Evaluation of Tetracycline and Enrofloxacin Residues in Bovine Milk in Tehran Utilizing ELISA and HPLC Methods

Milk is regarded as one of the most sources of nutrition in the world and has a high value for individual's health. Milk is consumed by sensitive groups including pregnant women, older adults, and children. Therefore, the significance of antibiotic on human health makes it crucial to monitor their existence in food. This investigation aims to evaluate enrofloxacin and tetracycline in the raw and pasteurized milk in Tehran.

In this cross-sectional study, 112 raw and 112 pasteurized milks were accumulated in spring and winter from six reputable brands and traditional dairy stores in Tehran from December 2021 until May 2022 for six months, and antibiotic residues were examined by Immunosorbent Assay and High-Performance Liquid Chromatography techniques.

The findings indicated that the prevalence of tetracycline in raw and pasteurized milk was 41.07 and 26.78% in spring and 85.71 and 35.71% in winter, respectively. The median concentration of tetracycline was 33.27 and 22.65 ppb in spring and 55.81 and 21.91 ppb in winter, respectively. The prevalence of enrofloxacin in raw milk and pasteurized milk samples were 33.92 and 14.28% in spring and 64.28 and 32.14% in winter, respectively. The median concentrations of enrofloxacin were 9.13 and 9.38 ppb in spring and 10.57 and 11.23 ppb in winter, respectively. The raw and pasteurized milk samples collected in winter had higher percentage of antibiotic residue in terms of enrofloxacin than samples collected in spring (p<0.05). Furthermore, the quantity of tetracycline antibiotic in raw milk was significantly higher in winter than in spring (p=0.002). However, the pasteurized milk fails to have significant difference between two seasons. The finding showed the tetracycline and enrofloxacin in all samples were less than 100 ppb (standard limit), and there is no significant difference with the standard limit.

Based on the obtained results, monitoring the antibiotic residues in milk, controlling and minimizing these residues for human health are regarded crucial.