PRINCIPLE Based on the inhibition of microbial growth. The kit is presented in a microplate format. Each well contains the agar medium spread with Bacillus tearothermophilus spores plus a pH indicator. When the plate is incubated at 65ºC (into the thermostatic device), the spores germinate and grow, reducing the pH of the medium, which will shift the initial colour from blue (purple) to green-yellow. If milk samples contain an antibiotic concentration higher than the detection limit of the test, the microbial growth and acid production is inhibited. There is no acid production and no colour change is observed.
96 individual tests microtiter plate. Each well contains growth medium spread
with Bacillus stearothermophilus spores.
Adhesive foil to seal the plate.
Optional: An additional plastic frame
STABILITY AND STORAGE The kit components should be stored at 2-8 ºC in darkness. Kit keeps stability for months in optimal storage conditions.
SAFETY INSTRUCTIONS It is recommended a person with laboratory practice to work with this set. Wear suitable working cloths and protect the skin from contacts with reagents. Do not swallow!
It is recommended to apply a negative control (antibiotic-free milk) and a positive control containing a high concentration of antibiotic (for example penicillin G 10 mg/L) for determining the optimal incubation time. If goat samples are analysed, the negative control must be goat´s milk, without inhibitors. It should be used a clean pipette tip for each sample.
This test is extremely sensitive to antibiotics and other antibacterial substances such as detergents and disinfectants. Any contamination with these substances should be prevented.
Plates should be kept closed in the plastic bag to avoid drying out of the wells and stored at 2-8ºC.
Natural inhibitors occurs in milk at low concentration which do not interfere with the test results, but inhibitor substances increase in colostrum, at the end of breeding period and in the case of mastitis. In those cases the results could be altered.
If samples containing preservatives are to be analysed, the time of incubation could be extended for some minutes.