Validation of the Explorer^® 2.0 test coupled to e-Reader^® for the screening of antimicrobials in muscle from different animal species

Abstract

The Explorer^® 2.0 tube test is a microbial inhibition test for the screening of antimicrobial residues in food samples. The new e-Reader^® device coupled to Explorer^® 2.0 operates by incubation at a selected temperature, determination of the endpoint of the assay and interpretation to generate results. This system was validated for muscle samples according to the European Commission Decision 2002/657/EC. Sensitivity towards 25 substances from several groups of antimicrobials was investigated in a first step. Detection capabilities for six substances representing the six major antimicrobial groups were also determined in bovine muscle. The detection capabilities for amoxicillin (10 µg l⁻¹), cefalexin (200 µg l⁻¹), doxycyclin (100 µg l⁻¹), sulfamethazine (100 µg l⁻¹), tylosin (100 µg l⁻¹) and neomycin (200 µg l⁻¹) were in all cases at or below the maximum residue limit (MRL). Specificity and applicability of the test were demonstrated with muscle samples from four animal species (bovine, porcine, ovine and poultry) and results were found to be satisfactory. Ruggedness was evaluated on negative and spiked samples with sulfamethazine as a representative antimicrobial. Neither false-positives nor false-negatives were detected when varying the sample volume, the time of pre-incubation, the temperature of incubation and the batch of the test. These results prove that Explorer^® 2.0 coupled to e-Reader^® is a valuable tool for the screening of a broad range of antimicrobials in muscle. This new methodology simplifies the analysis and increases the accuracy of interpretation of the test results since the endpoint of the assay is automatically determined and results are interpreted objectively.

Keywords:

• screening
• antimicrobial residues
• muscle
• method
• test
• microbiological
• antibiotic
• validation

Acknowledgements

The authors would like to thank Inma Domingo and Cristina Lizama for technical assistance, and Elena Dominguez for reviewing the manuscript.