Thin-layer chromatography—direct bioautography as an alternative method for screening of antibiotic residues in milk: A comparative study

The presence of pharmaceutical residues in food products of animal origin is mainly caused by widespread use of antibiotics in livestock and can lead to undesired effects on consumer health or/and economic losses. Residue monitoring is usually performed using instrumental methods, e.g., liquid chromatography (LC) coupled to mass spectrometry (MS) or UV detection. Low-cost alternatives are bioassays; these are simple and rapid procedures that enable qualitative and semiquantitative analysis of antimicrobial agents. In this study, thin-layer chromatography—direct bioautography (TLC-DB) using Escherichia coli was compared to, widely applied in food analysis, agar-based diffusion bioassays and high-performance liquid chromatography (HPLC) with UV detection. Flumequine and cefacetrile, two antibiotics frequently used in veterinary medicine, were selected as test antimicrobials.