QCM-D Viscoelastic and Adhesion Monitoring Facilitate Label-Free and Strain-Selective Bacterial Discrimination

Discriminating bacterial adhesion profiles at strain-specific level is crucial for simulating and predicting infections and persistence, as well as developing more efficient antibacterial therapies. Herein, it is proposed that label- and receptor-free bacterial discrimination can be achieved by dynamic viscoelastic and adhesion monitoring over specified timescales using the quartz crystal microbalance with dissipation monitoring (QCM-D). Using two closely related E. coli strains, ATCC 8739 and JM109(DE3), it is shown that their viscoelastic and adhesion properties evolve in time through strain-specific profiles that are clearly distinguishable over a period of 3-4 h. In addition, the viscoelasticity of both E. coli strains shows a strong strain-specific dependence on the medium ionic strength, allowing to further amplify the differences in the bacterial adhesion signatures. Furthermore, the viscoelastic and adhesion behaviors of the two E. coli strains with two additional bacteria, Citrobacter freundii and Serratia marcescens, are compared. For all four bacteria, distinct viscoelastic profiles and adhesion fingerprints emerge over similar timescales that allow to reliably discriminate the various bacteria. These results and similar studies on other bacteria might have pharmacological benefits, for instance, by highlighting the role of bacterial-substrate adhesion and viscoelastic properties on disease pathogenesis and persistence, toward developing more effective therapies.