate cultures before starting antibiotics when possible:

   • Blood cultures (at least two sets)
   • Site-specific cultures (e.g., paracentesis for ascites) 2
   • Do not delay antibiotics >45 minutes to obtain cultures in critically ill patients 1

Duration of Therapy

• ABRS: 5-7 days for adults; 10-14 days for children 1
• Complicated intra-abdominal infections with adequate source control: 3-5 days 1
• Spontaneous bacterial peritonitis: 5-7 days 2

Monitoring and De-escalation

• Reassess antibiotic therapy daily for potential de-escalation 1
• For ABRS, assess treatment failure if no improvement after 7 days 1
• For intra-abdominal infections, ongoing signs of peritonitis beyond 5-7 days warrant diagnostic investigation 1

Common Pitfalls to Avoid

1. Delaying antibiotics in sepsis or septic shock - associated with increased mortality 1
2. Treating viral upper respiratory infections with antibiotics - contributes to antimicrobial resistance 1
3. Continuing antibiotics unnecessarily after adequate source control in uncomplicated intra-abdominal infections 1
4. Using inadequate dosing in critically ill patients - altered pharmacokinetics may require higher loading doses of hydrophilic antimicrobials 1
5. Failing to narrow spectrum once pathogen identification and sensitivities are established 1

Remember that the decision to start antibiotics should balance the benefits of early appropriate therapy against the risks of antimicrobial resistance. When infection requiring antibiotics is diagnosed, prompt initiation is crucial for optimal outcomes, particularly in critically ill patients.