Effect of cephapirin and mecillinam on the phagocytic and respiratory burst activity of neutrophil leukocytes isolated from bovine blood

Antimicrobial therapy is the most commonly used treatment of bacterial infe ctions in dairy cows, Polymorphonuclear neutrophil leukocytes (PMN) play an important role in the first line defence against invading bacteria and it is important that the function of PMN is not compromised by antibiotics. We investigated the in vitro effect of cephapirin, a first generation cephalo sporin, and mecillinam, an amidinopenicillin with activity against mainly G ramnegative bacteria, on phagocytosis and respiratory burst activity of PMN isolated from bovine blood, After in vitro incubation of PMN with differen t concentrations of the antibiotics, phagocytosis was evaluated by flow cyt ometry and respiratory burst activity was evaluated by registration of chem iluminescence (CL) with a luminometer, None of the investigated concentrati ons of cephapirin and mecillinam had an effect in vitro on phagocytosis of Escherichia coli by PMN, At high concentrations (100 and 1000 mu g/mL), cep hapirin and mecillinam reduced the respiratory burst activity of PMN. Part of these suppressive effects could be ascribed to oxidant scavenging, Inhib itory effects of cephapirin were stronger than mecillinam. In conclusion, c ephapirin and mecillinam did not seem to affect antibacterial activity of P MN isolated from bovine blood in vitro at therapeutic concentrations.