ASSESSMENT OF PLASMID PROFILE EXOENZYME ACTIVITY AND VIRULENCE IN RECENT HUMAN ISOLATES OF YERSINIA-ENTEROCOLITICA

A group of 23 recent clinical isolates of Y. enterocolitica recovered from symptomatic patients residing in the New York, New York, USA area were examined. These isolates were tested for the presence of plasmids, exoenzyme activity, mouse lethality, and phenotypic properties postulated to correlate with virulence. Of the 23 isolates, 17 harbored a 60-65 kilobase (kb) plasmid. Six isolates were lethal for white mice, showed the phenotypic markers of autoagglutination and Ca dependence for growth at 37.degree. C, and contained a 60-65 kb plasmid. Restriction endonuclease analysis with several different enzymes revealed the presence of 3 distinct plasmid profiles in these isolates. Isolates with a single plasmid of 60-70 kb, typical for this species, were detected, but these were of 3 distinct types as judged from restriction enzyme digestion. One strain was unusual among clinical isolates of Y. enterocolitica in that it contained at least 4 distinct plasmids. In addition, this nontypable strain showed exoenzymatic activity similar to that of serogroup 08 isolates, was not lethal to mice, and did not require Ca for growth at 37.degree. C.