Effect of shear stress on growth, adhesion and biofilm formation of Pseudomonas aeruginosa with antibiotic-induced morphological changes.

The aim of this study was to investigate the effect of shear stress and antibiotic-induced morphological changes on the growth, adhesion and biofilm formation ability of Pseudomonas aeruginosa. A modified microtitre plate assay was used to quantify adhesion, biofilm formation and planktonic culture density of P. aeruginosa ATCC 27853 under the effect of 0.5x minimal inhibitory concentrations (MICs) of piperacillin/tazobactam, imipenem and meropenem. Hydrodynamic conditions were achieved by orbital shaking at 250 rpm with the presence of a glass bead in each microtitre well. These conditions decreased adhesion and biofilm formation abilities, increased planktonic culture density over 1h and decreased planktonic culture density over 16 h for bacteria with antibiotic-induced morphological changes in comparison with static conditions. Our results demonstrate the importance of using a high-throughput dynamic model to assess the adhesion and biofilm formation behaviour of P. aeruginosa with antibiotic-induced morphological changes and suggest the possible use of sub-MIC antibiotics in clinical applications to prevent infections acquired by haematogenous spread. This dynamic model provides a better simulation of in vivo conditions of adhesion and biofilm formation of P. aeruginosa with altered morphologies induced by beta-lactam antibiotics.