Outer membrane proteins and plasmids in different Yersinia enterocolitica serogroups isolated from man and animals

Human clinical isolates of Yersinia enterocolitica (serogroups 0:3, 0:8, and 0:9) harboured a 40-45 megadaltons plasmid, which was shared by strains isolated from cases of yersiniosis in animals (0:2 and 0:5) and from healthy swine (0:3 and 0:9). Possession of such plasmids was invariably correlated with expression of three temperature-regulated characteristics related to the bacterial surface: when cultivated at 37 degrees C, all plasmid-bearing strains, unlike their plasmid-cured mutants, (i) underwent autoagglutination, (ii) produced a distinct mannose-resistant haemagglutinin, and (iii) simultaneously synthesized ancillary outer membrane proteins (OMPs). None of these characters was expressed phenotypically at 22 degrees C. Dominant among the plasmid-associated, temperature-regulated OMPs was a high molecular weight protein of approximately 180 kilodaltons, which was found in strains of five different serogroups (0:2, 0:3, 0:5, 0:8, and 0:9) regardless of the source of isolation. Strains isolated from diseased animals and from healthy swine were quite similar, if not identical, to human clinical isolates with respect to these ancillary OMPs. In contrast to the plasmid-associated OMPs expressed only at 37 degrees C, a number of plasmid-independent OMPs were produced mainly at 22 degrees C.