INCREASED PROTEIN SECRETION AND ADHERENCE TO HELA-CELLS BY SHIGELLA SPP FOLLOWING GROWTH IN THE PRESENCE OF BILE-SALTS

Growth of Shigella spp. in the presence of the bile salt deoxycholate or chenodeoxycholate enhanced the bacterial invasion of HeLa cells, Gr owth in the presence of other structurally similar bile salts or deter gents had little or no effect. Deoxycholate-enhanced invasion was not observed when bacteria were exposed to deoxycholate at low temperature s or when chloramphenicol was added to the growth medium, indicating t hat bacterial growth and protein synthesis are required. Increased inv asion is associated with the presence of an intact Shigella virulence plasmid and is correlated with increased secretion of a set of protein s, including the Ipa proteins, to the outer membrane and into the grow th medium. The increased invasion induced by the bile salts appears to be due to increased adherence. The enhanced adherence was specific to Shigella spp,, since the enteroinvasive Escherichia coli strains test ed did not exhibit the effect in response to growth in bile salts.