Quorum-sensing signals indicate that cystic fibrosis lungs are infected with bacterial biofilms

Area of Science:

• Microbiology
• Medical Science
• Biochemistry

Background:

• Pseudomonas aeruginosa frequently colonizes cystic fibrosis lungs despite antibiotic treatment.
• This suggests the bacterium may form biofilms—structured, matrix-encased communities—within the lungs.
• Microscopy of cystic fibrosis sputum confirms P. aeruginosa in biofilm-like structures.

Purpose of the Study:

• To investigate the role of quorum-sensing signals in P. aeruginosa biofilm formation within cystic fibrosis sputum.
• To analyze the relative abundance of quorum-sensing signals in cystic fibrosis sputum compared to laboratory conditions.
• To assess the potential of quorum-sensing signal profiling as a biomarker for identifying anti-biofilm agents.

Main Methods:

• Microscopic analysis of cystic fibrosis sputum to identify bacterial structures.
• Quantification of two principal P. aeruginosa quorum-sensing signals in sputum and laboratory cultures.
• Cultivation of P. aeruginosa isolates from sputum and the standard strain PAO1 in broth and a laboratory biofilm model.

Main Results:

• Cystic fibrosis sputum contains the two main P. aeruginosa quorum-sensing signals, but in reversed relative abundance compared to standard laboratory cultures.
• Some P. aeruginosa sputum isolates exhibited standard signal ratios in broth, but shifted to sputum-like ratios in a laboratory biofilm model.
• Laboratory biofilm models replicated the reversed signal ratios observed in cystic fibrosis sputum.

Conclusions:

• The findings support the hypothesis that P. aeruginosa exists as biofilms in cystic fibrosis sputum.
• Quorum-sensing signal profiling of P. aeruginosa strains shows promise as a biomarker.
• This profiling could aid in screening for novel agents that disrupt P. aeruginosa biofilm development.