Escherichia coli Mastitis in the Dairy Bovine

Diagnosis techniques and treatments for Escherichia coli mastitis in the dairy bovine were evaluated in two experiments. The first experiment evaluated eosin methylene blue agar as a method of distinguishing E.coli from other gram-negative mastitis pathogens. Escherichia coli will usually produce a green metallic sheen on eosin methylene blue agar. One hundred and twenty-nine milk samples or gram-negative isolates from milk samples were used to compare eosin methylene blue agar to a commercial biochemical test strip (the accepted standard). There was an intermethod agreement of 96.9% and a k-value of 93.7% indicating excellent agreement beyond chance between test methods. Eosin methylene blue agar is a reliable method for differentiation of E. coli from other gram-negative mastitis pathogens. The second experiment evaluated the efficacy of frequent milk-out as a treatment for E. coli mastitis. Sixteen Holstein dairy cows were divided into 2 blocks and randomly assigned to 1 of 4 treatment groups: 1) non-infected, not frequently milked-out, i.e. not treated (NI-NT), 2) experimentally infected with E. coli, not treated (EC-NT), 3) non-infected, frequently milked-out (NI-FMO), and 4) experimentally infected with E. coli, frequently milked-out (EC-FMO). Hours to bacterial, clinical and systemic cure were not different between the EC-NT and EC-FMO treatment groups. Serum a-lactalbumin concentrations were evaluated between treatment groups as a measure of udder health. Serum a-lactalbumin concentrations were higher in cows in the EC-NT treatment group than cows in the NI-NT, NI-FMO and EC-FMO treatment groups at 12 hours post-experimental challenge. Serum a-lactalbumin concentrations were higher in cows in the NI-FMO treatment group than in cows in the NI-NT, EC-NT and EC-FMO treatment groups at 36 hours post-experimental challenge. Results from this study do not support frequent milk-out as a treatment for E. coli mastitis.