<![CDATA[The microbiological quality of refill drinking water is an important aspect in ensuring the safety of water consumed by the community. The presence of Escherichia coli can be used as an indicator of fecal contamination and is one of the important parameters in assessing the microbiological quality of drinking water. This study aims to compare the microbiological quality of reverse osmosis (RO) and mineral refill drinking water based on the presumptive detection of Escherichia coli. This study uses a descriptive observational design with a comparative approach based on laboratory examination. A total of 40 refillable drinking water samples, consisting of 20 RO samples and 20 mineral samples, were examined at the Microbiology Laboratory of STIKES Papua from May to July 2026. The examination was conducted through presumptive testing using Lactose Broth (LB), confirmatory testing using Brilliant Green Bile Broth (BGLB), and observation of colony characteristics on Eosin Methylene Blue (EMB) agar. The research results show that 8 out of 40 samples (20%) indicated presumptive positive results for Escherichia coli. In the RO group, 1 positive sample (5%) was found, while in the mineral group, 7 positive samples (35%) were found. The Fisher’s exact test results showed a p-value of 0.044 (p<0.05), indicating a difference in the proportion of presumptive Escherichia coli results between RO and mineral refill water. Descriptively, the proportion of positive results was higher in the mineral water group compared to the RO group. These findings highlight the importance of microbiological quality control and the implementation of good hygiene and sanitation practices at all stages of management and refilling of drinking water. Because the examination stopped at the EMB medium, the positive results in this study are presumptive and not yet a definitive confirmation of Escherichia coli. Further examination using biochemical tests is necessary to confirm the identity of the bacteria]]>
