Is Pseudomonas sensitive to Moxifloxacin (a fluoroquinolone antibiotic)?

Pseudomonas Is Not Reliably Sensitive to Moxifloxacin

No, Pseudomonas aeruginosa is not reliably sensitive to moxifloxacin and should not be considered adequately covered by this antibiotic for empiric therapy. 1

Evidence of Pseudomonas Resistance to Moxifloxacin

• The American Academy of Ophthalmology's Bacterial Keratitis Preferred Practice Pattern (2019) specifically notes a sharp increase in resistance of Pseudomonas aeruginosa to moxifloxacin, from 19% in 2007 to 52% in 2009 in southern India 1
• A 20-year study in San Francisco found increasing overall resistance of organisms to moxifloxacin from 1996 to 2015, including Pseudomonas strains 1
• Fluoroquinolones are substrates for the multidrug efflux systems of Pseudomonas aeruginosa, which contributes to resistance patterns 2

Fluoroquinolone Selection for Pseudomonas Infections

When treating suspected Pseudomonas infections, the following algorithm should be used:

1. First-line options for Pseudomonas coverage:

   • Ciprofloxacin - specifically indicated for Pseudomonas infections including otitis externa 1
   • Levofloxacin - better activity against Pseudomonas than moxifloxacin 1

2. For severe Pseudomonas infections:

   • Combination therapy may be necessary (e.g., fortified antibiotics for keratitis) 1
   • Consider antipseudomonal beta-lactams (piperacillin-tazobactam, cefepime, carbapenems) for systemic infections 1

Clinical Implications

• Ocular infections: For Pseudomonas keratitis, ciprofloxacin 0.3%, ofloxacin 0.3%, and levofloxacin 1.5% are FDA-approved options 1
• Systemic infections: Moxifloxacin is not recommended for infections where Pseudomonas is a likely pathogen 1
• Otitis externa: Ciprofloxacin is specifically indicated for Pseudomonas-associated ear infections 1

Experimental Evidence

While some experimental studies have shown that moxifloxacin can reduce Pseudomonas CFU in rabbit models of keratitis 3, clinical guidelines still do not recommend moxifloxacin as a reliable agent for Pseudomonas infections due to increasing resistance patterns 1.

Common Pitfalls to Avoid

1. Don't assume all fluoroquinolones have equal activity against Pseudomonas:

   • Ciprofloxacin and levofloxacin have better antipseudomonal activity than moxifloxacin 1
   • Fourth-generation fluoroquinolones like moxifloxacin were designed primarily to improve gram-positive coverage 1

2. Don't rely on moxifloxacin for empiric coverage of Pseudomonas:

   • When Pseudomonas is suspected, choose ciprofloxacin or levofloxacin instead 1
   • For severe infections, consider combination therapy or alternative agents 1

3. Don't ignore local resistance patterns:

   • Resistance rates vary geographically and can be substantial (up to 52% in some regions) 1
   • Always consider local antibiogram data when available

In conclusion, while moxifloxacin may show some in vitro activity against certain Pseudomonas strains, the high and increasing rates of resistance make it an unreliable choice for empiric therapy when Pseudomonas is suspected or confirmed.