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

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.

Keywords:

• microbiological screening method
• validation
• animal feed
• antibiotics
• collaborative study
• spiramycin
• virginiamycin
• tylosin
• zinc bacitracin
• avoparcin

Acknowledgements

The authors would like to acknowledge the financial support of the European Commission, DG RTD, Fifth Framework Programme, Competitive and Sustainable Growth (GROWTH) Programme, Generic Activity three: Measurements and Testing, Contract No. G6RD-CT-2000-00413 (SIMBAG-FEED), titled ‘Screening and Identification Methods for Official Control of Banned Antibiotics and Growth Promoters in Feedingstuffs’. The authors would like to thank Gerard Kramer and his colleagues from the JRC-IRMM for the preparation of the blank materials, and Christoph von Holst, Gisele Gizzi, and Ursula Vincent from the JRC-IRMM for their advice about the design and interpretation of the results of the collaborative study. Furthermore, they would like to thank the following collaborating laboratories for their cooperation and participation in this study: AGES, Austria; ALP, Switzerland, CCL, the Netherlands; Central Control and Test Institute of Agriculture, Slovakia; Danish Plant Directory, Denmark; DGCCRF-L35, France; Fed. Voedingslab., Belgium; Istit. Zoo. Sper. Lombardia E. Romagna r. Bromat. Feeds Lab, Italy; Lab. Del Farmaco e Analysi Residui–CRNZB-Inst. Zoo. Sper. Sardegna, Italy; Forschunganstalt LUFA Rostock der LMS, Germany; LAREAL, France; LUFA Augustenberg, Germany; LUFA Dep. Microbiology, Germany; LUFA Leipzig, Germany; LUFA-ITL, Germany; Staatl. Tierarstl. Untersuchungsamt Aulendorf- Diagnostikzentrum, Germany; and State Vet. Med. Diagnostic Centre, Latvia.