Antibiotics are not permitted in honey. The presence of antibiotic residues can lead to allergic reactions and the development of bacterial resistance.
In several countries some antibiotics may be used in the control of bee diseases, provided they are employed at the right time, using an approved method and at the correct dosage.
It is important, therefore, to have access to rapid and sensitive testing methods that can detect drug residues in honey.
Here we look at rapid screening test kits in comparison to traditional testing methods (LC-MS/MS, HPLC) for determining the presence of the antibiotics chloramphenicol, streptomycin and sulphonamides in honey.
Chloramphenicol
Chloramphenicol is a broad-spectrum antibiotic with excellent anti-bacterial and pharmacokinetic properties. However, its use is associated with the development of aplastic anaemia, a rare but serious blood disorder.
For this reason, it has been banned from use in apiculture in the EU, North America and many other countries.
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a procedure used to confirm the presence of chloramphenicol in honey1.
Preparation involves dissolving the sample in aqueous solution followed by liquid-liquid extraction with organic solvent.
The sample then undergoes serial concentration steps and solid phase extraction (SPE) prior to detection by LC-MS/MS. In contrast, Qflex Kit Chloramphenicol, which does not require the SPE step, offers quick and easy sample preparation and enables rapid sample turnover without loss of sensitivity. The kit is used together with a fully automated system, Biacore Q.
Table 1 shows detection limits (CCa), detection capabilities (CCb) and recovery values for the assay2 compared with an LC-MS/MS method.
Streptomycin
Streptomycin and its derivative, dihydrostreptomycin, are particularly active against aerobic gram-negative bacteria3.
Streptomycin residues are not permitted in European apiculture, but the antibiotic is permitted in the USA for the treatment of American Foulbrood. Withdrawal of its use must take place at least four weeks before the main honey flow.
Available testing methods for streptomycin include: HPLC with post column derivatisation and fluorescence, enzyme immunoassays (EIA) and LC-MS/MS.
Processed honey samples were analysed using
Qflex kits or HPLC and the results are displayed in
Table 34. Qflex Kit Streptomycin requires little more than dilution and pH adjustment of the sample in contrast to HPLC which required elaborate sample preparation.
Sulphonamides
Sulphonamides are a family of broad-spectrum synthetic bacteriostatic antibiotics with activity against most gram-positive and many gram-negative organisms, as well as protozoa.
Sulphathiazole is the only sulphonamide permitted for the treatment of European Foulbrood in the USA. No sulphonamides are permitted in the EU.
Sample preparation for LC-MS/MS and LC-fluorescence-based detection of sulphonamides can be quite tedious, involving hydrolysis, pH adjustment, liquid-liquid extraction, evaporation, SPE and concentration before injection5.
Further, the majority of biological assays for sulphonamides in honey tend to have very limited cross-reactivity within the sulphonamide family, do not reach the required sensitivity for honey analysis and tend to cross-react with N-acetyl metabolites.
Qflex Kit Sulfonamides offers a faster and easier method for the detection of more than 20 sulphonamide compounds in honey. As shown in Table 5, there is good sample recovery from both real and spiked samples. Analysis is rapid, with an injection time of 90 seconds.
Conclusion
Qflex Kits, which include critical reagents and components, are a viable alternative to conventional methods for detecting antibiotics in honey. In addition to being faster and more sensitive than traditional technologies, the assays are user friendly
and simple to run on a Biacore Q system, which automatically provides sample data and standard concentration curves.
Terry McGrath is with Xenosense Ltd, Belfast, Northern Ireland, UK. www.xenosense.co.uk
