Abstract

The main aim of this project is to produce polyclonal antibodies directed against theStaphylococcus aureus protein A and their use to appreciate bacteriological analysis of milk quality. In this context, an immunization produce was set up to test and detect in a batch of animals the convenient responder to the injected antigen. Furthermore, to optimize all parameters of retained ELISA test, a cross-table was conceived by using various concentrations of different reagents and has allowed selecting the optimal dilutions as follows: 1) 1/1000 for anti-Staphylococcus aureusprotein A mouse antibodies and 1/2000 for anti-Staphylococcus aureus protein A rabbit antibodies. 2) 1/4000 for anti-Staphylococcus aureus treated by heat mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. 3) 1/2000 for anti-Staphylococcus aureus treated by NaClO mouse antibodies and 1/500 for anti-Staphylococcus aureus protein A rabbit antibodies. The application of optimized ELISA test to search and detect Staphylococcus aureus germs in different samples of milk has shown very satisfying results when compared to those obtained by bacteriological method. Indeed, the sensitiveness and the reproducibility, as well as the possibility to analyze a great number of samples in the same time at a reduced manner make the immunochemical method a best choice of test able to replace recent bacteriological methods.

Key words: Polyclonal antibodies, Staphylococcus aureus, protein A, ELISA, milk.

Abbreviation

Abbreviations: SpA, Staphylococcus aureus protein A; ELISA, Enzyme linked immunosorbent assay; Sc, Staphylococcus aureus treated by heat; Sj,Staphylococcus aureus treated by sodium hypochlorite NaClO; As, Anti-serum;UFC, unit forming colony.