Preparation And In Vitro Study Of IgY Against Dairy Cow Mastitis-causing Staphylococcus Aureus

Dairy cow mastitis is one of the main causes of economic losses in dairy cow industry. Antibiotics are used widely in prevention and treatment of dairy cow mastitis. With the present awareness of the problems associated with antibiotics-resistant and its residue, it is urgent to find an alternative to antibiotics.Chicken egg yolk immunoglobulin (IgY) provides an inexpensive and effective source of antibodies for the passive immunization of animals. It is a promising alternative for the treatment and prevention of bacteria infections, and has shown to be effective against a number of pathogens.The objective of this study was to produce egg yolk immunoglobulin (IgY) against mastitis-causing Staphylococcus aureus (S. aureus) and evaluate its activity. Laying hens were immunized with formalin-killed S. aureus isolated from infected mammary gland. IgY was purified from the water-soluble fraction (WSF) by a combination of several purification techniques including salt precipitations and ultrafiltration. The purity of the IgY finally purified was 94.52 %. Highest titer of specific IgY determined by indirect enzyme-linked immunosorbent assay (ELISA) was 1:25600. Totle IgY and specific IgY content (in yolk) measured by competitive ELISA was 9.56 mg/mL and 1.57 mg/mL, respectively. The inhibiting activity was dose-dependent and the growth of S. aureus growth was evidently inhibited by specific IgY at the concentration of 5 mg/mL. Immunoelectron microscopy revealed specific IgY bound to S. aureus resulting in surface structural alterations. S. aureus phagocytosis by cow polymorphonuclear leucocyte (PMN) and macrophage(MΦ) in blood and milk were both accelerated by specific IgY at concentration of 0.05 mg/mL.The results indicated specific IgY against mastitis-causing S. aureus could inhibit growth of the bacteria and enhance phagocytosis of cow PMN in both milk and blood .The current work suggests specific IgY has potential to be a therapeutic treatment for dairy cows mastitis.