Evaluation of bottled drinking water and occurrence of multidrug-resistance and biofilm producing bacteria in Nepal

Health consequences arising from unsafe drinking water and water insecurity lead to increased reliance on usage of bottled water. Biofilm-producing antibiotic-resistant bacteria in bottled water may pose a risk to public health. This study aims to assess the quality of bottled drinking water with a focus on biofilm-producing and drug-resistant coliform. We analyzed 60 bottled water samples of 30 different brands purchased from Kathmandu for physicochemical and microbial analysis. The parameters pH, iron, total coliform count, Escherichia coli count, and fecal coliform count exceeded National Drinking Water Quality Standards, 2022 in 30.00%, 16.67%, 66.67%, 23.33%, and 16.67% of samples, respectively. Water quality index measurement showed 36.67% and 6.67% of bottled water samples were categorized as grade A and grade B indicating excellent and good water quality, respectively. However, 56.67% of bottled water samples fall under grade E meaning unsuitable for drinking. Among 14 coliform isolates, 85.71% and 14.29% were identified as E. coli and Klebsiella spp, respectively. The antibiotic susceptibility testing revealed that 28.57% of the isolates were multidrug-resistant and Gentamicin resistant isolates comprised 71.43%. However, none of the isolates were carbapenem (meropenem) resistant. In this study, 42.87% of the isolates were found biofilm producers with 14.29% each of strong, moderate, and weak biofilm producers. The genetic potential of biofilm-producing capacity of the isolates was assessed by Polymerase Chain Reaction amplification of bcsA and csgD genes. Our results showed that 66.67% and 50.00% of the isolates harbored bcsA and csgD genes, respectively. This study highlights potential public health hazards associated with the consumption of bottled water containing biofilm-producing and drug-resistant bacteria in Nepal.