Is cefdinir (Omnicef) effective against Klebsiella pneumoniae (K. pneumoniae) infections?

Cefdinir Does Not Adequately Cover Klebsiella Enterobacter

Cefdinir (Omnicef) is not recommended for the treatment of Klebsiella pneumoniae infections, particularly carbapenem-resistant strains, as it lacks sufficient activity against these organisms. 1 The FDA drug label explicitly states that while cefdinir exhibits some in vitro activity against Klebsiella pneumoniae, its safety and effectiveness in treating clinical infections due to this organism have not been established in adequate and well-controlled clinical trials.

Spectrum of Activity of Cefdinir

Cefdinir is an oral third-generation cephalosporin with the following characteristics:

• FDA-approved indications: Community-acquired respiratory tract infections and uncomplicated skin infections 1

• Documented activity against:

  • Staphylococcus aureus (methicillin-susceptible strains only)
  • Streptococcus pneumoniae (penicillin-susceptible strains only)
  • Streptococcus pyogenes
  • Haemophilus influenzae
  • Haemophilus parainfluenzae
  • Moraxella catarrhalis 1

• Limited activity against Enterobacteriaceae: While cefdinir shows some in vitro activity against certain Enterobacteriaceae, including Klebsiella pneumoniae, this activity is insufficient for reliable clinical use against these pathogens 1, 2

Preferred Treatments for Klebsiella Infections

For Klebsiella pneumoniae infections, particularly carbapenem-resistant strains, the following treatments are recommended:

• First-line therapy: Ceftazidime-avibactam 2.5g IV every 8 hours 3
• Alternative options:
  • Meropenem-vaborbactam 4g IV q8h
  • Imipenem-cilastatin-relebactam 1.25g IV q6h
  • For complicated UTIs: plazomicin 15 mg/kg IV q12h 3

Clinical Considerations

1. Resistance mechanisms: Klebsiella pneumoniae often produces beta-lactamases that can hydrolyze cefdinir. While cefdinir is stable to some beta-lactamases, it is not effective against many of the enzymes produced by Enterobacteriaceae 1, 2

2. Carbapenem-resistant strains: For carbapenem-resistant Klebsiella (CRE), newer agents are required:

   • Ceftazidime-avibactam is recommended as first-line therapy 3
   • For metallo-beta-lactamase (MBL) producing strains, ceftazidime-avibactam plus aztreonam or cefiderocol may be used 4

3. Treatment duration: For Klebsiella infections, treatment duration varies by site:

   • Bloodstream infections: 10-14 days
   • Complicated UTIs: 7-14 days
   • Pneumonia: 7-14 days 3

Pitfalls to Avoid

• Do not use cefdinir for serious Klebsiella infections: Despite some in vitro activity, clinical efficacy has not been established 1

• Avoid third-generation cephalosporins for CRE: They may induce AmpC β-lactamase production, leading to increased resistance 3

• Consider infectious disease consultation: Highly recommended for management of CRE infections 3

• Dosing adjustments: Required in patients with renal impairment (CrCl <30 mL/min) 1

In summary, while cefdinir may show some in vitro activity against certain strains of Klebsiella pneumoniae, it is not recommended for clinical use against these pathogens, especially for serious or resistant infections. More potent agents with established clinical efficacy should be used instead.