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(1999) Suitability of the charm HVS and a microbiological multiplate system for detection of residues in raw milk at EU maximum residue levels, Veterinary Quarterly, 21:1, 21-27, DOI: 10.1080DOI: 10. /01652176.1999 Accepted for publication: October 13, 1998 SUMMARY In this paper we assessed the suitability of the Charm HVS and a newly developed microbiological multiplate system as post-screening tests to confirm the presence of residues in raw milk at or near the maximum permissible residue level (MRL). The multiplate system is composed of Bacillus stearothermophilus var. calidolactis plate at pH 8.0 for detection of beta-lactam antibiotics and tylosin, Bacillus cereus plate at pH 6.0 for detection of tetracyclines, Micrococcus luteus plate at pH 8.0 for detection of macrolides, Bacillus subtilis BGA plate at pH 8.0 for detection of aminoglycosides, trimethoprim-containing plate seeded with B. subtilis BGA at pH 7.0 for detection of sulphonamides, Escherichia coli plate at pH 6.0 for detection of quinolone and polymyxin, and Staphylococcus epidermidis plate at pH 6.0 for detection of novobiocin. For each test plate an action level is proposed in such a way that residues can be detected in raw bulk tank milk at levels near or below the established EU MRLs of beta-lactam antibiotics, tetracyclines, aminoglycosides, macrolides, sulphonamides, colistin, and quinolones. The Charm HVS test used to confirm the presence of tetracycline and macrolide residues gave false-positive results near the EU MRLs. The multiplate system gave valid results. Based on data for raw bulk tank milk samples and the proposed action level for each test plate for suspected samples, we demonstrated that the multiplate system is a reliable postscreening method that can be performed easily and cheaply in microbiological laboratories.

Navrátilová P., Borkovcová I., Dračková M., Janštová B., Vorlová L. (2009): Occurrence of tet-racycline, chlortetracycline, and oxytetracycline residues in raw cow's milk. Czech J. Food, Sci., 27: 379-385. The objective of this study was the detection of tetracycline, chlortetracycline and oxytetracycline residues in raw cow's milk. When analysing bulk milk (n = 57) and tanker trailer'a (n = 113) samples, two methods were used simultaneously: a specific rapid test Milk Tetrasensor Kit and high performance liquid chromatography (HPLC) with ultraviolet detection and isocratic elution. For HPLC analysis, Breeze (Waters, USA), a liquid chromatographic system, was used. The samples underwent solid phase extraction before the HPLC analysis. The Nova Pack C8 column (3.9 × 150 mm, 4 μm, Waters) and mobile phase (0.8 ml/min) consisting of acetonitrile, methanol, and 0.05 mol/l of oxalic acid in a 13:13:74 ratio were used. None of the samples analysed with the use of the specific rapid test displayed the presence of tetracycline antibiotics. In all of the samples analysed by means of HPLC, low concentrations of tetracycline antibiotics residues were detected. None of the samples displayed the presence of chlortetracycline. All of the analysed samples displayed residues of tetracycline. Oxytetracycline residues were detected only in 50.6% of analysed samples.

No abstract

A microbiological screening method (three-plate) for the detection of the antimicrobial growth promoters tylosin, spiramycin, virginiamycin, zinc bacitracin, and avoparcin in animal feed has been developed and validated successfully. A collaborative study involving 18 laboratories receiving 172 samples was carried out to verify the performance characteristics. The detection level for tylosin/virginiamycin/spiramycin, expressed in microbiological activity, was 1 mg kg(-1) (false-positives, 2%; false-negatives, 3, 0, and 6%, respectively). Avoparcin could be detected at 1 mg kg(-1) in feed in general (false-positives, 2%; false-negatives, 0%). However, in calf feed the sensitivity was lower. The percentages of false-negatives were found to be 12%, 7%, and 0% at 1, 3, and 5 mg kg(-1), respectively (false-positives, 4%). The limit of detection for zinc bacitracin was 3-5 mg kg(-1) (false-positives, 5-10%; false-negatives, 77% at 1 mg kg(-1), 45% at 2 mg kg(-1), 12% at 3 mg kg(-1), and 4% at 5 mg kg(-1)). The method allowed for a distinction to be made between the groups of antibiotics: avoparcin/zinc bacitracin versus tylosin/virginiamycin/spiramycin. This definitely gives added value to the method in the framework of a follow-up of positive screening results by post-screening and confirmatory analysis.