Cystic fibrosis is a major genetic disease in many populations, and has been transformed from a life ending, to a life-shortening disease through aggressive therapy especially that aimed at the major pathogen in CF P. aeruginosa. However, there is no currently available method to rapidly determine whether a CF patient is actively infected with P. aeruginosa or to assess whole-lung bacterial levels.
The progressive lung damage and deterioration of respiratory function in cystic fibrosis (CF) arises from a characteristic pattern of bacterial colonization of the lung, with chronic Pseudomonas aeruginosa infections being centrally important to the lung pathology and progressive tissue damage in CF patients. More than 80% of CF patients over 26 years old are chronically infected with P. aeruginosa, and these infections persist, despite aggressive antibiotic therapy. After initial infection with wild-type, non-mucoid strains, exemplified by strains such as PAO1, conversion of P. aeruginosa to the mucoid phenotype in the CF host occurs and increases bacterial resistance not only to host clearance and defense mechanisms, but also to antibiotic interventions. The mucoid phenotype is characterized by production of large amounts of the exopolysaccharide alginate. Mucoid conversion is concomitant with the establishment of chronic bacterial colonization and increases inflammation and lung damage, while causing pulmonary function to decline. Furthermore, alginate modulates host defenses to allow a persistent infection. Accordingly, mucoid conversion results in a poor prognosis for CF patients to heal
Rapidly knowing if mucoid conversion has occurred, and the extent of mucoid pseudomonas burden would greatly improve therapies. However, there is no currently available method to rapidly determine whether a CF patient is infected, or colonized with mucoid R aeruginosa or to assess whole-lung mucoid bacterial levels. Currently, culture of sputum samples, or bronchioalveolar lavage, together with phenotypic (and genotypic) analysis. We propose a novel detection system that will revolutionize mucoid bacterial detection, and so management of CF. By making key modifications to current H pylori breath test, we will furnish a specific and selective test for the presence and bacterial load of mucoid P aeruginosa in CF lungs.
An H. pylori breath test is presently available for detecting H. pylori levels in the gut of patient. The basis for the H pylori breath test is that a drink containing labeled urea (carbon-13 or carbon-14) is ingested, with the urea rapidly encountering urease-positive H. pylori bacteria in the gut (if the bacteria is present) that break down the urea into labeled CO2 that is detected in the breath about 15 minutes afterwards.
P. aeruginosa also expresses urease1-4, has the urease urea-ureG gene cluster whose expression is modifiable (Deretic & Timmins, unpublished microarray data), and consequently, is susceptible to detection by breath tests if the appropriate technology is developed and applied. Because P. aeruginosa is so exquisitely associated with the CF lung, and not the normal population, by targeting the CF patient, high specificity can be achieved.