The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methyl methacrylate) (PMMA), poly(hydroxyethyl methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-Cl). Bacterial and polymer surfaces were characterized by means of water contact angles and zeta potentials. Both the sessile drop contact angles and the zeta potentials of the bacterial surfaces were significantly different. No significant differences in the sessile drop contact angles of the polymer surfaces were observed. Using the Wilhelmy plate technique large contact angle hysteresis was observed for the different polymer surfaces. Surfaces of copolymers with MAA had more negative zeta potentials than those of the corresponding homopolymers. Surfaces of copolymers with TMAEMA-Cl had positive zeta potentials. The highest numbers of adherent bacteria were found on materials with positive zeta potentials, irrespective of the bacterial strain used. Bacterial adhesion on to copolymers with MAA was less than on to the corresponding homopolymers. Bacterial equilibrium adhesion values correlate with the zeta potentials of the polymer surfaces (r greater than 0.85). On substrates with less negative zeta potentials high numbers of adhered bacteria were observed. Additionally, the equilibrium bacterial adhesion values could be related with receding contact angles of polymer surfaces with negative zeta potentials (r greater than 0.86). High equilibrium adhesion values were obtained for polymers with high contact angles. No correlation between the zeta potentials and contact angles of the bacteria with the adhesion values was found.

Eight Escherichia coli strains were characterized by determining their adhesion to xylene, surface free energy, zeta potential, relative surface charge, and their chemical composition. The latter was done by applying X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy OR). No relationship between the adhesion to xylene and the water contact angles of these strains was found. Three strains had significantly lower surface free energies than the other strains. Surface free energies were either obtained from polar and dispersion parts or from Lifshitz-van der Waals and acid/base parts of the surface free energy. A correlation (r = 0.97) between the polar parts and the electron-donor contributions to the acid/base part of the surface free energy was found. The zeta potentials of all strains, measured as a function of pH *Author to whom all correspondence and reprint requests should be addressed. Cell Biophysics 1 7Volume 20, 1992 18Harkes et al.(2-11), were negative. Depending on the zeta potential as a function of pH, three groups were recognized among the strains tested. A relationship (r = 0.84) was found between the acid/base component of the surface free energy and the zeta potential measured at pH = 7.4. There was no correlation between results of XPS and IR studies. Data from the literature of XPS and IR studies of the gram-positive staphylococci and streptococci were compared with data from the gram-negative E. coli used in this study. It appeared that in these three groups of bacteria, the polysaccharide content detected by IR corresponded well with the oxygen-to-carbon ratio detected by XPS.

An in vitro system was developed to study the migration of uropathogenic Escherichia coli strains. In this system an aqueous agar gel is placed against a solid surface, allowing the bacteria to migrate along the gel/solid surface interface. Bacterial strains as well as solid surfaces were characterized by means of water contact angle and zeta potential measurements. When glass was used as the solid surface, significantly different migration times for the strains investigated were observed. Relationships among the observed migration times of six strains, their contact angles, and their zeta potentials were found. Relatively hydrophobic strains exhibited migration times shorter than those of hydrophilic strains. For highly negatively charged strains shorter migration times were found than were found for less negatively charged strains. When the fastest-migrating strain with respect to glass was allowed to migrate along solid surfaces differing in hydrophobicity and charge, no differences in migration times were found. Our findings indicate that strategies to prevent catheterassociated bacteriuria should be based on inhibition of bacterial growth rather than on modifying the physicochemical character of the catheter surface. * Corresponding author. water contact angle, whereas the surface charge was determined by measuring the zeta potential, which is a measure of the surface charge.

The adhesion and growth of two catheter-associated (O2K2 and O83K?) and two non catheter-associated (O111K58 and O157K-) uropathogenic Escherichia coli strains on glass, poly(methyl methacrylate) (PMMA), a negatively charged copolymer of MMA and methacrylic acid (MAA) and a positively charged copolymer of MMA and trimethylaminoethyl methacrylate chloride (TMAEMA-Cl) were studied. The solid surfaces were placed in a parallel plate perfusion system. After preadhesion of the bacteria onto the surfaces, growth was initiated by perfusing the system with MacConkey broth. Growth was measured by counting adherent bacteria as a function of time. Bacterial strains were characterized by means of water contact angle, microbial adhesion to hydrocarbon (MATH), anion exchange resin retention (ARR) and zeta potential measurements. Solid surfaces were characterized by means of water contact angle and zeta potential measurements. The catheter-associated strains had significantly higher water contact angles, zeta potentials and ARR values than the non catheter-associated strains. Non catheter-associated strains did not grow at the surfaces used. Catheter-associated strains did not grow at the positively charged surface but exhibited growth at the other surfaces. Strains grew more rapidly at surfaces with a relatively high negative zeta potential and a low water contact angle than at surfaces with a relatively low negative zeta potential and a high water contact angle. The growth of strain O2K2 on glass was significantly reduced when urine instead of MacConkey broth was used as perfusion medium.