Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/6/2005
Publication Date: 1/15/2006
Citation: Harp, J.A., Waters, T.E., Goff, J.P., Bannerman, D.D., Paape, M.J. 2006. Expression of lympocyte homing and adhesion molecules during intramammary infection of cows with Serratia marcescens or Streptococcus uberis: Correlation with bacterial colonization and clinical signs. Veterinary Immunology and Immunopathology. 109(1-2):13-21. Interpretive Summary: Mastitis is a major problem facing the U.S. dairy industry and is estimated to result in losses to producers of over $1 billion annually. Many different types of bacteria can cause mastitis, and clinical symptoms and recovery of cows from disease may differ depending on the organism causing the infection. In this study, we determined that characteristics of the immune cells in response to infection with two different bacteria were different and were related to the response of the cow to the infection. Understanding how different types of immune cell responses affect the ability of the cow to recover from infection will contribute to the development of strategies to fight bacterial infections causing mastitis and can result in economic benefit to both producers and consumers.
Technical Abstract: Healthy, mid-lactating Holstein cows were infected by intramammary infusion with Serratia marcescens or Streptococcus uberis. Following infection, milk samples were collected from all infused quarters at various time points and body temperatures of the cows were taken. Milk was analyzed for colony forming units (CFU) of bacteria, and somatic cell counts (SCC). Leukocytes were isolated from the milk and analyzed by flow cytometry. Percentages and types of lymphocytes were determined as well as expression of CD62L and CD11a adhesion molecules on these cells. We found that the percentage of lymphocytes expressing either CD62L or CD11a showed a marked increase 12 h post infection (PI) with S. marcescens that was not seen in cows infected with S. uberis. CFU of bacteria isolated from mammary glands of S. marcescens-infected cows dropped precipitously 24 h PI but continued at high levels in S. uberis-infected cows. Body temperatures became elevated in both groups of cows, peaking at 24 h PI in S. marcescens-infected cows and dropping thereafter. In contrast, temperatures of S. uberis-infected cows continued to rise and were still elevated 96 h PI. SCC began falling in S. marcescens-infected cows 48 h PI but continued to increase in S. uberis-infected cows. We hypothesize that increased percentages of lymphocytes expressing CD62L and CD11a in the mammary secretions of cows infected with s. marcescens but not S. uberis may play a role in the clearance of bacteria and concomitant decrease in somatic cell counts and body temperature seen in the S. marcescens-infected cows.