Study On The Microorganism Inhibitory Test Reagent For Antibiotic Residues In Milk

Two Target bacteria, a Geobacillus stearothermophilus sb. stain(Geobacillus stearothermopHilus CGMCC1.1923T ) and a Streptococcus thermophilus stain(Streptococcus thermopHilus CICC 6038) are selected for antibiotics tests development, among nine standard stains through growth observation, acid producing ability, antibiotics susceptability test, antibiotics susceptible limit test, and comprehensive analysis. Response time, determination limits was the index for parameters (bacteria counts in the test) and formula obtimization. And hardness test, disintegration time and shaking stability test were conducted to ingredient obtimization for the tablet test too.As results, detemined parameters for the tests are: Tube TestⅠ, Geobacillus stearothermophilus sb. 1 ~ 4×108 cfu/ml, pH=7.5 and BCP 0.005%; Tube TestⅡ, Streptococcus thermophilus 1 ~ 4×108cfu/ml, pH=7.0 and BCP 0.005%. And for Tablet testⅠ, Geobacillus stearothermophilus sb. 1 ~ 4×108cfu/tablet, pH= 6.8 ~ 7.0 and BCP 0.05%. Tablet testⅡ, Streptococcus thermophilus 1 ~ 4×108cfu/tablet, pH= 6.8 ~ 7.0 and BCP 0.05%. Detection limit of 9 antibiotics for Geobacillus stearothermophilus sb. tests were mostly close to MRL, Streptococcus thermophilus tests were the second accurate, and the national TTC method indicated the least susceptable. The determination limit of the tablet and tube test forβ-lactamase residue in milk were evaluated too, By adding appropriate concentrations of penicillin G and cephazoline in milk, the detection limit forβ-lactamase was 20 U / ml.