Evaluation of antibiotic resistance, heavy metal levels, and oxidative stress biomarkers in E. coli-contaminated milk in Kurdistan

The production of safe milk in dairy farms is crucial for protecting public health. This study explored microbial contamination, chemical pollutants, and antibiotic resistance in milk from dairy farms in Kurdistan Province. A total of 142 milk samples were analyzed for E. coli contamination, heavy metal concentrations, and oxidative stress biomarkers. E. coli was isolated and tested for antibiotic resistance, while heavy metals were quantified using the ICP-MS method. Oxidative stress indicators, such as catalase, superoxide dismutase, and malondialdehyde, were also evaluated. The study found E. coli in 26.05% of samples, with 50% exhibiting resistance to doxycycline and sulfamethoxazole + trimethoprim. Heavy metal concentrations, except for lead, were significantly higher in E. coli-positive samples (P < 0.001). Catalase activity was present in E. coli-negative samples, but malondialdehyde levels were higher in positive samples. A negative correlation was observed between arsenic levels and catalase activity, while a positive correlation existed between arsenic and malondialdehyde. Additionally, iron showed a positive correlation with catalase and superoxide dismutase. Toxic metals like cadmium and mercury exceeded permissible limits in E. coli-positive samples compared to negative ones. The results underscore the importance of routine microbial and chemical monitoring of milk to ensure public health. Strict control measures must be implemented to produce safe, high-quality milk.