Development Of A Selective Media For Quick Differentiation And Antibiotic Sensitivity Test Of Bovine Mastitis-Causing Bacteria

Bovine mastitis is the most costly disease in the dairy industry. Antibiotic resistance is a prevalent problem in dairy industry due to the continuous and inappropriate use of antibiotics for bovine mastitis control, particularly in developing countries.To develop a quick method for differentiation and antibiotic sensitivity test of Streptococci,Staphylococcus aureus and Escherichia coli from the diseased cows, three selective broth were developed based on the recipe of nutrient broth medium,Baird-parker medium and MacConkey medium.These three new selective broth were named EN,mBP and MQQ.Here we demonstrated that, among 10 species of Gram-positive and Gram-negative bacteria tested, only Streptococci could grow in the EN medium. Following inoculation with 10μl of milk samples and incubation overnight at 37℃, the presence or absence of Streptococci in milk could be identified based on the change of turbidity and color of the medium. The medium had some inhibitory effects on activities of antibiotics commonly used for treating bovine mastitis, which could be avoided by adjusting the concentrations of the antibiotics for quick antibiotic sensitivity test using EN medium. By inoculating the medium containing adjusted minimal inhibitory concentrations of antibiotics with milk samples,a quick antibiotic sensitivity test was developed and the results could be obtained following overnight incubation.We also demonstrated that, among 11 species of Gram-positive and Gram-negative bacteria tested, only Staphylococcus aureus could grow in the mBP medium. Following inoculation with 10μl of milk samples and incubation overnight at 37℃, the presence or absence of S. aureus in milk could be identified based on the turbidity and color...