CHARACTERIZATION OF PLASMIDS AND PLASMID-ASSOCIATED DETERMINANTS OF YERSINIA-ENTEROCOLITICA PATHOGENESIS

Y. enterocolitica isolates harboring a particular species of plasmid DNA showed a high degree of lethality for gerbils and caused the detachment of HEp-2 [human laryngeal carcinoma cells] monolayers. Strains cured of their plasmid DNA showed loss of these properties. Invasiveness of HEp-2 cells was not a plasmid-mediated property. The expression of plasmid-associated properties, including at least 3 major outer membrane polypeptides, occurred during growth at 37.degree. C but not at 25.degree. C and was related to the concentration of Ca in the growth medium. The plasmid species associated with these properties ranged in molecular mass from 40 .times. 106-48 .times. 106 daltons and comprised a family of related plasmids.