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

One hundred forty-two 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 greater than or equal to 60% of the embryos within 72 h. Only one of eight normal fecal isolates and two of three 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 hemagglutination property reflects a specific common adherence factor.