Principle of Assay
Beta Lactam + Tetracycline + Streptomycin + Chloramphenicol + Cefalexin Strip Test Kit (A327186) uses a competitive colloidal gold based format. The milk sample (200 µl) is added to a clear plastic reaction vessel, and used to resuspend the lyophilized reagents to a uniform pink color in the bottom of the microtiter wells. The milk is incubated briefly (3 min) to allow the Beta Lactam + Tetracycline + Streptomycin + Chloramphenicol + Cefalexin binding proteins on the gold particles to engage with any antibiotic present in the milk. The test strip is then inserted into the sample well with the arrows pointing downward initiating capillary flow up the strip. Each test strip is imprinted with five test lines and one Control line (C-line) at the top. Any gold particles that are not complexed with antibiotics present in the milk will bind to their respective test line, forming a signal (red line) at that position. If the binding protein on the gold particle has engaged with the Beta Lactam + Tetracycline + Streptomycin + Chloramphenicol + Cefalexin residues present in the milk sample, the gold particle will flow past the test line and reach the C-line. For visual interpretation of the test results, any test line signal intensity that is stronger than the signal at the C-line indicates a negative result. Signal at any test line which is equal or less intense compared to the C-line indicates the presence of the corresponding compound in the milk. The greater the reduction in signal intensity at the test line, the greater the concentration of the respective residue(s) present in the milk.
