The Modified New Two Plates Test for Detecting Tetracycline, Beta-Lactam, and Sulfonamide Antibiotic Residues in Kidney and Muscle of Cattle Slaughtered in North-East Benin

Abstract

In Benin, veterinary antibiotics are widely used for cattle breeding. This livestock contributes to 57% of the locally produced meat. The aim of this study was to assess the impact of the large use of antibiotics by determining the contamination level with antibiotic residues in bovine meat, in North Benin. Kidney and muscle samples taken from 50 bovine carcasses in the 2 main slaughterhouses of Parakou were analyzed for the presence of antibiotic residues by a screening method modified from the “New Two Plates Test” (NTPT), to identify tetracyclines, sulfonamides, and beta-lactam groups of antibiotics. Thirteen kidney and muscle samples were subjected to liquid chromatography coupled to tandem mass spectrometry analysis for the confirmation of tetracycline and sulfonamide residues. After modified NTPT screening, tetracycline residues were identified in 54% of cattle carcasses while beta-lactam and sulfonamide residues were present, respectively, in 2 and 6% of sampled animals. The LC-MS/MS analysis confirmed the presence in the kidney tissue of oxytetracycline, epi-oxytetracycline, tetracycline, and epi-tetracycline at maximum levels, respectively, of 1380, 350, 190, and 230 μg kg−1. Sulfamethazine residues were confirmed in one of cattle carcass at very high levels of 3900 μg kg−1 in kidney and 2220 μg kg−1 in muscle. Antibiotic residue levels were found above the maximum residue limit applied in the European legislation in 38% of the carcasses subjected to the LC-MS/MS analysis. These high levels of contamination with antibiotic residues are a potential threat for the health of consumers, and are of concern regarding the selection of antibiotic-resistant bacteria in animals and humans.