Bacteriological assessment of drinking water sources in an institutional campus in Northeast India using the most probable number method

Background: Safe drinking water is essential for preventing water-borne diseases and maintaining public health. Microbial contamination of drinking water remains a concern, and coliform bacteria are widely used as indicator organisms of microbiological safety. Methods: A laboratory-based cross-sectional study was conducted in May 2023 at the Regional Institute of Paramedical and Nursing Sciences (RIPANS), Aizawl, Mizoram. Forty-two drinking water samples were collected aseptically from hostels, academic blocks, administrative offices, library and canteen areas. Samples were analyzed using the Most Probable Number (MPN) technique for coliform detection. Positive samples were further examined by culture on Eosin Methylene Blue (EMB) agar and Gram staining. Results: Of 42 water samples, 8 (19.0%) were positive for coliform organisms and 34 (81.0%) showed no bacteriological contamination. Positive samples showed gas production in lactose broth, green metallic sheen colonies on EMB agar and Gram-negative rod-shaped bacteria consistent with Escherichia coli. Contamination was detected in hostels, academic blocks, canteen, library and administrative areas. Conclusions: Detection of coliform organisms indicates possible fecal contamination in parts of the institutional water supply system. Regular microbiological surveillance, maintenance of water purification systems and periodic sanitation of storage facilities are needed to support safe drinking water in institutional settings.