Yersinia enterocolitica invasin: a primary role in the initiation of infection.

The ability to invade the intestinal epithelium of mammals is an essential virulence determinant of Yersinia enterocolitica. The chromosomally encoded Y. enterocolitica 8081v invasion gene, inv, was disrupted to assess its role in pathogenesis. The inv mutant (JP273v) was approximately 80-fold less invasive than wild type for cultured epithelial cells. When mice were infected intragastrically, up to 10(7) fewer JP273v were recovered from Peyer's patches early (6-18 hr) after infection compared with wild type. Analysis of the course of infection revealed that the inv mutant had distinct differences relative to wild type in the distribution of visible infectious foci and in tissue colonization; however, the mutant and wild-type strains had similar LD50 values for both orally and intraperitoneally infected mice. The invasion defect of the inv mutant was fully complemented in vitro and in vivo by introduction of the wild-type inv gene in trans. The inv gene product, invasin, appears to play a vital role in promoting entry during the initial stage of infection. During the subsequent establishment of a systemic infection, invasin may be of secondary importance, since the Y. enterocolitica inv mutant was as proficient as wild type at causing a fatal infection in mice. Based on these data, we discuss the role of invasin in a naturally occurring Y. enterocolitica infection.