Development of a test kit for β-lactam antibiotic residues in milk

We used β-lactam antibiotic residues in milk as the target to develop a rapid detection kit. Based on sensitivity of Bacillus stearothermophilus 10208 to acid and β-lactam antibiotics, growth conditions were optimized and a test kit that could show a color reaction within 2.5 h was developed. The results of the single-factor experiment showed that when the inoculum was 5%, initial growth pH was 8.0, culture temperature was 55℃, and the quantity of peptone was 0.50%, the logarithm values of growth for the bacterium were 2.9, 7.5, 7.3, and 5.8, respectively. The results of an orthogonal test showed that when a nutrient broth containing 0.50% peptone was added and the mixture was inoculated with 5% seed broth and incubated for 24 h at 65℃, the logarithm value of growth for the bacterium was 7.6. This optimized test kit could be used to detect residual β-lactam antibiotics in milk within 2.5 h. The parameters were as follows: reaction volume, 0.5 mL; agar, 1.5%; bromocresol purple, 0.01 g/L; total BS 10208 cell number, 1.30 × 108 cfu, and optimum reaction temperature, 65℃. The detection limit on penicillin sodium was 2~4 µg/L. The test kit could also detect residual tetracyclines, sulfonamides, macrolides, aminoglycosides, and other antibiotics in milk. ©, 2014, South China University of Technology. All right reserved.