ABSTRACT
A total of 339 Yersinia strains were tested for virulence-associated autoagglutination and hemagglutinin (HA) production. Autoagglutination was frequent among human clinical isolates belonging to Y. enterocolitica serogroups O:3, O:8, and O:9 and among porcine isolates of serogroups O:3 and O:9. Positive autoagglutination results were also observed in serogroups O:1 and O:2, associated with outbreaks among chinchillas, hares, and goats. All of 164 environmental isolates were negative in the autoagglutination assay. When subcultured serially in nutrient broth, none of the clinical isolates produced HA at either 22 or 37 degrees C, whereas 22.6% of the environmental yersiniae yielded mannose-resistant HA (MRHA). Six different MRHA patterns were recorded. Eighteen strains, all of which produced MRHA in nutrient broth, yielded similar MRHA patterns after cultivation on colonization factor agar. None of the autoagglutination-positive-(AA+) strains produced MRHA in either nutrient broth or on colonization factor agar. In contrast, a distinct autoagglutination-associated MRHA was detected after growth in Eagle minimal essential medium. Comparison of AA+ and autoagglutination-negative (AA-) derivatives of serogroups O:2, O:3, O:5, O:8, and O:9 showed that all AA+ cultures produced MRHA when grown in minimal essential medium at 37 degrees C overnight, whereas no MRHA was observed with any of the AA- derivatives of the same serogroups. This autoagglutination associated MRHA reacted with guinea pig erythrocytes, but not with erythrocytes from seven other species.
