Antibiotic Residues in Milk from Juja and Githurai Markets in Kenya by Liquid Chromatography-Tandem Mass Spectrometry

The use of antibiotics in livestock production can potentially generate drug residues in animal products, leading to adverse health effects for consumers. This study was carried out to assess the presence and quantify the levels of antibiotic residues in milk sold in Juja and Githurai markets in Kenya. A total of 65 milk samples, comprising raw milk purchased from shops (32 samples), milk purchased from automated vending machines (23 samples) and packet milk (10 samples) were analyzed for the presence of amoxicillin, cloxacillin, tetracycline, sulfamethoxazole and trimethoprim residues. A single aqueous extraction was performed and the extracts were analyzed using liquid chromatography-tandem mass spectrometry. The prevalence of antibiotic residues in raw milk samples purchased from shops and milk dispensed from automated vending machines was 46.9% and 26.1%, respectively. No antibiotic residues were detected in packet milk samples. The prevalence of antibiotic residues was higher in milk from Githurai market compared to Juja market (52% vs. 25%, P value = 0.0137). Overall, 10.8% of samples tested positive for at least one antibiotic residue above the maximum residue limits established by the Codex Alimentarius Commission and the European Union, while 20% of samples had detectable antibiotic residues at concentrations below the maximum residue limits. The mean concentrations were 6.7 µg/L, 53.3 µg/L, 30.6 µg/L, 5.0 µg/L and 6.2 µg/L for amoxicillin, cloxacillin, tetracycline, sulfamethoxazole and trimethoprim, respectively. These results suggest frequent occurrence of antibiotic residues in some milk from the selected markets, which may be posing a public health risk to consumers.