Adherence of Shigella flexneri to guinea pig intestinal cells is mediated by a mucosal adhesin

Abstract

Guineapig colonic epithelial cells released by treating sections of the colon with solutions containing EDTA, dithiothreitol, and citrate avidly adhered Shigella flexneri bacteria. Separation of the intestinal cells from nonbound bacteria was achieved by differential sedimentation on a Percoll gradient. Adherence of S. flexneri to the colonic cells was Ca2+ (1 mM) and time dependent. The pH optimum was pH 6.2, and almost no attachment (<5%) was observed at low temperature (4°C). The average number of bacteria which bound to colonic cells was 70 bacteria per cell, whereas attachment to cells isolated from the ileum region was 6 bacteria per cell. Colonic cells obtained from the intestine of rabbits or rats did not adhere Shigella. Adherence to guinea pig colonic cells was inhibited (50%) by several carbohydrates, such as 0.1% fucose or 0.5% glucose, as well as by a lipopolysaccharide preparation (10 μg/ml) isolated from S. flexneri. Fixation of the bacteria with glutaraldehyde or preincubation of the bacteria with lectins or proteolytic enzymes did not affect their adherence. Proteolytic digestions or fixation of the epithelial cells, as well as pretreatments with lipopolysaccharide or fucose solutions, abolished their ability to adhere bacteria. These results indicate that a carbohydrate-binding substance on the surface of guinea pig colonic epithelial cells is responsible for the attachment of the Shigella bacilli.