[Isolation of an agglutinating anti-E. coli K 88+ serum]

An agglutinating anti-K 88+ serum was obtained through immunizing rabbits with geometrically rising amounts of cell-free K 88 antigenic extraction. Use was made of bacterial suspensions cultured in Minka agar and homogenized at 8000 r. p. m. to remove the K 88 pili. The cell depot was removed by centrifugation at 15 000 r. p. m., and the protein in the supernatant was determined by the method of Kingsey. The titer of the K88 serum was within the 1:320-1:640 range. The specificity and activity of the serum was evaluated by the hemagglutination test, immunoelectrophoresis, and immunodiffusion. The serum is highly specific and yields positive agglutination results with all K 88+ Escherichia coli strains. It does not react with antigen - K 88-negative E. coli organisms as well as with the O antigen of the investigated strains.