The Role of Alginate and Extracellular DNA in Biofilm-Mediated Pseudomonas aeruginosa Gentamicin Resistance

The role of extracellular DNA in gentamicin resistance of Pseudomonas aeruginosa biofilms was examined in the presence and absence of alginate, a major component of the bacterial biofilm. A PAO1 P. aeruginosa variant with a chromosomal lux gene insertion was used to measure bacteria viability during experimentation. Mature biofilms grown in cation-adjusted Mueller-Hinton media were treated with alginate lyase, deoxyribonuclease, or both, and resistance to gentamicin was examined by bioluminescence measured over 2 hours. All enzymatic digestions resulted in increased susceptibility to gentamicin treatment, with both enzymes in conjunction having a maximized effect on antibacterial sensitivity. The findings indicate that extracellular DNA is a partial determinant of P. aeruginosa biofilm-mediated resistance to gentamicin. The combination of alginate lyase and deoxyribonuclease treatment of P. aeruginosa infections may be beneficial prior to administration of antibiotics and warrants further investigation.