Use of a hemadsorption technique to evaluate the stability of the hemagglutination reaction of Escherichia coli cultures possessing human colonization factor antigens

Abstract

Two strains of Escherichia coli, producing different colonization factor antigens (CFA), were monitored for the population density of CFA-producing bacteria after repeated subculture. The production of CFA was estimated by flooding agar plates containing isolated colonies with suspensions of human or bovine erythrocytes. The erythrocytes were suspended in a low-ionic-strength buffer and were fixed to CFA-positive colonies with a 1.0% tannic acid solution. Strain H-10407, possessing CFA/I fimbriae, showed a rapid loss of the hemagglutinin when subcultured, whereas strain CL-9699, producing CFA/II, was very stable. By using the hemadsorption assay, we could rapidly and easily distinguish CFApositive colonies from the CFA-negative variants. A survey of additional E. coli strains demonstrated the utility and specificity of the hemadsorption technique used.

Indications that the erythrocyte receptor involved in enterotoxigenic Escherichia coli attachment is a sialoglycoconjugate

“…RBC preparation. Human citrated type A+ blood was purchased from Community Blood and Plasma Service, Folcroft, Pa., and processed as previously described (21). For determination of the effect of the selected reagents on RBC receptor reactivity, a suspension containing 1.2 x 109 RBCs per ml was prepared in the diluent required by the respective reagents.…”

Isopycnic separation of Escherichia coli cultures possessing colonization factor antigen I

“…The number of MRHA bacteria in each fraction was determined by HAd assay (11). Basically, a sample from each fraction was serially diluted, plated on Casamino Acids agar, and incubated for 48 h at 37°C.…”