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

Abstract

The bacterium Pseudomonas aeruginosa permanently colonizes cystic fibrosis lungs despite aggressive antibiotic treatment. This suggests that P. aeruginosa might exist as biofilms--structured communities of bacteria encased in a self-produced polymeric matrix--in the cystic fibrosis lung. Consistent with this hypothesis, microscopy of cystic fibrosis sputum shows that P. aeruginosa are in biofilm-like structures. P. aeruginosa uses extracellular quorum-sensing signals (extracellular chemical signals that cue cell-density-dependent gene expression) to coordinate biofilm formation. Here we found that cystic fibrosis sputum produces the two principal P. aeruginosa quorum-sensing signals; however, the relative abundance of these signals was opposite to that of the standard P. aeruginosa strain PAO1 in laboratory broth culture. When P. aeruginosa sputum isolates were grown in broth, some showed quorum-sensing signal ratios like those of the laboratory strain. When we grew these isolates and PAO1 in a laboratory biofilm model, the signal ratios were like those in cystic fibrosis sputum. Our data support the hypothesis that P. aeruginosa are in a biofilm in cystic fibrosis sputum. Moreover, quorum-sensing signal profiling of specific P. aeruginosa strains may serve as a biomarker in screens to identify agents that interfere with biofilm development.

Proteomic analysis of Pseudomonas aeruginosa grown under magnesium limitation

“…These results provide a strong functional correlation between LPS modification enzyme levels and the LPS structural modifications seen in this environmental condition, confirming the validity of ICAT analysis. A number of P. aeruginosa virulence factors are regulated by quorum sensing bacterial communication via small molecule signals N-(3-oxododecanoyl)-L-homoserine lactone (3OC12-HSL) and N-butyryl-L-homoserine lactone (C4-HSL) [24,25,26,13]. The quantitative protein profiles indicated that magnesium limitation induced several quorum sensing proteins including the 3OC12-HSL synthase LasI [27] and the starvation and general stress-response regulator RelA [28,29] (Table 2).…”

“…The result of such envelope modification is increased bacterial resistance to antimicrobial peptides [10,11] and increased proinflammatory signaling through the human Tlr4 receptor [12]. P. aeruginosa was also isolated from CF patients' airways in the form of biofilms, antibiotic-resistant bacterial communities [13]. Some of the properties that are characteristic for clinical isolates of P. aeruginosa, such as synthesis of CF-specific LPS, can be also induced in vitro by growth of the bacteria in medium limited for magnesium.…”

Pseudomonas aeruginosa flagellum is critical for invasion, cutaneous persistence and induction of inflammatory response of skin epidermis

“…Moreover, T3SS in vitro detection was correlated with increased morbi-mortality and relapse in human P. aeruginosa ventilator-associated pneumonia and blood stream infections [55,56]. Previously, T2SS has been shown to be strongly involved in P. aeruginosa chronic infection [57]. In this work, the absence of functional T2SS or T3SS was not associated with significant decrease of the main inflammatory mediator expression by infected monolayered keratinocytes at an early time of infection (6 h).…”

Clinafloxacin for Treatment of Burkholderia cenocepacia Infection in a Cystic Fibrosis Patient

“…Specifically, in comparison to a number of other fluoroquinolones, clinafloxacin was noted to be the most active against efflux-mediated multidrug-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Burkholderia cepacia, all recognized pathogens in CF patients (14). This is particularly relevant in the treatment of CF pulmonary infections that are characterized by biofilms, or matrix-encased communities of bacterial cells (26). Efflux pumps play a significant role in biofilmspecific resistance to multiple classes of antibiotics, including fluoroquinolones, in bacteria such as B. cenocepacia (27,28).…”