Suitability of the Charm HVS and a microbiological multiplate system for detection of residues in raw milk at EU maximum residue levels

In this paper we assessed the suitability of the Charm HVS and a newly deve loped microbiological multiplate system as post-screening tests to confirm the presence of residues in raw milk at or near the maximum permissible res idue level (MRL). The multiplate system is composed of Bacillus stearothermophilus var. calid olactis plate at pH 8.0 for detection of beta-lactam antibiotics and tylosi n, Bacillus cel ens plate at pH 6.0 for detection of tetracyclines, Microco ccus lutens plate at pH 8.0 for detection of macrolides, Bacillus subtilis EGA plate at pH 8.0 for detection of aminoglycosides, trimethoprim-containi ng plate seeded with B. subtilis EGA at pH 7.0 for detection of sulphonamid es, Escherichia coli plate at pH 6.0 for detection of quinolone and polymyx in, and Staphylococcus epidermis plate at pH 6.0 for detection of novobioci n, For each test plate an action level is proposed in such a way that resid ues can be detected in raw bulk tank milk at levels near or below the estab lished EU MRLs of beta-lactam antibiotics, tetracyclines, aminoglycosides, macrolides, sulphonamides, colistin, and quinolones. The Charm HVS test use d to confirm the presence of tetracycline and macrolide residues gave false -positive results near the EU MRLs, The multiplate system gave valid result s. Based on data for raw bulk tank milk samples and the proposed action lev el for each test plate for suspected samples, we demonstrated that the mult iplate system is a reliable postscreening method that can be performed easi ly and cheaply in microbiological laboratories.