Vol. 7, Issue 1, Part B (2025)

Water contamination, particularly in drinking water, remains a critical public health concern worldwide. This study aimed to investigate the presence of Escherichia coli (E. coli) bacteria in reverse osmosis (RO) water systems across Karbala Governorate and its surrounding areas. A total of 100 water samples was collected from RO water filling stations in four regions Karbala Center Tuwairij District Al-Hussainiya District and Ain Al-Tamr District. Samples was cultured on selective and differential media including MacConkey agar and eosin methylene blue (EMB) agar to identify E. coli isolates Biochemical tests such as catalase oxidase indole, methyl red and sugar fermentation assays were conducted to confirm bacterial identification. The result revealed that three isolates of E. coli were identified, representing an isolation rate of 4%.The highest contamination rates were observed in Al-Hussainiya District(2.5%) and Ain Al-Tamr District (1.7%)while no contamination was detected in Karbala Center and Tuwairij District This study highlights the potential inefficiencies in water treatment processes and emphasizes the importance of regular monitoring and improved hygiene practices at water filling stations to ensure safe drinking water for the population.