[16] Bacterial Lectinlike Adhesins: Determination and Specificity

This chapter presents the experimental procedures employed in studies on Escherichia coli lectinlike adhesins, focusing on models for testing adhesins and for determining glycoprotein receptors of the adhesins. Bacterial lectinlike adhesins are proteinaceous structures located on the surface of bacterial cells that mediate the specific adhesion of the bacteria to the host cells. These recognizing proteins bind to the sugar components of glycoproteins or glycolipids on the surface of target cells. The capacity of bacteria to bind specifically to host cells is considered an important virulence factor involved in the initial step of infection. The hemagglutination (HA) test is used for the detection and characterization of lectins. The large natural variability of glycoproteins and glycolipids on the surface of erythrocytes (RBCs) of various animal species provides a tool for evaluating the specificity of bacterial adherence. The HA activity of group I strains of E. coli, defined as carrying type I fimbriae, is best developed in a stationary phase of bacterial culture grown in liquid medium at 37°. The HA activity may be expressed, albeit less strongly, in a culture grown at 20 ° or on solid medium. The hemagglutinins (adhesins) of E. coli are usually associated with fimbrial structures protruding from bacterial surfaces.