Isolation and characterization of the non-fimbrial adhesin NFA-4 from uropathogenic Escherichia coli O7:K98:H6.

The non-fimbrial adhesin NFA-4 from uropathogenic Escherichia coli O7:K98:H6 mediates the agglutination of human red cells (RBC), notably of blood group MM. The adhesin can be separated from the bacteria by heat extraction and was purified to homogeneity by ammonium sulphate precipitation and anion exchange chromatography in the presence of 8 M urea. NFA-4 consists of non-covalently linked 28 kDa subunits which tend to form aggregates of an apparent molecular weight in excess of 10(6) Da. The first 23 amino-terminal amino acids were sequenced, and no homology of this region was found with that of the blood group M specific non-fimbrial adhesin of an unrelated uropathogenic E. coli. It has, however, an about 70% homology to the corresponding region of the K88 antigen from animal-pathogenic enterotoxic E. coli. Both polyclonal and monoclonal antibodies against NFA-4 were prepared. One of the monoclonal antibodies strongly inhibits the hemagglutinating activity of both whole bacteria and purified NFA-4.