Is Bordetella pertussis sensitive to quinolones?

Bordetella pertussis Sensitivity to Quinolones

Direct Answer

Despite demonstrating in vitro activity against Bordetella pertussis, quinolones should NOT be used for treatment or prophylaxis of pertussis because clinical effectiveness has never been established. 1

The Critical Distinction: In Vitro vs. Clinical Efficacy

Laboratory Sensitivity Does Not Equal Clinical Effectiveness

• B. pertussis demonstrates susceptibility to quinolones in laboratory testing, with studies showing MICs ranging from ≤0.008 mg/L for gemifloxacin to 0.015 mg/L for ciprofloxacin 2
• Finnish isolates tested between 2006-2017 showed inhibition zones of 22-27mm diameter for nalidixic acid, indicating phenotypic susceptibility 3
• However, the CDC explicitly states that this in vitro activity does not predict clinical effectiveness for pertussis treatment 1

Why Quinolones Fail Clinically Despite Laboratory Activity

• No published studies demonstrate that fluoroquinolones successfully eradicate B. pertussis from the nasopharynx in actual patients 1
• Quinolones may have inadequate penetration into respiratory secretions where B. pertussis colonizes, despite achieving adequate serum levels 1
• The organism's location in respiratory epithelial tissue may not be reached by achievable quinolone concentrations at the site of infection 1

Recommended Treatment Options

First-Line Therapy: Macrolides

• Azithromycin is the preferred first-line agent for all age groups, with dosing of 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) on days 2-5 for children ≥6 months, and 500 mg day 1 followed by 250 mg days 2-5 for adults 4
• Macrolides rapidly clear B. pertussis from the nasopharynx when administered early (catarrhal phase, first 2 weeks) and decrease coughing paroxysms 4
• Erythromycin and clarithromycin are equally effective alternatives, though erythromycin should be avoided in infants <6 months due to infantile hypertrophic pyloric stenosis risk 4

Second-Line Therapy: Trimethoprim-Sulfamethoxazole

• TMP-SMZ is the ONLY alternative to macrolides with proven clinical effectiveness for eradicating B. pertussis from the nasopharynx 1
• Use TMP-SMZ in patients who cannot tolerate macrolides or have macrolide-resistant B. pertussis 1
• Contraindicated in infants <2 months, pregnant women, and nursing mothers due to kernicterus risk 1

Clinical Pitfalls to Avoid

Common Mistake: Using Quinolones Based on Susceptibility Reports

• Laboratory reports may show quinolone susceptibility, but this should not guide clinical decision-making for pertussis 1
• Quinolones have potentially harmful side effects in pediatric populations, making them particularly problematic since pertussis commonly affects infants and children 1

Treatment Timing Considerations

• Start antibiotics immediately upon clinical suspicion without waiting for culture confirmation 4
• Early treatment (first 2 weeks) provides maximal clinical benefit; late treatment (>3 weeks) has limited symptom benefit but remains indicated to prevent transmission 4
• Isolate patients for 5 days after starting appropriate antibiotics (macrolides or TMP-SMZ, NOT quinolones) 4

Emerging Resistance Patterns

• Macrolide resistance exists but remains relatively uncommon in most regions, with one study showing 62.4% high-level resistance in certain Chinese populations 5
• When macrolide resistance is confirmed, β-lactams (piperacillin, cefoperazone-sulbactam, meropenem) show better clearance rates than macrolides at 14 days post-treatment 5
• Even in macrolide-resistant cases, quinolones remain inappropriate due to lack of proven clinical efficacy 1