Consumer's rising concern on healthy food and environmentally sound production methods has set new technological challenges in food production. Quality management in the food chain to ensure product safety includes the monitoring for potential residues of pesticides, veterinary drugs and other chemical compounds. These residues can be found at different concentration levels in products from animal origin, such as milk or meat. In the case of antibiotics, residues may inhibit starter cultures in the production of yoghurt, cheese and other solid milk products, and affect the quality of these. More importantly, antibiotic residues may have in the long term a potential insidious effect on public health. Antibiotics are vital medicines considered as the ultimate strategy to treat human infections. Their effectiveness is however threatened by extensive and inappropriate use of these, not only in medicine but also in agriculture. In veterinary practice, antibiotics are utilised at therapeutic levels primarily to treat diseases and to prevent infection. They are also used at sub-therapeutic levels to increase feed efficiency, promote growth and prevent disease. Public health consequences from the excessive use of antimicrobials in livestock production include the emergence of resistant bacteria. Antibiotics favour such selection in the digestive tube of the host animal. Moreover, genes responsible for this resistance can migrate from one bacterial flora to another through the alimentary chain, and therefore increase the bacterial resistance. Additionally, bacterium resistant to one antibiotic in particular can potentially develop a multi-resistance profile. Unless new classes of antibiotics are devised or discovered, the increase of bacterial resistance will narrow the list of antibiotics that can ultimately be used for the treatment of infections. The needs to evaluate the safety of selected veterinary drugs residues used in food-producing animals, define acceptable daily intakes for humans, and recommend maximum residue limits have been recognised world-wide by various public authorities. Until now, the analysis or detection of these substances is most commonly performed using microbiological methods and physical-chemical HPLC methods in the post-screening phase. There are disadvantages to that approach as these tests can only be performed in a well-equipped laboratory. Aside from the fact that this approach is costly, there is a tendency to bring the "laboratory to the samples", that is to identify critical points in the production chain and perform the control directly at these points: e.g. production chain management, hazard analysis critical control points. To make that a feasible approach, simple and cheap devices for on-site monitoring of critical parameters are needed. A number of rapid tests with detection sensitivities for most ß-lactam antibiotics in the low ppb (mg/kg) range, are already commercially available for screening residues in various biological fluids such as milk, plasma, and urine. These tests however cannot discriminate among different ß-lactam drugs. Alternative confirmatory methods with equivalent or better detection sensitivity are therefore needed, to confirm the identity or identities of the specific ß-lactams eliciting presumptive positive responses and to determine their residual concentrations.
To meet the need of alternative confirmatory methods and practical instrumentation for on-site monitoring and discrimination of ß-lactam residues in milk, the main objective of this project is to develop and optimise a plug-in detection cartridge supporting a molecularly imprinted polymer assay. This cartridge will consist of a microfabricated column accommodating an optical detection window. Molecularly imprinted polymers (MIPs) in the form of beads will be used as packing materials and recognition elements. Analyte binding will be detected by fluorescence. Different assay formats, labels, and optical detection schemes will be evaluated. The best candidates will be optimised to meet the required assay specificity and sensitivity. Participation of a national reference laboratory in the project will enable field trials of the developed cartridge in real experimental conditions and validation of the analytical method.
The concept of a cartridge supporting a molecularly imprinted polymer (MIA-cartridge) will be demonstrated. State-of-the-art replication techniques in plastics will ultimately be utilised to produce cheap and disposable cartridges. A portable instrumentation will be developed to enable screening tests to be performed at the farm and processing dairy with MIA-cartridge prototypes. Field trials will assess the validity of this analytical system.
This novel analytical instrumentation will be designed and optimised to allow handling by non-chemists in non-laboratory settings. The approach relies on robust molecularly imprinted polymers as the recognition element and has therefore obvious advantages over conventional immunological and biochemical methods in terms of stability (mechanical, chemical, and thermal). The detection of ß-lactam antibiotics in milk has been chosen as a model system to demonstrate the general principle of the system. It is anticipated that the approach can be applied also to other substances needed to be easily monitored in non-laboratory settings.