Levaquin Coverage of Gram-Negative Rods
Yes, Levaquin (levofloxacin) provides excellent coverage against most Gram-negative rods, with susceptibility rates exceeding 85% for common Enterobacteriaceae and documented activity against key respiratory and urinary pathogens. 1, 2
Spectrum of Activity Against Gram-Negative Rods
Levofloxacin demonstrates broad-spectrum activity against Gram-negative bacteria through inhibition of bacterial topoisomerase IV and DNA gyrase 2. The FDA-approved labeling specifically lists the following Gram-negative rods as covered organisms 2:
Enterobacteriaceae (Excellent Coverage):
- Escherichia coli - MIC₅₀ and MIC₉₀ <0.5 mg/L, susceptibility >85% 1, 3
- Klebsiella pneumoniae - susceptibility >85% 1, 3
- Enterobacter cloacae - susceptibility >85% 2, 3
- Enterobacter aerogenes - susceptibility >85% 3
- Proteus mirabilis 2
- Serratia marcescens - susceptibility approximately 80% 2, 3
- Citrobacter species - susceptibility >85% 3
Respiratory Pathogens (Excellent Coverage):
Other Gram-Negative Rods:
- Pseudomonas aeruginosa - listed as covered but with significant resistance concerns (MIC₉₀ >32 mg/L, susceptibility <65%) 2, 3
- Acinetobacter species - susceptibility approximately 80% 3
Clinical Efficacy Data
Urinary Tract Infections: Levofloxacin achieves clinical success rates of 92-93.3% and bacteriological eradication rates of 93.6-94.7% in complicated UTIs caused by Gram-negative rods 4. The drug is specifically indicated for UTIs caused by E. coli, Pseudomonas aeruginosa, Enterobacter species, Citrobacter species, and Serratia species 1.
Respiratory Tract Infections: In community-acquired pneumonia, levofloxacin demonstrates clinical success rates of 87-96% and bacteriological eradication rates of 87-100% against Gram-negative respiratory pathogens 4, 5. For hospital-acquired and ventilator-associated pneumonia, levofloxacin 750 mg IV daily is listed as an appropriate empiric agent for Gram-negative coverage 1.
Intra-Abdominal Infections: Moxifloxacin (a related fluoroquinolone) shows >85% susceptibility against Enterobacteriaceae in Taiwan, with levofloxacin demonstrating similar activity patterns 1. Community-acquired E. coli and K. pneumoniae isolates show 50-60% susceptibility even among ESBL-producing strains 1.
Important Resistance Considerations
Pseudomonas aeruginosa: This organism demonstrates significant resistance to levofloxacin with MIC₉₀ values >32 mg/L and susceptibility rates <65% 3. When P. aeruginosa is suspected, dual antipseudomonal coverage is recommended rather than relying on levofloxacin monotherapy 1.
Acinetobacter species: Susceptibility rates are approximately 80%, which is lower than for Enterobacteriaceae 3. For severe infections with Acinetobacter, alternative agents should be considered 1.
ESBL-Producing Organisms: While levofloxacin retains some activity (50-60% susceptibility) against ESBL-producing E. coli and K. pneumoniae, carbapenems are preferred for documented ESBL infections 1.
Resistance Trends: Fluoroquinolone resistance in pediatric Gram-negative isolates has remained below 5% overall, with E. coli resistance rates of 4-7% in recent surveillance data 1. However, resistance is expected to increase with expanded use 1.
Dosing for Gram-Negative Coverage
Standard dosing: 500 mg once daily for most infections 2, 4
High-dose regimen: 750 mg once daily for nosocomial pneumonia and severe infections 1, 6
Renal adjustment required: Clearance is substantially reduced in patients with creatinine clearance <50 mL/min, necessitating dose reduction 2, 7
Clinical Caveats
Avoid in documented Pseudomonas infections as monotherapy - use combination therapy with an antipseudomonal beta-lactam instead 1.
Not first-line for ESBL producers - carbapenems or newer beta-lactam/beta-lactamase inhibitor combinations are preferred 1, 8.
Drug interactions: Separate administration from aluminum/magnesium antacids and ferrous sulfate by at least 2 hours to avoid decreased absorption 2, 7.
Bioavailability: Oral absorption approaches 100%, allowing seamless IV-to-oral conversion without dose adjustment 2, 7.