Residue Plex

Residue Plex is a Flow Cytometric Affinity assay (FCAA). It uses monoclonal and polyclonal antibodies and natural capture agents fixed on distinct sized microspheres (see Fig. Below) for binding antibiotics.

Discrimination of the individual microspheres is arranged by different internal fluorescent intensities, which lead to multiple analytic results per sample.

With flow cytometry not only fluorescent intensities of microspheres, but also small size variations can be distinguished. In the Plex assay technology, this combination of bead sizes and fluorescent intensities offers the possibility to detect tens of bead variants. This allows the simultaneous detection of many antibiotic families each containing multiple individual antibiotics.

Residue Plex: Natural capture agents, not Antibodies

Antibiotics exert their effects through inhibition of the activity of cell components essential for the homeostasis of the affected bacteria. The receptive component can be any bacterial functional macromolecule.

In a test system, natural capture agents are by far favoured over artificially induced antibodies against small haptens as they are more selective, specific and have higher affinities for the targeted analytes.

They outperform the best antibody, as they react by definition with pharmacological active substances of interest including their active metabolites.

Typical drawbacks of antibodies as non-specific binding and limited cross-reactivity with certain constituents of an antibiotic family are not the case with natural binders.

Universal and simple sample preparation

Residue Plex assays have a single sample clean-up process for all antibiotic tests. And it is much simpler than solid-phase extraction (SPE), as shown in the figure below.

Ability to detect all antibiotic families

Residue Plex already detects three of the main families of antibiotics, including (fluoro)quinolones, which cannot be detected by traditional microbial growth inhibition plate tests.

But more than that, because Residue Plex relies on natural capture agents rather than on antibodies for analyte capture, the assay technology will detect any target antibiotic. And remember, the bead/size combination allows for detection of tens of analytes simultaneously!

So in practice, unlike other affinity tests, there is virtually no limit to the number of antibiotics that can be detected from one sample in one run and in one test.

Unique Tetracycline meat drip test

Residue Tetra-Plex has been validated for the detection of tetracyclines directly from meat drip samples using a 'dilute and shoot' method. This means that the tetracycline test can be carried out with minimal sample preparation while retaining the required sensitivity.

Flexible assay format

RnAssays flexible approach to assay design and production, together with the underlying robustness and simplicity of the bead-based flow cytometry, means that multiplex assays can be tailored to the needs of a specific laboratory. Whether you need to test for zoonoses, animal diseases, residues or combinations of all three groups, RnAssays will be pleased to give careful consideration to your requirements.

Back to the page of Tests for Antibiotic Residues.