Abstract Background: Mastitis is an inflammation of the mammary gland thatusually caused by bacterial infection of udder tissues. Clinical mastitis still causes major losses in production and increases treatment costs and premature animal culling. E. coliis one of the most important environmental bacteria which plays an important role in the development of clinical mastitis. The purpose of this study was to evaluation the contamination of clinical mastitis due to E. coli to help treatment and prevention. Materials and Methods: A total of 130milk samples were collected fromdairy farms in Hamedan province of Iran. The sampleswere transferred to the laboratory and werethen cultured onMacConkey and blood agar media. In the following, the isolates were confirmed to be Escherichia coliusing common biochemical tests. Results: The results showed that 61 (79.3%) out of 130 randomly collected milk samples were contaminated with Escherichia coli. Discussion and Conclusion: Based on our results, a high prevalence of contamination with E. coli was observed in the examined milk samples. Hence, it is suggested to take appropriate measures to control this infection.
