Is Pseudomonas (Ps.) aeruginosa susceptible to cefepime?

Pseudomonas aeruginosa Susceptibility to Cefepime

Yes, Pseudomonas aeruginosa is susceptible to cefepime, which is specifically indicated for P. aeruginosa infections according to FDA labeling, though susceptibility patterns vary and resistance can develop.

Evidence for Susceptibility

The FDA drug label for cefepime explicitly states that it is indicated for pneumonia caused by Pseudomonas aeruginosa, as well as complicated intra-abdominal infections (used in combination with metronidazole) caused by P. aeruginosa 1. This official indication confirms that P. aeruginosa is considered a susceptible organism to cefepime.

Additionally, the Infectious Diseases Society of America (IDSA) guidelines recommend cefepime as an appropriate monotherapy option for high-risk patients with febrile neutropenia, with coverage of P. aeruginosa being an essential component of the initial empirical antibiotic regimen 2.

Clinical Applications

Cefepime is recommended in several clinical scenarios involving P. aeruginosa:

• Febrile neutropenia: Cefepime is recommended as monotherapy for empirical treatment in high-risk patients 2
• Pneumonia: For moderate to severe pneumonia caused by P. aeruginosa 1
• Hospital-acquired pneumonia (HAP)/ventilator-associated pneumonia (VAP): Cefepime is recommended as an antipseudomonal cephalosporin for empiric treatment when P. aeruginosa is suspected 3
• Intra-abdominal infections: Cefepime (in combination with metronidazole) is recommended for complicated intra-abdominal infections with suspected P. aeruginosa 3, 1

Dosing Considerations

For P. aeruginosa infections, higher doses of cefepime are typically recommended:

• 2g IV every 8 hours for P. aeruginosa pneumonia 1
• The pharmacodynamic target for efficacy against P. aeruginosa is maintaining serum levels above the MIC for 60-70% of the dosing interval 4

Resistance Considerations

While P. aeruginosa is generally susceptible to cefepime, several important caveats should be noted:

1. Resistance development: P. aeruginosa can develop resistance to cefepime, though research suggests this occurs more slowly compared to other cephalosporins 5

2. Variable susceptibility: Studies have shown varying susceptibility rates. One study in cystic fibrosis patients found 16.4% of P. aeruginosa isolates were non-susceptible to cefepime 6

3. Risk of treatment failure: For patients with risk factors for P. aeruginosa infection who don't respond to initial therapy, consideration should be given to resistant strains 2

4. Combination therapy: For severe infections, particularly in immunocompromised patients, combination therapy (cefepime plus an aminoglycoside or fluoroquinolone) may be considered to enhance efficacy and prevent resistance development 3

Practical Approach

When treating suspected P. aeruginosa infections:

1. Obtain appropriate cultures before initiating antibiotics when possible
2. Use appropriate dosing (2g IV every 8 hours for P. aeruginosa)
3. Monitor clinical response
4. Consider combination therapy for severe infections or in immunocompromised patients
5. Be vigilant for development of resistance, especially with prolonged therapy

In summary, while cefepime is active against P. aeruginosa and is FDA-approved for treating P. aeruginosa infections, susceptibility should be confirmed by culture and susceptibility testing whenever possible due to the potential for resistance development.