IN-VITRO AND IN-VIVO CHARACTERIZATION OF AN AIL MUTANT OF YERSINIA-ENTEROCOLITICA

Ail is a 17-kDa protein of Yersinia enterocolitica previously identifi ed on the basis of its ability to confer upon Escherichia call the phe notype of attachment and invasion of cultured epithelial cells. Here w e report an examination of the contribution of ail to the pathogenicit y of Y. enterocolitica. A low copy-number ail plasmid that promoted se rum resistance in E. coli HB101 was constructed. The serum resistance phenotype conferred by ail to E. coli was affected by the growth phase of the culture as well as by the gene copy number. In Contrast, the c opy number of ail (and the relative quantity of Ail) was found to have little effect on the amount of Ail promoted invasion of cultured epit helial cells. An ail mutant of Y. enterocolitica was constructed and c haracterized in vitro. This mutant produced no detectable Ail and had a reduced ability to invade CHO cells. Serum resistance of Y. enteroco litica was Ail dependent and was affected by growth phase and ail copy number. The phenotype of the ail mutant was examined in vivo by using a murine model for infection. The ail mutant phenotype was identical to that of the wild-type strain in oral 50% lethal dose studies and ea rly colonization of Peyer's patches as well as in kinetic studies. Wes tern blot (immunoblot) analysis of Ail produced by bacteria growing in vivo at 48 h postinfection indicated that ail was expressed at this t ime point. Thus, our findings confirm that Ail contributes to the seru m resistance and invasion phenotypes of Y. enterocolitica in vitro and indicate that Ail is not required to establish an infection or to cau se systemic infection of BALB/c or DBA/2 mice.