Validation and application of an immunochromatographic test to detect four macrolides and two lincosamides in raw cow milk.

In this study, an immunochromatographic test (using the Charm QUAD2® Test) was used to screen for residual macrolides and lincosamides in raw cow's milk. The validation parameters (selectivity/specificity, detection capability (CCβ), and ruggedness) were in agreement with the requirements of[EC] 2021. The selectivity of the immunochromatographic test was verified by the negative results of microbiological tests. The false-positive rate was 0%. The CCβ values of the immunochromatographic test for various antibiotics in milk were as follows: erythromycin 0.02 mg/kg, spiramycin 0.1 mg/kg, tilmicosin 0.025 mg/kg, tylosin 0.05 mg/kg, lincomycin 0.15 mg/kg, and pirlimycin 0.15 mg/kg. The determined CCβ values were lower than the respective maximum residue limits (MRLs; regulatory limits in Japan) for milk, except for lincomycin (equal to the MRL). The presence of antibiotic groups other than macrolides and lincosamides did not interfere with the specificity of the test. It showed no significant difference in lot-to-lot repeatability. The results obtained by the two researchers showed no significant differences. Finally, the test was applied to milk samples obtained from a tylosin-treated cow. The outcome was positive and in agreement with the results of the chemical analytical and microbiological methods. Therefore, this validated immunochromatographic test is expected to be suitable for routine analysis to ensure milk safety.