Effect of stress hormone epinephrine on Pseudomonas aeruginosa biofilm formation
Résumé
Introduction: Hosts signals such as hormones, neurotransmitters or immune system molecules have been shown to modulate the bacterial physiology. Among them, catecholamines hormones epinephrine/norepinephrine, released by stress, physical effort or used therapeutically as inotrope were shown to affect bacterial behaviors of various Gram-negative bacteria. Pseudomonas aeruginosa is an opportunistic pathogen, often involved in nosocomial infections and responsible of chronic infections in immunocompromised patients, which is likely to be in presence of these hormones in human body.
Hypothesis and aims: Biofilm formation of P. aeruginosa is closely related to its virulence and is often implicated in chronic infections. We therefore decided to evaluate the effect of various concentrations of epinephrine on P. aeruginosa biofilm formation.
Methodology: Effect of epinephrine at different concentrations was examined on P. aeruginosa PAO1 biofilm formation under hydrodynamic conditions in a flow-cell system. Bacteria were allowed to attach to the glass side for 2h in presence of epinephrine, and a flow of LB medium (containing epinephrine) was then applied for 24h. Biofilm biovolume and architecture were monitored using Confocal Laser Scanning Microscopy.
Results: Biofilm formation of P. aeruginosa was found to be increased when continuously exposed to epinephrine and this effect depended on the hormone concentration used. A two-fold higher biovolume of the biofilm was seen when the bacteria were exposed to 10 µM of epinephrine. Moreover, microscopic image analysis also showed that epinephrine modified P. aeruginosa adhesion on abiotic surface by inducing cells aggregation.
Conclusion: In this work, P. aeruginosa seems to sense epinephrine stress hormone and respond by increasing its biofilm formation capacity. This result suggests that increase of epinephrine concentration in case of acute stress could promote biofilm formation of P. aeruginosa. A better understanding of these mechanisms and the identification of P. aeruginosa adrenergic putative sensor may be an interesting path to develop new antibacterial strategies against this clinical pathogen.