This evolution-based study aimed to reliably identify the epidemiological prevalence of Escherichia coli that was recovered from affected milk of cattle by mastitis, study the evolution of this bacterium, and describe some isolates using polymerase chain reaction (PCR) technique and DNA sequencing. Here, we collected 50 cattle milk samples and submitted them to conventional bacterial isolation and identification using enrichment culture method and biochemical tests. Then, we confirmed the results by PCR technique based on 16S ribosomal RNA gene. The results showed that E. coli was isolated from cattle at (36%), and this was confirmed by PCR that showed highly specific detection of E. coli isolates at (100%). DNA sequencing of partial 16S ribosomal RNA gene showed (99%) homological identity with NCBI-Blast E. coli isolates and the phylogenetic analysis showed genetic similarity (0.5 genetic changes). In conclusion, this was the first study in Iraq to report genetic relationship between E. coli isolated from milk of mastitis-infected cattle. Therefore, it is essential to define the role of animals as an important source in the distribution of some pathogens that are related to public health.

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