Standard versus biofilm antimicrobial susceptibility testing to guide antibiotic therapy in cystic fibrosis

Valerie Waters, Felix Ratjen

The antibiotics used to treat pulmonary infections in people with cystic fibrosis are typically chosen based on the results of antimicrobial susceptibility testing performed on bacteria traditionally grown in a planktonic mode (grown in a liquid). However, there is considerable evidence to suggest that Pseudomonas aeruginosa actually grows in a biofilm (or slime layer) in the airways of people with cystic fibrosis with chronic pulmonary infections. Therefore, choosing antibiotics based on biofilm rather than conventional antimicrobial susceptibility testing could potentially improve response to treatment of Pseudomonas aeruginosa in people with cystic fibrosis. This is an update of a previously published Cochrane Review. To compare biofilm antimicrobial susceptibility testing-driven therapy to conventional antimicrobial susceptibility testing-driven therapy in the treatment of Pseudomonas aeruginosa infection in people with cystic fibrosis. We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. Most recent search: 19 June 2017.We also searched two ongoing trials registries and the reference lists of relevant articles and reviews. Most recent searches: 24 August 2017 and 05 September 2017. Randomized controlled trials of antibiotic therapy based on biofilm antimicrobial susceptibility testing compared to antibiotic therapy based on conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infection in people with cystic fibrosis. Both authors independently selected trials, assessed their risk of bias and extracted data from eligible trials. Additionally, the review authors contacted the trial investigators to obtain further information. The quality of the evidence was assessed using the GRADE criteria. The searches identified two multicentre, randomized, double-blind controlled clinical trials eligible for inclusion in the review with a total of 78 participants (adults and children); one trial was done in people who were clinically stable, the other in people experiencing pulmonary exacerbations. These trials prospectively assessed whether the use of biofilm antimicrobial susceptibility testing improved microbiological and clinical outcomes in participants with cystic fibrosis who were infected with Pseudomonas aeruginosa. The primary outcome was the change in sputum Pseudomonas aeruginosa density from the beginning to the end of antibiotic therapy.Although the intervention was shown to be safe, the data from these two trials did not provide evidence that biofilm susceptibility testing was superior to conventional susceptibility testing either in terms of microbiological or lung function outcomes. One of the trials also measured risk and time to subsequent exacerbation as well as quality of life measures and did not demonstrate any difference between groups in these outcomes. Both trials had an overall low risk of bias and the quality of the evidence using GRADE criteria was deemed to be moderate to high for the outcomes selected. The current evidence is insufficient to recommend choosing antibiotics based on biofilm antimicrobial susceptibility testing rather than conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infections in people with cystic fibrosis. Biofilm antimicrobial susceptibility testing may be more appropriate in the development of newer, more effective formulations of drugs which can then be tested in clinical trials.