Pathogenicity of nine human Yersinia enterocolitica isolates  of Iran   were    

   tested  by   serological  tests   and  molecular  approaches.  Of  these  nine

   isolates two harbored a plasmid (1478 & 1479). These  two  isolates  showed

   different  patterns of total proteins compared with others.

     Autoagglutination (AA) and resistance to the bactericidal effect of human    

   serum tests(SR) used to  differentiate between virulent and avirulent isolates

   of  Y. enterocolitica.  Isolates  1478 and 1479 showed to be AA⁺ / SR⁺ where

   as others were AA^- / SR^- .

     With these findings it  is evident   that  the  serological tests can be used to    

   identify  virulent from avirulent isolates.