Exploring the clinical potential of quorum sensing molecules as novel biomarkers for airway infection with Pseudomonas

Pseudomonas aeruginosa (PA) is a bug that affects susceptible individuals including those with cystic fibrosis (CF) and burns. It is an important factor that contributes to the reduced survival of patients with CF (whose life expectancy is 30-40 years less than in those without this disease). Recently, one in three of patients with chest disorders related to smoking such as bronchitis and emphysema have been demonstrated to have PA infection (much higher levels than was previously appreciated). This is important, as these chest diseases are common, and the antibiotics used to treat PA infection are different to those used to treat other infections. Hence, in the absence of an accurate blood test to diagnose PA infection, patients may be given the wrong antibiotic treatment. This may also increase the risk of the developing of drug-resistant bacteria. This is especially important in infection with PA as this bug rapidly develops resistance to antibiotics and the number of effective antibiotics available is limited.

There is a pressing need for new, improved tests to allow rapid diagnosis and treatment of patients with PA infection. A new test for bacterial signal molecules of PA infection has been developed at the University of Nottingham. This proposal will collect sputum, blood, urine and saliva samples from individuals with cystic fibrosis and assess if the new test can be used as a direct measure of PA infection in these samples, comparing the new test with the tests for PA infection that are currently available. The research will also determine whether the new test has potential in permitting early detection of those who do not respond to antibiotic treatment, or detecting those who may have early PA infection that cannot be detected using current microbiological techniques. At present assessment of bacterial signal molecules is expensive and can only be done in a very small number of research institutions. This proposal will also test a new method of measuring these molecules so that it would be widely available to all those who need it.

In this multidisciplinary application we will capitalise on expertise ranging from laboratory scientists to clinicians supported by the infrastructure created by the new National Institute for Health Research Respiratory Biomedical Research Unit in Nottingham. We anticipate that if successful, the new assay will be available for clinical use within 1-2 years of the completion of the study.

Background: The bacterium Pseudomonas aeruginosa (PA) results in serious lung infections and is the leading cause of ill health and death in patients with cystic fibrosis (CF) and bronchiectasis. PA infection is also increasingly important with regard to chronic obstructive pulmonary disease (COPD); infection with PA being detected in 30% of patients with this condition. There is a pressing need to develop new biomarkers for PA infection that will facilitate diagnosis in the early stages in infection. This will also permit assessment of response to antibiotic therapy and may reduce inappropriate exposure to broad spectrum antibiotics.

Our preliminary studies have shown that quorum sensing (QS) molecules are produced during infection with PA and represent a novel biomarker for PA infection. This proposal aims to determine if QS molecules in a variety of biological samples are 1) correlated with quantitative measures of PA infection; 2) have potential to guide the treatment of exacerbations in patients with CF, and 3) can predict the progression of CF respiratory disease. We will also assess the potential of new technologies that can measure QS molecules using an affordable quantitative technique.

Methods: The study population will consist of the well characterised Nottingham CF Cohort (140 adults and 180 children). Sputum, blood, urine and saliva samples will be collected from eligible patients. Quantitative microbiological techniques will generate a gold standard for the infective load of PA, and liquid chromatography/mass spectrometry will measure the QS levels in the biological fluids collected.
Specifically the proposal will address the following questions in three clinical studies:
1. Are QS molecules in the sputum, blood, saliva and urine correlated with quantitative microbiological culture of PA from sputum?
2. Are QS molecules in the sputum, blood, saliva and urine sensitive to treatment with anti-pseudomonal antibiotic therapy during treatment of infective exacerbations?
3. What is the prevalence of detectable blood QS levels in a paediatric population and does this predict future PA infection and CF disease progression?

We will capitalise on the availability of world leading molecular microbiology expertise coupled with a strong clinical cystic fibrosis research team and the translational infrastructure created by the new NIHR Respiratory Biomedical Research Unit in Nottingham. The proposal aims to test novel biomarkers of PA infection in collaboration with a commercial partner that if successful would result in the clinical benefits of the new biomarkers being potentially available 1-2 years later.