Biofilm Identification And Immunogenicity Study Of Staphylococcus Aureus Induced Mastitis In Dairy Cows

Bovine mastitis caused by Staphylococcus aureus is one of the common diseases that lead to great economic losses in dairy industry. Biofilm formation, which can enhance the drug resistance, is an important factor causing Staphylococcus aureus infections. This kind of phenomenon present in food、health and other social areas.In this study,79milk, samples from a pasture in Inner Mongolia were used to isolate the bacteria and susceptibility testing were conducted to screen the best drug for bovine mastitis. The strongest biofilm formation strain screened by qualitative and quantitative analysis of biofilm, together with SEM observation and API-Staph, was incubated in TSB medium containing1%glucose for5days and then polysaccharide was extracted by enzyme hydrolysis combined with chromatographic column. The content of polysaccharide was determined by phenol sulfuric acid method. At last, the conjugates mixed with purified polysaccharide and cellulose binding protein FnBPA-D were used to immunize mice and the serum antibody titers were evaluated by ELISA.The results show that48bacterial strains were obtained, including22Escherichia Coli,17Staphylococcus,7Streptococcus, and2Bacillus subtilis, account for45.8%,35.4%,14.6%and4.17%respectively. Susceptibility testing indicated that the most three kinds of bacterium were sensitive to Ciprofloxacin, Levofloxacin and Cefotaxime.The polysaccharide purity of the strongest biofilm formation Staphylococcus aureus strain was9.42%, and the refined polysaccharide purity was64.68%.The content of nucleic acid and protein were0.0286mg/mL、0.009mg/mL respectively. Serum antibody titers showed that antibody only could be induced by the conjugates mixed with purified polysaccharide and cellulose binding protein FnBPA-D and the higest antibody titer was1:12800. These indicated that conjugates has a good immunogenicity and can stimulate an immuneresponse in mice.