ABSTRACT
In the Compart et al. (2013) study, DG samples had relatively low concentrations of antibiotic residues. Furthermore, 17 of the 20 antibiotic residue concentrations, using the ion-trap MS/MS method, were biologically inactive. Antibiotic residues inhibited bacterial growth in 3 of the 20 samples. Lack of inhibition in all other antibiotic-positive samples (17) was likely due to antibiotic degradation. Penicillin and ampicillin are sensitive to acids and bases during sample preparation and analysis (De Alwis and Heller, 2010). The probability of degradation varies with the nature of the side chain (Stolker and Brinkman, 2005; Botsoglu and Fletouris, 2001). Tetracyclines degrade through epimerization, dehydration and isomerization in strong acids and bases (Anderson et al., 2005; Stolker and Brinkman, 2005; Botsoglu and Fletouris, 2001). Penicillin, erythromycin and tylosin all degrade at a pH 4.0, during ethanol fermentation and render them to be inactive (Aksenova et al., 1984; Brisaert et al., 1996; Islam et al., 1999). Bacitracin, a peptide, transforms to epibacitracin in strong acid (Wan et al., 2006).
