THE BIOLOGICAL ROLE OF INVASIN DURING A YERSINIA-ENTEROCOLITICA INFECTION

Epidemiological data suggest that the ability to invade the intestinal epithelium of mammals is an essential virulence determinant of Yersin ia enterocolitica. The chromosomally encoded Y. enterocolitica 8081v i nvasion gene, inv, was disrupted to assess its role in pathogenesis. T he inv mutant was unable to invade cultured epithelial cells as effici ently as wild type. Furthermore, when mice were infected intragastrica lly, the inv mutant was extremely deficient at penetrating the murine intestinal epithelium. Analysis of the course of infection showed that the inv mutant had distinct differences relative to wild type in the distribution of visible infectious foci and in tissue colonization; ho wever, the mutant and wild-type strains had similar median lethal dose s for both orally and intraperitoneally infected mice. The invasion de fect 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 i nitial stage of infection. During the subsequent establishment of a sy stemic 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. The possible role of invasin in a naturally occurring Y. enterocolitica infection is discussed.