An evaluation of the IDEXX SNAP test for the detection of beta-lactam antibiotics in ex-farm raw milks

The detection of antimicrobial residues in 1004 ex-farm raw milk samples by the IDEXX SNAP β-lactam test and by the Delvotest P, as employed in the Milk Quality Payment Scheme of the Milk Marketing Board for England and Wales, was compared. The repeatability of the SNAP test was assessed by examining three penicillin G standards at each chosen level on each ofthe test occasions. One hundred samples giving positive results in the full MMB Quality Payment Scheme procedure were also examined by the SNAP test and the presence of β-lactams was confirmed by a range of confirmatory tests. In the routine survey of ex-farm milk samples, the SNAP test showed a >98% correlation with the Delvotest P and the presence of β-lactams in the majority of samples was demonstrated by the confirmatory tests. In the evaluation of 100 samples previously identified as positive by the Delvotest P test, the SNAP test showed a ≥95% correlation with the confirmatory tests ; only 2 of 98 positive samples could not be shown to contain penicillinase-sensitive β-lactams. The SNAP test was able to detect β-lactams within 10 minutes and provides a rapid, simple to use test that accurately detects penicillin G in bulked, ex-farm raw milks. The test could be employed, both by the farmer and the dairy to ensure that levels of β-lactams in the milk supply remain below the Maximum Residue Limits currently defined in European Union legislation.