Examination of the envelope antigen K1 in Yersinia enterocolitica which was identified as fimbriae.

The envelope antigen K1 found in the majority of Yersinia enterocolica (Y. ent.) strains belonging to the O group 10 as described by WAUTERS, was re-examined under the electron microscope, and identified as being fimbriae. These fimbriae envelop the bacterial cell with a dense fringe. Single filaments show a width of 2.5 to 1.7 nm whilst their length is variable, often many times the size of the bacterial cell. Fimbriated Y. ent. cultures do not form pellicle, and the haemagglutination test is negative. They are O and fimbriae agglutinable. Test results for the acknowledged 3 antigenic differences, i.e. agglutinability, agglutinin-binding capacity and agglutinogenic capacity showed that: 1. there is a certain thermo-lability as to the agglutinability. For its total suppression, half-an-hour's boiling at 120 degrees C of the culture fim+ is necessary. Chemical treatment of such a culture hardly impairs the agglutinability of fimbriae. 2. the agglutinin-binding (= absorbing) capacity of the fimbrial antigen is little affected by continuous heating, even up to 3 hrs. However, at least half-an-hour's boiling at 120 degrees C or alternatively chemical treatment with 50% alcohol or nHC1 practically destroys this ability. 3. The heating process has a significant and progressive effect on the agglutinogenic capacity of the Y. ent. fimbriae which is destroyed irrevocably after 30 mins. boiling at 120 degrees C. Chemical treatment hardly affects this character. It is recommended to use a formalised culture Y. ent. fim+ for the preparation of a specific Y. ent. fimbrial serum. For the elimination of O antibodies, this antiserum should be absorbed with a strain fim- of the same O group. Provided the strain was incubated at 37 degrees C, no H absorption is required, because Y. ent. strains do not form flagella at that incubation temperature.