Levofloxacin Susceptibility for Streptococcus pneumoniae
Levofloxacin is generally susceptible against Streptococcus pneumoniae infections, with resistance rates in the United States remaining below 2%, making it an effective treatment option for pneumococcal infections when clinically indicated. 1
Susceptibility Profile
- S. pneumoniae remains highly susceptible to levofloxacin in most regions, with overall resistance rates of 0.8% reported in the United States 1
- Levofloxacin has improved activity against S. pneumoniae compared to older fluoroquinolones like ciprofloxacin 2
- The FDA label for levofloxacin specifically indicates its effectiveness against both penicillin-susceptible and multi-drug resistant S. pneumoniae (MDRSP) 3
Regional Variation in Resistance
- While overall resistance rates remain low, there is significant geographic variation:
Clinical Efficacy
- Levofloxacin has demonstrated high clinical success rates (95-96%) against S. pneumoniae in community-acquired pneumonia trials 4, 2
- For multi-drug resistant S. pneumoniae (MDRSP), levofloxacin achieved 95% clinical and bacteriologic success 3
- Levofloxacin remains effective against macrolide-resistant S. pneumoniae, with clinical success rates of 96.3% 5
Dosing Considerations
- For community-acquired pneumonia:
- 500 mg once daily for 7-14 days, or
- 750 mg once daily for 5 days (shorter, high-dose regimen) 3
- Higher doses (750 mg) may help prevent resistance development by achieving higher drug concentrations 1
Resistance Concerns and Monitoring
Mechanism of Resistance
- Resistance occurs through stepwise mutations in:
- parC gene (encoding DNA topoisomerase IV)
- gyrA gene (encoding DNA gyrase) 1
- First-step mutations result in low-level resistance, while second-step mutations lead to higher resistance levels 1
Risk Factors for Resistance
- Prior fluoroquinolone exposure (especially multiple courses) 1, 6, 7
- Residence in long-term care facilities 1
- Geographic areas with known high resistance rates 1
Clinical Pitfalls and Recommendations
Monitor local resistance patterns: Resistance rates vary significantly by region; knowledge of local patterns is essential 1
Consider resistance testing: When S. pneumoniae is isolated, consider testing for fluoroquinolone susceptibility, especially in patients with risk factors for resistance 7
Avoid fluoroquinolone overuse: The IDSA guidelines express concern that misuse and overuse could lead to increased resistance and "the demise of fluoroquinolones as useful antibiotics" 1
Treatment failures: Clinical failures due to levofloxacin-resistant pneumococci have been reported, particularly in patients with prior fluoroquinolone exposure 6, 7
Alternative therapy: For patients with risk factors for resistance or in areas with high resistance rates, consider alternative agents such as β-lactams plus macrolides 1
Appropriate use: Reserve levofloxacin for patients with comorbidities or recent antibiotic use (within 3 months) rather than as first-line therapy in otherwise healthy individuals 1
In conclusion, while levofloxacin remains an effective agent against S. pneumoniae with overall low resistance rates, judicious use is necessary to preserve its efficacy. Local resistance patterns should guide therapy decisions, and alternative agents should be considered in patients with risk factors for fluoroquinolone-resistant S. pneumoniae.