Does Cortisporin (neomycin and polymyxin B) otic drops effectively treat methicillin-resistant Staphylococcus aureus (MRSA) infections of the ear?

Cortisporin Otic Drops for MRSA Ear Infections

Cortisporin (neomycin/polymyxin B) otic drops should NOT be relied upon as monotherapy for MRSA ear infections, as resistance to these topical agents has increased significantly, and systemic anti-MRSA therapy with oral TMP-SMX or clindamycin is required for effective treatment. 1, 2

Evidence of Declining Efficacy Against MRSA

• Neomycin and polymyxin B susceptibility has declined markedly, with mean MICs for major ear pathogens (including S. aureus) rising above the breakpoint for polymyxin B (≥4 μg/mL) in studies from 1999-2000 compared to 1995-1996. 2

• In a pediatric case series of CA-MRSA otitis media with otorrhea, all MRSA isolates were resistant to fluoroquinolones (levofloxacin), and 2 of 6 were resistant to clindamycin, but all were sensitive to gentamicin and polymyxin B-containing topical drops. 1

• However, these patients required combination therapy with both systemic TMP-SMX AND topical agents (gentamicin or Cortisporin) to achieve clinical resolution—topical therapy alone was insufficient. 1

Recommended Treatment Approach for MRSA Otitis

When MRSA is Suspected or Confirmed:

• Obtain cultures from persistent or nonresponsive otorrhea to identify MRSA and determine antibiotic sensitivities. 1

• Initiate systemic anti-MRSA therapy as the primary treatment:

  • TMP-SMX (1-2 double-strength tablets twice daily in adults; 8-12 mg/kg/day in 2 divided doses in children) is the preferred first-line systemic agent. 3, 1
  • Clindamycin (300-450 mg three times daily in adults; 10-13 mg/kg/dose every 6-8 hours in children) is an alternative if local resistance is <10%. 3, 4

• Add topical therapy as adjunctive treatment only:

  • Cortisporin drops may be used as an adjunct to systemic therapy, but should not be used alone. 1
  • Consider gentamicin-containing drops as an alternative topical agent. 1

Treatment Duration:

• 5-10 days of systemic antibiotic therapy is recommended for uncomplicated otitis with adequate drainage. 3, 5

Critical Pitfalls to Avoid

• Never use Cortisporin drops as monotherapy for suspected MRSA otitis—all successfully treated cases in the literature required systemic antibiotics. 1

• Do not assume fluoroquinolone otic drops will be effective—MRSA isolates from otitis are frequently fluoroquinolone-resistant. 1

• Avoid empirical clindamycin if local MRSA resistance exceeds 10%—verify local resistance patterns before selecting this agent. 4

• Beta-lactam antibiotics (amoxicillin-clavulanate, cephalosporins) provide no MRSA coverage and should not be used empirically when MRSA is suspected. 3, 1