Detection by using monoclonal antibodies of Yersinia enterocolitica in artificially-contaminated pork

Monoclonal antibodies against Yersinia enterocolitica were produced by fusion of NS-1 mouse myeloma cells with spleen cells of ICR mice immunized with heat-killed and heat-killed plus SDS-mercaptoethanol treated forms of Y. enterocolitica ATCC 27729 alone or mixed with Y. enterocolitica MU. The twenty-five MAbs obtained from five fusions were divided into nine groups according to their specificities to different bacterial strains and species, as determined by dot blotting. The first five groups of MAbs were specific only to Y. enterocolitica, but did not recognize all of the isolates tested. MAbs in groups 6 and 7 reacted with all isolates of Y. enterocolitica tested but showed cross-reaction with some Yersinia spp. and Edwardsiella tarda, especially in the case of group 7. MAbs in groups 8 and 9 reacted with all isolates of Y. enterocolitica and Yersinia spp., as well as other Gram-negative bacteria that belong to the family Enterobacteriaceae. These MAbs recognized Y. enterocolitica antigens with apparent molecular weights ranging from 10-43 kDa by Western blotting, and could detect Y. enterocolitica from ∼10³-10⁵ colony forming units (CFUs) by dot blotting. The hybridoma clone YE38 was selected for detection of Y. enterocolitica in pork samples which had been artificially-contaminated by inoculation with Y. enterocolitica ATCC 27729 at concentrations of ∼10⁴-10⁶ CFUs/g and incubation in peptone sorbitol bile broth at 4°C. Samples were collected and applied on a nitrocellulose membrane for dot blotting with trypticase soy and cefsulodin-Irgasan-novobiocin agars. After 48 hr of incubation, the detection limit was ∼10²-10³ CFU/g by dot blotting.