From the FDA Drug Label
Cephalexin has no activity against Pseudomonasspp., or Acinetobacter calcoaceticus.
The FDA drug label does not provide information about the effectiveness of amoxiclav against Pseudomonas aeruginosa. Keflex (cephalexin) does not cover Pseudomonas aeruginosa. Amoxiclav is not mentioned in the provided drug label, therefore its effectiveness against Pseudomonas aeruginosa cannot be determined from this information 1.
From the Research
Neither Keflex (cephalexin) nor amoxiclav (amoxicillin-clavulanic acid) effectively covers Pseudomonas aeruginosa infections. These antibiotics lack sufficient activity against this gram-negative bacterium, which is naturally resistant to many common antibiotics. Pseudomonas aeruginosa requires specific anti-pseudomonal antibiotics such as ceftazidime, piperacillin-tazobactam, ciprofloxacin, or carbapenems like meropenem, as shown in a recent study 2. This resistance occurs because Pseudomonas has multiple intrinsic resistance mechanisms including low outer membrane permeability, efflux pumps that remove antibiotics from the cell, and beta-lactamase enzymes that can inactivate these particular antibiotics.
When treating suspected or confirmed Pseudomonas infections, healthcare providers must specifically select anti-pseudomonal agents rather than these more common antibiotics. This is especially important in healthcare settings, immunocompromised patients, or those with cystic fibrosis where Pseudomonas infections are more common and can be particularly dangerous. A study from 2008 3 demonstrated that P. aeruginosa isolates were highly resistant to ampicillin, amoxicillin, and cefalexin, further supporting the need for specific anti-pseudomonal coverage.
Some key points to consider when choosing an antibiotic for Pseudomonas infections include:
- The use of ceftazidime, carbapenems, or piperacillin-tazobactam as single definitive therapy, as they have been shown to be effective in treating Pseudomonas aeruginosa bacteremia 2
- The potential for resistance to develop, particularly with carbapenems, which had higher rates of resistant P. aeruginosa after treatment 2
- The importance of selecting an antibiotic based on the specific susceptibility pattern of the isolate, when possible.
Overall, the choice of antibiotic for Pseudomonas infections should be guided by the most recent and highest quality evidence, such as the study by 2, which demonstrated that ceftazidime, carbapenems, and piperacillin-tazobactam are effective options for treating Pseudomonas aeruginosa bacteremia.