Research on optimization of the enrichment broth of Staphylococcus aureus

In order to develop a selective growth solution for Staphylococcus aureus, using 7.5% sodium chloride broth as an initial broth with selective inhibition against Gram-negative bacteria and non-Staphylococcal strains as the base medium, the growth promotion ability of amino acids, sodium pyruvate and mannitol on S. aureus was investigated, and the optimal medium formula was determined by orthogonal tests. Four standard strains of S. aureus from different sources were treated with the optimized medium and the original base medium, and the effect of increasing bacteria and inhibiting Escherichia coli were compared. The results showed that the optimal medium was supplemented with L-alanine 1.0 g/L, mannitol 6.0 g/L and sodium pyruvate 1.2 g/L on the basis of base medium. After the optimization, the turbidity of the strains increased and the number of colonies transferred to Baird-Parker were improved. The OD_{550 nm} value of the strain increased by 0.28-0.34, and the number of colonies after the transfer to Baird-Parker also increased by 10-100 times. While promoting the growth of target bacteria, the inhibition of E. coli was not affected, which indicated that the culture medium had good selectivity.