The effects of the surface charge and hydrophobicity of Escherichia coli on its adhesion to beef muscle

The surface characteristics of Escherichia coli strains were studied to evaluate the effect upon bacterial adhesion to beef muscle. The influence of suspension conditions upon the surface charge of a pathogenic strain, E. coli O157:H7 (EC01), and a saprophytic laboratory strain, E. coli JM109 (EC22) were investigated and compared. The cellular surface charge of most E. coli O157:H7 strains were much less affected by changes in the pH, ionic strength or concentration of surfactants in the suspending medium than was the surface charge of E. coli JM109 cells. Strong adhesion to beef muscle was found in suspending conditions of pH 4 or 10, and with a lowered ionic strength. All E. coli strains tested were negatively charged in 150 mM PBS buffer (pH 7.4) as measured by zeta potentials, ranging from −4.9 to −33.9 mV. Based on the results of adhesion to hexadecane, nine out of 22 strains tested were moderately hydrophobic with about 50% of the cells bound to the solvent. Cellular adhesion of 16 E. coli strains to beef muscle was examined in 150 mM PBS buffer. Generally, O157:H7 strains had lower adhesive properties (Sr value less than 0.10) to beef muscle than other serotypes (up to 0.39). No correlation was found between E. coli cell surface charge, hydrophobicity and adhesion to beef muscle.