Influence of tetracycline resistance on the transport of manure-derived Escherichia coli in saturated porous media

In this research, tetracycline resistant (tetR) and tetracycline susceptible (tetS) Escherichia coli isolates were retrieved from dairy manure and the influence of tetracycline resistance on the transport of E. coli in saturated porous media was investigated through laboratory column transport experiments. Experimental results showed that tetRE. coli strains had higher mobility than the tetS strains in saturated porous media. Measurements of cell surface properties suggested that tetRE. coli strains exhibited lower zeta potentials than the tetS strains. Because the surface of clean quartz sands is negatively charged, the repulsive electrostatic double layer (EDL) interaction between the tetR cells and the surface of sands was stronger and thus facilitated the transport of the tetR cells. Although no difference was observed in surface acidity, cell size, lipopolysaccharides (LPS) sugar content and cell-bound protein levels between the tetR and tetS strains, they displayed distinct outer membrane protein (OMP) profiles. It was likely that the difference in OMPs, some potentially related to drug efflux pumps, between the tetR and tetS strains led to alteration in cell surface properties which in turn affected cell transport in saturated porous media. Findings from this research suggested that manure-derived tetRE. coli could spread more widely in the groundwater system and pose serious public health risks.

Research highlights
► Tetracycline resistance enhances the mobility of E. coli.
► Tetracycline resistant E. coli strains are more negatively charged.
► TetR and TetSE. coli strains have different outer membrane protein profiles.