IMMUNOCOMPROMISE IN GNOTOBIOTIC PIGS INDUCED BY VEROTOXIN-PRODUCING ESCHERICHIA-COLI (O111 NM)

A verotoxin-producing Escherichia coli serotype O111:NM strain (strain 10049; verotoxin 1 positive) persistently infected experimentally ino culated gnotobiotic pigs, causing attaching-effacing intestinal lesion s and chronic diarrhea. Experiments were performed to determine whethe r persistent infection might be associated with immunocompromise of th e host by this organism. Pigs inoculated with this strain had a signif icant reduction in peripheral blood lymphocytes and lower antibody tit ers to sheep erythrocytes compared with control pigs. Compared with pi gs given a verotoxin-negative pathogenic strain of the same serotype ( O111:NM, strain 2430), pigs inoculated with the verotoxin-positive str ain had lower peripheral lymphocyte counts and proliferative responses to concanavalin A, phytohemagglutinin, and pokeweed mitogens. The res ults of this study suggest that strain 10049 has an immunocompromising effect on gnotobiotic pigs.