Testing antibiotics in combination for acute infections of Pseudomonas aeruginosa in cystic fibrosis

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Review question

We reviewed the evidence about the effect of testing antibiotics in combination for acute airway infections in people with long-term (chronic) infection with Pseudomonas aeruginosa.


The main cause of death in people with cystic fibrosis is chronic lung infection. People with cystic fibrosis now live longer due to the aggressive use of antibiotics to treat lung infections. Traditionally, antibiotics are chosen based on the results of laboratory testing of each antibiotic separately against the bacterium (or bug) that is found in the lungs of the person with cystic fibrosis. Antibiotics tested in combination may work effectively against a bacterium even if not effective when tested alone. However, when choosing antibiotics to treat lung infections caused by Pseudomonas aeruginosa in people with cystic fibrosis, it is unclear whether basing the choice of antibiotics on the results of combination testing is better than basing choice on the results of testing antibiotics separately.

This is an updated version of a previously published review.

Search date

The evidence is current to: 19 December 2016.

Study characteristics

The search identified one study that tried to answer this question and was eligible for inclusion in the review. The study enrolled 132 people with cystic fibrosis, most of whom (82 people) had acute lung infections with Pseudomonas aeruginosa, and randomly put them into two treatment groups. In the first group two antibiotics were selected following the testing of combinations of antibiotics and in the second group the two antibiotics were chosen after testing individual antibiotics to see how effective the drugs were against the bacterium. The study was run across several centres and assessed the clinical outcomes in the participants after a 14-day course of treatment.

Key results

The study investigators were only able to provide us with data for those who were infected with Pseudomonas aeruginosa for their main outcome (the time until the next acute lung infection). Choosing antibiotics based on the results of combination antibiotic testing did not lead to a longer time until the next lung infection compared to choosing antibiotics based on results of separate testing. They could not provide us with any results people infected with Pseudomonas aeruginosa for other outcomes in our review.

Quality of the evidence

We are satisfied that the people taking part were divided into the different treatment groups completely at random and no one could have foreseen which group any individual would be in. We are also satisfied that during the study, neither the individuals or clinic personnel knew which treatment group each individual was in. There were no missing data from the study. The quality of the evidence for the only outcome for which we have data (time to the next lung infection) is moderate, but we could not judge the quality of the evidence for other outcomes as there were no separate results available for people infected with Pseudomonas aeruginosa.