When should antibiotics be prescribed and what are the guidelines for their use?

When to Prescribe Antibiotics: Evidence-Based Guidelines

Antibiotics should NOT be prescribed routinely for most respiratory infections or suspected infections without clear clinical justification—prescribe only when bacterial infection is documented or highly likely based on specific clinical criteria, severity markers, and microbiological evidence. 1

General Principles for Antibiotic Prescribing

Do NOT Prescribe Antibiotics For:

• COVID-19 patients without clinical justification (bacterial coinfection occurs in only 5.1% of cases) 1
• Nonspecific upper respiratory tract infections in immunocompetent adults (typically viral) 2
• Acute rhinosinusitis within the first 5 days (viral window period) 1
• Simple chronic bronchitis exacerbations even with fever present 1
• Purulent nasal secretions alone (presence of neutrophils does not indicate bacterial infection) 1, 2

DO Prescribe Antibiotics When:

Severity-Based Criteria:

• Severe illness presentation with systemic toxicity, sepsis, or septic shock 1
• Critically ill patients requiring ICU admission or mechanical ventilation 1
• Persistent fever >38°C for >3 days despite symptomatic treatment 1

Syndrome-Specific Criteria:

• Acute bacterial rhinosinusitis: Symptoms persisting >10 days without improvement OR worsening after initial improvement 1
• COPD exacerbations: At least 2 of 3 Anthonisen criteria (increased dyspnea, sputum volume, sputum purulence) 1
• Community-acquired pneumonia: Clinical and radiographic evidence of lower respiratory infection 1
• Uncomplicated cystitis: Documented UTI symptoms 1
• Cellulitis: Clinical diagnosis of bacterial skin infection 1

Pre-Treatment Requirements

Before prescribing empirical antibiotics, obtain: 1

• Blood cultures (for hospitalized/critically ill patients)
• Sputum cultures or respiratory specimens
• Urinalysis and urine culture (for suspected UTI)
• Site-specific cultures when feasible

This comprehensive microbiologic workup facilitates antibiotic adjustment, de-escalation, or discontinuation based on results. 1

Risk Stratification for Antibiotic Selection

Assess Risk Factors for Multidrug-Resistant Organisms (MDROs):

Pseudomonas aeruginosa risk (requires ≥2 factors): 1

• Recent hospitalization
• Frequent antibiotic use (>4 courses/year or within last 3 months)
• Severe COPD (FEV1 <30%)
• Oral corticosteroids (>10mg prednisolone daily for 2 weeks)

MRSA risk factors: 1, 3

• Prior MRSA infection or colonization
• Injection drug use
• Recent healthcare exposure

Antibiotic Selection Framework

Use WHO AWaRe Classification: 4

Access Group (First-Line):

• Narrow-spectrum agents with lower resistance potential
• Examples: amoxicillin, ampicillin, benzylpenicillin, gentamicin, cloxacillin
• Preferred for empiric treatment of common infections

Watch Group (Second-Line):

• Reserve for specific indications or documented resistance
• Examples: fluoroquinolones, carbapenems, third-generation cephalosporins
• Higher toxicity and resistance concerns

Reserve Group:

• Only when other alternatives fail or multidrug resistance documented
• Protected for stewardship programs

Condition-Specific Recommendations

COPD Exacerbations:

Simple chronic bronchitis: No immediate antibiotics; reassess at 2-3 days 1

Chronic obstructive bronchitis (FEV1 35-80%):

• Prescribe if ≥2 Anthonisen criteria present 1
• First-line: amoxicillin, first-generation cephalosporins, macrolides 1

Severe COPD (FEV1 <35%) or respiratory insufficiency:

• Immediate antibiotics recommended 1
• Second-line: amoxicillin-clavulanate, cefuroxime-axetil, levofloxacin, moxifloxacin 1
• Add antipseudomonal coverage (ciprofloxacin) if risk factors present 1

Community-Acquired Pneumonia:

Duration: 5 days for clinically stable patients (afebrile for 48-72 hours, normal vital signs, able to eat, normal mentation) 1

Urinary Tract Infections:

Uncomplicated cystitis: 1

• Nitrofurantoin 5 days
• TMP-SMZ 3 days
• Fosfomycin single dose

Uncomplicated pyelonephritis: 1

• Fluoroquinolones 5-7 days
• TMP-SMZ 14 days (based on susceptibility)

Cellulitis:

Nonpurulent cellulitis: 5-6 days of antibiotics active against streptococci (requires close self-monitoring and follow-up) 1

Acute Rhinosinusitis:

Watchful waiting for first 5 days (viral window) 1

Moderate cases: Intranasal corticosteroids first; add antibiotics only if no improvement after 14 days 1

Severe cases: Combination intranasal corticosteroids plus antibiotics 1

Biomarkers and Laboratory Data

Elevated inflammatory markers may suggest bacterial infection but should NOT be used alone to initiate antibiotics: 1

• Higher WBC counts
• Elevated CRP
• Procalcitonin >0.5 ng/mL

These markers are most useful in critically ill patients but require clinical correlation. 1

Common Pitfalls to Avoid

• Over-prescribing for viral infections: 81-92% of acute rhinosinusitis cases receive antibiotics despite only 0.5-2% having bacterial etiology 1
• Prolonged duration: Default 10-day courses are often unnecessary; shorter courses reduce resistance and adverse events 1
• Ignoring local resistance patterns: Empiric choices must account for regional antibiotic susceptibility 1, 5
• Prescribing without cultures: Obtain specimens before starting antibiotics to enable de-escalation 1
• Using mucus color as indication: Purulent secretions reflect neutrophils, not bacteria 1, 2

Antibiotic Stewardship Principles

Reassess at 48-72 hours: 1

• Review culture results
• De-escalate to narrow-spectrum agents when possible
• Discontinue if bacterial infection ruled out
• Switch IV to oral when clinically stable

Avoid routine prophylaxis: Do not prescribe antibiotics for prevention in chronic bronchitis/COPD 1

Document clinical justification: Patients receiving antibiotics with clear clinical indications have lower mortality, higher discharge rates, and shorter hospital stays compared to those receiving antibiotics without justification 1