Screening methods for the detection of antibiotic residues in slaughter animals: comparison of the European Union Four-Plate Test, the Nouws Antibiotic Test and the Premi®Test (applied to muscle and kidney).

Microbial growth inhibition tests are widely used as the primary screening approach for the detection of antibiotic residues in slaughter animals. In this study we evaluated and compared the performance of the European Union Four-Plate Test (EU4pt), the Nouws Antibiotic Test (NAT), and a commercial ampoule test, the PremiTest (applied to both muscle and kidney), by parallel analysis of 735 slaughter animals. The EU4pt only showed significant inhibition with two muscle samples containing 305 µg kg(-1) doxycycline and 648 µg kg(-1) tulathromycin, while an maximum residue limit (MRL) violation of 1100 µg kg(-1) sulfamethazine remained unnoticed. PremiTest-muscle only detected the sulfamethazine containing sample, all other (1.1%) suspect samples appeared false-positive results. The same test applied to kidney yielded 4.1% suspect samples, while the NAT screening (based on analysis of renal pelvis fluid) showed 4.9% suspect results. The vast majority of these samples contained tetracycline and/or aminoglycoside residues. PremiTest-kidney appeared to be more sensitive to aminoglycosides than the NAT screening, which failed to detect an MRL violation of 870 µg kg(-1) gentamicin in kidney. Detection of less than MRL levels of tetracycline residues by the NAT proved its suitability for this residue group. Whether PremiTest is sufficiently sensitive for accurate tetracycline detection in kidney remains doubtful, although changing over to kidney definitely improved the suitability of PremiTest for the detection of residues in slaughter animals.

Collaborative study of a microbiological screening method (three-plate) for the banned antimicrobial growth promotors tylosin, virginiamycin, spiramycin, zinc bacitracin and avoparcin in animal feed.

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.

[The New Dutch Kidney Test. II. Sensitivity of the test system]. / De Nieuwe Nederlandse Niertest. II. De gevoeligheid van het testsysteem.

When the in vitro sensitivity of the New Netherlands Kidney Test (NNKT) is compared with that of the test plates of the current Netherlands Kidney Test (NKT) and the EEC four-plate system (ECT), this shows that it occupies a middle position with regard to aminoglycosides, macrolides and tetracyclines. The test plate of the NNKT is more sensitive to sulphonamides. Experimental qualitative and quantitative studies in slaughtered pigs showed that the New Netherlands Kidney Test was equally sensitive or more so in detecting residues of sulphonamides, chloramphenicol, tetracyclines, aminoglycosides and penicillin derivatives than the ECT system for meat. In addition to the simplicity of the current Netherlands Kidney Test, the New Netherlands Kidney Test also shows the broad-spectrum sensitivity of the ECT system. When tolerance standard of nitrofurans or chloramphenicol respectively is 1 or 10 ppb, the New Netherlands Kidney Test will fail.