Effect of antimicrobial residues on early adhesion and biofilm formation by wild-type and benzalkonium chloride-adapted Pseudomonas aeruginosa

Abstract

Antimicrobial residue deposition can change the physico-chemical properties of bacteria and surfaces and thus promote or impair bacterial adhesion. This study focuses on benzalkonium chloride (BC) deposition on polystyrene (PS) surfaces and the influence of this conditioning film on the physico-chemical properties of PS and on early adhesion and biofilm formation by Pseudomonas aeruginosa wild-type and its laboratory BC-adapted strain. The latter readily acquired the ability to grow in BC, and also exhibited physico-chemical surface changes. The existence of residues on PS surfaces altered their hydrophobicity and favoured adhesion as determined by the free energy and early adhesion characterization. Adapted bacteria revealed a higher ability to adhere to surfaces and to develop biofilms, especially on BC-conditioned surfaces, which thereby could enhance resistance to sanitation attempts. These findings highlight the importance of investigations concerning the antimicrobial deposition effect after cleaning procedures, which may encourage bacterial adhesion, especially of bacteria that have been previously exposed to chemical stresses.

Keywords:

• conditioning film
• Pseudomonas aeruginosa
• early adhesion
• biofilm formation
• physico-chemical properties
• adaptive resistance
• antimicrobial residues

Acknowledgements

Financial support from IBB-CEB and Fundação para a Ciência e Tecnologia (FCT) and the European Community fund FEDER, through the Program COMPETE, in the ambit of Project PTDC/SAUESA/64609/2006 /FCOMP-01-0124-FEDER-00702, Idalina Machado's PhD Grant (SFRH/BD/31065/2006) and Susana Lopes’ PhD Grant SFRH/BD/47613/2008) are gratefully acknowledged.