Relative cell surface hydrophobicity of Escherichia coli strains with various recognized fimbrial antigens and without recognized fimbriae.

Bacterial surface hydrophobicity as well as mannose-sensitive haemagglutinating (MSHA) and mannose-resistant haemagglutinating (MRHA) activities were studied in Escherichia coli strains with and without recognized fimbrial antigens grown under different conditions. Relative bacterial surface hydrophobicity was measured by the salt aggregation test. Four kinds of bacterial aggregations depending on fimbrial antigens were observed: bacteria with CFA/I, CFA/II, CFA/III and K88 aggregated in a particulated form, bacteria with type 1 pilus in a granular form, and bacteria with K99 in a tiny granular form. Some strains, mainly when grown under non-optimal conditions at 18 degrees C or when heated at 80 degrees C, aggregated in a non-typical filamentous form. Among MRHA- MSHA+ (type 1 pilus positive), two classes of bacteria were detected: hydrophobic bacteria aggregating in 0.2-0.4 M ammonium sulphate, and non-hydrophobic bacteria aggregating in 2.0 to 1.6 M ammonium sulphate. The hydrophobicity levels in strains possessing different recognized fimbrial antigens, when grown under optimal conditions to express fimbriae and their typical haemagglutination pattern, were of a decreasing order, viz. CFA/III = CFA/I greater than CFA/II greater than MRHA-MSHA+ hydrophobic = MRHA+ greater than P987 greater than K99-F41 = K88 greater than MRHA- MSHA+ non-hydrophobic greater than MRHA- MSHA- without recognized fimbriae.