An Independent Laboratory Verification of an Antibiotic Assay for the Rapid Detection of β-lactam and Tetracycline Residues in Raw Milk

Introduction: The BetaStar^® Combo 3.0 is a rapid detection assay for both β-lactam and tetracycline antibiotic residues in raw milk.  The test utilizes binding reagents linked to gold particles to bind to antibiotic residues in milk during a three minute incubation period.  After incubation the particles are transferred onto an immunochromatographic medium where the results are interpreted either visually or using an automated reader.  The test employs a three line detection system, to verify the presence of tetracyclines, β-lactams and an internal control to ensure the validity of the test. 

Purpose: The purpose of this independent evaluation was to verify the detection of select antibiotic residues in low concentrations in raw, co-mingled cow’s milk by the antibiotic assay.

Methods: During the evaluation, 16 antibiotic residues, including 7 Penicillins (β-lactams), 6 Cefalosporins (β-lactams),) and 3 Tetracyclines, were analyzed using 3 different lots of the assay. Two operators analyzed each antibiotic twice over a 10 day test period to result in a total of 10 analyses per antibiotic. Findings were interpreted visually by each operator and using the Reveal^®AccuScan III palm reader.  

Results: For each of the 16 antibiotic residues analyzed using the new method, all 10 test portions were correctly identified using the palm reader or visually by one of the two operators. No visual false negative or false positive results were reported using any of the three test lots. The palm reader reported two false positives for tetracycline. A false positive was reported for lot 2 using Cloxacillin and lot 3 using Cefazolin.

Significance: This new method demonstrated reliability as a rapid, easy to use method to detect closer to safe levels for penicillin, cloxacillin, ceftiofur and cephapirin than other rapid method tests in raw, comingled cow’s milk.