Assessment of Penicillin G and Oxytetracycline residues in packed milk sold at distribution outlets in Kampala-Uganda

Abstract

Antibiotics are extensively used for the treatment, prophylaxis and the production of livestock to sustain socioeconomic livelihood of about 250–300 million people worldwide. It’s projected that over 63,151 tons of antibiotics are administered annually to enrich the quality and quantity of milk production. Regrettably, the use of these antimicrobial agents in African countries remains largely unregulated which may precipitate drug resistance and potential residues generation in the tissues of treated animals. FAO/WHO have set standards for maximum antibiotic residue limits in milk that should not be exceeded at 4 mcg/L for penicillin G and 100 mcg/L for oxytetracycline. Failure to adhere to proper withdrawal periods following treatment may result into public health hazards such as penicillin allergic reactions estimated at 4-11%, carcinogenicity, mutagenicity, teratogenicity estimated to be 18%, and high risk of developing secondary tooth discoloration among children. The main aim of the study was to assess levels of penicillin G and oxytetracycline residues in packed milk sold at distribution outlets in Kampala-Uganda. The samples were analyzed by LC–MS/MS. The linearity range was in the concentration range of 10-160 ppb. The regression equation of Penicillin G and Oxytetracycline concentration over their peak area ratio was found to be y = 0.4102x+13.383 (R2 =0.9992) and y=0.7597x + 3.8351 (0.9945) respectively. The recoveries ranged from 80% to 93.3%. The accuracy was expressed as the recovery that was determined in triplicate by adding blank milk samples (5ml) spiked with the centrifuged antibiotic standards to obtain various concentrations: 50, 100, and 150 ppb. The limit of quantification (LOQ) was calculated to be 52 mcg/kg for oxytetracycline and 2mcg/kg for Penicillin G. The limit of detection (LOD) value was 17.276 mcg/kg for oxytetracycline and 1.5 mcg/kg for penicillin G. Blank determinations were also analyzed to calculate the LOD and LOQ value which were the same. The range for oxytetracycline residue level was 52 μg/kg to 98 μg/kg while penicillin G residue levels were below detectable levels This study showed no detectable residue levels of Penicillin G in all samples and 46.7 % had detectable levels of oxytetracycline in milk sold at distribution outlets in Kampala. The levels were below MRL recommended by Codex Alimentarius Commission, and the European Union, 2007. Therefore, do not violate set food safety standard for human consumption.