In preliminary studies we found that P. aeruginosa evolves to produce a diverse bacterial population during Cystic Fibrosis (CF) infections. This diversity could increase the stress resistance of the infecting population and its ability to exploit available resources. Changes in infecting population composition could also produce disease flares and blunt the effect of antibiotic treatment. Here we undertake studies to investigate the effect of infecting population diversity in CF lung disease.
Aim 1. How diverse are infecting P. aeruginosa populations in stable CF patients? We will build on our preliminary findings and test the hypotheses that CF P. aeruginosa populations are highly diverse, and that population composition is stable in the absence of overt changes in symptoms. We will measure diversity using complementary techniques that utilize high throughput phenotypic tests and whole genome sequencing of large numbers of isolates.
Aim 2. How does the infecting population change at the onset of exacerbations, and after antibiotic treatment? Exacerbations are likely caused by some change in the stable equilibrium between P. aeruginosa and host. We hypothesize that the composition of P. aeruginosa populations changes at the onset of CF exacerbations, and that these changes could mediate disease flares. We also hypothesize that changes in population composition blunt the effect of antibiotic treatment, as treatment resistant isolates increase in abundance and sustain infection.
Aim 3. Using changes in infecting population composition to understand disease mechanisms. Our ultimate objective is to better understand key disease manifestations in CF. We hypothesize that studying the variant isolates and alleles that change in abundance during clinical transitions will lead us to mechanisms producing exacerbations, and the bacterial functions causing treatment resistance in humans. To accomplish this, we will subject isolates and alleles that significantly increase in abundance during clinical transitions to tests measuring their capacity to produce host cell injury, inflammation, and several mechanisms of antibiotic tolerance.
The P. aeruginosa populations infecting CF patients generally consist of the progeny of a single isolate, and evolution of this strain produces a diverse infecting population. Here we perform initial studies investigating the genetic diversity of infecting P. aeruginosa populations, and seek to understand how this diversity affects infection persistence and disease flares. Knowledge of how genetic diversity and infecting population composition changes affects clinical manifestations (like exacerbations and antibiotic treatment) could lead to new treatment approaches.
| Nguyen, Dao; Joshi-Datar, Amruta; Lepine, Francois et al. (2011) Active starvation responses mediate antibiotic tolerance in biofilms and nutrient-limited bacteria. Science 334:982-6 |
