Risk assessment and biofilm formation of bacterial communities associated with drinking water distribution system

Abstract

Aim : Potable water can be contaminated with variety of bacterial pathogens during the distribution process. The aim of this study was to analyze the bacterial risks associated with drinking water supply system of the city Kasur, Pakistan. Methodology: Water analysis was accomplished by following the most probable number (MPN) method. Bacterial diversity was determined by 16S rRNA gene sequencing. Screening for O157 antigen was conducted for all the identified strains of Escherichia coli. Strains were also screened for antibiotic susceptibility and biofilm formation. Results: Analysis showed > 2400 MPN index for few water samples. 16S rRNAsequencing confirmed the presence of bacterial strains belonging to the genera of Escherichia, Pseudomonas, Bacillus, Exiguobacterium, Klebsiella, Acinetobacter, Aeromonas, Enterobacter, Citrobacter and Shigella. Serological analysis also detected the presence of pathogenic strains of E. coli O157. Antibiotic sensitivity pattern showed the resistance of strains against nitrofurantoin, cephalexin, nalidixic acid and ampicillin. For biofilm formation, Ex. artemiae DG1 and An. haemolyticus J4 were the most active biofilm producer in single cultures. Interpretation : Majority of the water samples were contaminated in terms of coliforms. Biofilm formation by bacterial strains indicated that water distribution network might be colonized by potential human pathogens.