SURFACE-PROPERTIES OF DIARRHOEAGENIC ESCHERICHIA-COLI ISOLATES

The surface properties of various Escherichia coli isolates associated with diarrhoeal illness were compared by aqueous partitioning between polyethylene glycol (PEG) and Dextran phases. Two well characterised strains of enteropathogenic E. coli (EPEC) were found to be very hydro phobic, based on the critical polymer concentration, EPEC strain E2348 cured of the EPEC adherence factor (EAF) plasmid had much reduced sur face hydrophobicity. Partitioning of a series of diarrhoeagenic E. col i strains demonstrated that the majority of EAF(+) EPEC strains were s ignificantly more hydrophobic than EAF(-) EPEC strains. E. coli strain s defined as enteroaggregative on the basis of hybridisation with a sp ecific DNA probe showed much greater heterogeneity in their partitioni ng behaviour, possibly indicating that the AAF/I pili were not express ed in all strains. The E. coli K-12 strain used as a transformation ho st for adhesion studies had very low surface hydrophobicity but had a detectable negative charge. No alteration in these properties was obse rved when transformed with EPEC and recombinant plasmids known to spec ify adherence to tissue culture cells.