Study of several factors affecting the agglutinating activity of K99-positive Escherichia coli strains.

The effect of several factors on Escherichia coli K99-plasmid associated agglutination has been studied. The results obtained indicate that Escherichia coli 637 (K99+) mediated red blood cell agglutination is unspecific although the agglutination titres for several erythrocyte species are significantly different. The agglutination is highly stable (at least with sheep red blood cells) to changes in temperature (from 4 degrees C to 37 degrees C), to changes in pH (from 5 to 9) and to the presence or absence of several metallic cations. Treatment of sheep erythrocytes with certain proteolytic enzymes (papain and trypsin) results in a increment in their agglutinability. Also, the extraction of galactose after the removal of sialic acid residues from the oligosaccharides present on the erythrocyte membranes results in a great increment in their agglutinability. On the other hand, only thyroglobulin, mucin, fetuin, and the oligosaccharides extracted from the last two glycoproteins are able to inhibit K99-plasmid mediated sheep red blood cell agglutination.