Association of hemolysin production, hemagglutination of human erythrocytes, and virulence for chicken embryos of extraintestinal Escherichia coli isolates

Abstract

142 strains of Escherichia coli isolated from extraintestinal infections were examined for colicin V (ColV) and hemolysin (Hly) production. For comparison, 20 strains isolated from the feces of normal individuals and 12 enteropathogenic strains of E. coli were tested for these properties. Thirty-five to 59% of extraintestinal isolates were Hly+, but only one fecal strain was Hly+. Colicin V biosynthesis was found for 12% of blood culture isolates, 7% of urine culture isolates, and 16% of the strains from other extraintestinal infections. None of the fecal isolates was ColV+. Selected strains were tested for virulence in 13-day-old chicken embryos; these same strains were tested for their ability to hemagglutinate chicken or human erythrocytes. Of 22 extraintestinal isolates, 13 (59%) killed ≥60% of the embryos within 72 h. Only 1 or 8 normal fecal isolates and 2 of 3 enteropathogenic strains tested were virulent. About 80% of the virulent strains were Hly+. The most striking finding, however, was the hemagglutination of human erythrocytes by virulent extraintestinal isolates. It seems possible that the heamgglutination property reflects a specific common adherence factor.