It has been known for some time that not all pigs are susceptible to infection with K88 E. coli bacteria.

Recently, South Dakota State University (SDSU) researchers have determined how that resistance occurs and have estimated the number of pigs that possess the resistance trait.

The SDSU researchers identified a glycoprotein (protein containing sugar molecules) called IMTGP that is produced in the intestinal lining of some, but not all pigs.

Because K88 E. coli attach to IMTGP, it appears that this glycoprotein allows the bacteria to adhere to intestinal cells and grow there.

Germ-free pigs that had intestinal cells with IMTGP were found to be highly susceptible to K88 E. coli. Pigs that did not have IMTGP in their intestines were resistant to the E. coli bacteria.

Also, the intestines of pigs tha t produced IMTGP were highly colonized with K88 E. coli. But the intestines of pigs that did not produce IMTGP were not.

"This discovery suggests that selective breeding for disease resistance will be feasible once practical tests for detection of IMTGP are developed, or the genes responsible for its production are developed," says David Francis, SDSU lead researcher in the project.

Despite lack of a practical test to identify pigs that produce IMTGP, there is a way to identify pigs resistant K88 E. coli. The bacteria is able to adhere to intestinal cells isolated from some pigs, but not others.

All pigs that produce IMTGP are among those that allow the E. coli bacteria to adhere to intestinal cells. Thus, no IMTGP-producing animals are among the pigs that don't allow this adherence. Pigs that don't allow adherence are therefore resistant to the bacteria.

To prove resistance occurs, SDSU investigators tested intestinal cells from 96 weaned pigs from 24 purebred farms. There was some breed to breed variation, but 49% of the cell specimens from pigs of the Chester White, Duroc, Hampshire and Yorkshire breeds failed to support adherence of the K88 E. coli. This suggests that half or more of the pigs in the sample, and perhaps swine population, are disease resistant.

Identification of resistant animals, and breeding for the resistant trait, may become practical in the future. Also, with greater understanding of how IMTGP promotes bacterial colonization, it may be possible to develop a specific, non-antibiotic therapy to block the attachment of K88 E. coli to intestinal cells of susceptible piglets.

Researchers: David Francis, Alan Erickson, Philippe Grange and Diane Baker, South Dakota State University, Brookings, SD. Phone Francis at (605) 688-5680.