Hemagglutination and Hemolysis by Escherichia coli Isolated from Bovine Intramammary Infections

Seventy-six Escherichia coli isolated from bovine intramammary infections were tested for hemagglutination and hemolysis of erythrocytes. Fifty-seven percent of isolates were hemagglutination-positive for bovine erythrocytes compared with 46% that agglutinated guinea pig erythrocytes. Twenty-eight percent of isolates were hemagglutination-positive for erythrocytes from both species. Only 14.5 and 2.6% of isolates were mannose-resistant, hemagglutination-positive for bovine and guinea pig erythrocytes, respectively. Neither duration nor severity of infection from which isolates were obtained differed between isolates that were hemagglutination-positive and hemagglutination-negative. Percentage distribution of hemagglutination-positive isolates did not differ among isolates from infections that originated at calving, during lactation, or the first half of the dry period. Hemagglutination reactions were also not related to in vitro growth in cell-free dry cow secretion. Percent of isolates that caused hemolysis of washed bovine erythrocytes was 2.6% compared to 3.9% for sheep erythrocytes. Hemolysis was not related to hemagglutination. Hemagglutination and hemolysis of erythrocytes did not appear to be virulence factors for E. coli isolated from bovine intramammary infections.