Microbiological quality assessment of bottled drinking water in Uganda

Abstract

Access to microbiologically safe drinking water remains a critical component of public health, especially in rapidly urbanizing regions such as Kampala, Uganda. Bottled water has increasingly become a preferred source of drinking water for many urban dwellers due to concerns about the safety of piped or untreated water. However, the microbiological quality of bottled water remains under-investigated in Uganda. This study aimed to assess the microbiological quality of bottled drinking water sold in shops and supermarkets in Kampala using Total Plate Count (TPC) and mSuperCARBA™ methods. A cross-sectional experimental design was employed. A total of thirteen (13) different bottled water brands were collected from various retail outlets including supermarkets, kiosks, and street vendors across Kampala District. Due to laboratory resource limitations, only seven (7) of these samples were subjected to full microbiological analysis. Nutrient Agar was used for estimating the total bacterial load through standard plate count methods, while mSuperCARBA™ was used for the detection of pathogenic bacteria such as Escherichia coli and other coliforms. Water samples were serially diluted (10⁻¹ and 10⁻²), and 0.1 mL from each dilution was plated in duplicate. The plates were incubated at 37°C for 24–48 hours for TPC, and 35–37°C for 18–24 hours for pathogen detection on mSuperCARBA™ . Colony counts were recorded and used to calculate CFU/mL for each brand. Results revealed that Hema, Rwenzori, Ice Water, and Pot Water had no detectable heterotrophic bacteria,hence microbiologically safe and complied with WHO (2017) and Uganda National Bureau of Standards (UNBS, 2020) . Krystal and Westlake recorded CFU values of exactly 100 CFU/mL technically compliant at borderline microbiological safety suggesting small post-production contamination. Hill Water, was non-compliant, registering a TPC of 300 CFU/mL implying possible flaws in post-treatment handling, bottling, or storage. Notably, no visible growth was observed on mSuperCARBA™ plates across all tested samples, suggesting the absence of E. coli and coliform contamination. Regulatory agencies such as UNBS and health authorities should strengthen post-market surveillance to ensure continued consumer safety.