What cephalosporin (a type of antibiotic) is effective against Pseudomonas aeruginosa?

Cephalosporins with Pseudomonas Coverage

The cephalosporins that cover Pseudomonas aeruginosa are ceftazidime (third-generation), cefoperazone (third-generation), and cefepime (fourth-generation), with ceftazidime and cefepime being the most widely used and recommended options. 1, 2

Primary Anti-Pseudomonal Cephalosporins

Ceftazidime (Third-Generation)

• FDA-approved specifically for Pseudomonas aeruginosa infections including lower respiratory tract infections, skin/soft tissue infections, urinary tract infections, bacteremia, bone/joint infections, and CNS infections 2
• Demonstrates excellent in vitro activity with mean MIC <2 mg/L against clinical P. aeruginosa isolates, with >90% of strains inhibited at concentrations ≤8 mg/L 3, 4
• Recommended dosing: 2 grams IV every 8 hours for Pseudomonas infections 5
• More active against Pseudomonas than other third-generation cephalosporins (cefotaxime, ceftriaxone) which lack anti-pseudomonal activity 1

Cefepime (Fourth-Generation)

• Possesses similar anti-Pseudomonas activity to ceftazidime while offering broader spectrum coverage against Gram-positive cocci and AmpC-producing organisms 1, 6, 7
• Recommended dosing: 2 grams IV every 12 hours for moderate-to-severe Pseudomonas infections 6
• Maintains activity when serum levels exceed MIC for 60-70% of the dosing interval 6
• Must be combined with metronidazole for empiric therapy as it lacks anaerobic coverage 1

Cefoperazone (Third-Generation)

• Third-generation cephalosporin with documented anti-Pseudomonas activity 1
• Less commonly used than ceftazidime or cefepime in current practice 1

Clinical Application Algorithm

For empiric therapy when Pseudomonas is suspected:

1. Severe infections or ICU patients: Use cefepime 2g IV q12h OR ceftazidime 2g IV q8h, combined with either ciprofloxacin, an aminoglycoside, or vancomycin (if MRSA concern) 1
2. Moderate infections with confirmed susceptibility: Ceftazidime or cefepime monotherapy is acceptable 1
3. Diabetic foot infections: Piperacillin-tazobactam preferred over cephalosporins for Pseudomonas coverage 1

Critical Caveats

Resistance patterns matter: Recent outbreaks have identified P. aeruginosa strains that are cefepime-resistant but ceftazidime-susceptible due to MexXY-OprM efflux pump overexpression combined with PSE-1 β-lactamase production 8. This discordant susceptibility pattern emphasizes the importance of:

• Always obtaining culture and susceptibility data 2
• Considering local antibiogram patterns 1
• Using combination therapy for severe infections until susceptibilities are known 1

Monotherapy limitations: Cephalosporin monotherapy for Pseudomonas should be reserved for mild-to-moderate infections in immunocompetent patients with confirmed susceptibility 1. For severe infections, sepsis, or nosocomial pneumonia, combination therapy with an aminoglycoside or fluoroquinolone is strongly recommended 1.

Duration: Treatment courses of 10-14 days are recommended for complicated infections caused by P. aeruginosa, with the full 14-day course preferred in elderly patients or recurrent infections 5