D-amino acids do not inhibit Pseudomonas aeruginosa biofilm formation.

OBJECTIVE: Pseudomonas aeruginosa , a known biofilm-forming organism, is an opportunistic pathogen that plays an important role in chronic otitis media, tracheitis, cholesteatoma, chronic wounds, and implant infections. Eradication of biofilm infections has been a challenge because the biofilm phenotype provides bacteria with a protective environment from the immune system and antibiotics; thus, there has been great interest in adjunctive molecules that may inhibit biofilm formation or cause biofilm dispersal. There are reports that D-amino acids may inhibit biofilms. In this study, we test the ability of various D-amino acids to inhibit P. aeruginosa biofilm formation in vitro.

STUDY DESIGN: We evaluated the effect of D-alanine (10 mM), D-leucine (10 mM), D-methionine (10 mM), D-tryptophan (10 mM), and D-tyrosine (10 uM and 1 mM) on biofilm formation in two commonly studied laboratory strains of P. aeruginosa : PAO1 and PA14.

METHODS: Biofilms were grown in 24-well and 96-well tissue culture plates, documented photographically and stained with 0.1% crystal violet and solubilized in 33% glacial acetic acid for quantification.

RESULTS: In strains PAO1 and PA14, the addition of D-amino acids did not result in an inhibitory effect on biofilm growth in 24-well plates. Repeating the study in 96-well plates confirmed our findings that D-amino acids do not inhibit biofilm formation of P. aeruginosa .

CONCLUSION: We conclude that D-amino acids only slow the production of biofilms rather than completely prevent biofilm formation; therefore, D-amino acids represent a poor option for potential clinically therapeutic interventions.

LEVEL OF EVIDENCE: N/A.