Survival of health significant bacteria in packaged drinking water: planktonic versus sessile life

In the present study an attempt has been made to evaluate the quality of packaged drinking water (108 samples) and experimental studies were carried out to determine the growth kinetics of health significant bacteria in various drinking water microcosms and biofilms developed on the walls of glass and PET containers. While HPC were analysed using R2A medium, membrane filter technique with appropriate media were used for the enumeration of Total Coliforms (TC), Faecal Coliforms (FC), and Faecal Streptococci (FS). Nutrient concentration in these samples was monitored using standard methods. Various types of drinking water microcosms prepared in triplicate for monitoring the biofilm analysis. The viable bacterial load was determined by plate count method using R2A medium and biofilm development was observed using Scanning Electron Microscope. Survival of selected microorganisms such as Escherichia coli, Pseudomonas fluorescence and Aeromonas hydrophila in bottled drinking water and biofilms were studied using microcosms. Risk associated with HPC bacteria were carried out in terms of antibiotic resistance analysis and virulence factors. The nutrient concentration of these water samples was very low and found to be within the permissible limits of WHO. Biofilm associated life was encountered in most samples and found to be higher in number than their planktonic counterparts. TC was encountered in most of the samples, FC and FS in 10% and 34% samples respectively. Significant positive correlations were found between TC and FC, HPC of water and TC and HPC of water and FC. The growth patterns of the biofilm associated bacteria indicated periodical build up and sloughing off biofilms. Many of the HPC bacteria from the drinking water were multi drug resistant and showed Beta haemolytic property. Survival kinetics of the selected bacteria showed that they were able to live better in biofilms, though the capabilities varied significantly among them. Biofilm development was more on glass surface. The result of the study calls for stringent monitoring of packaged drinking water quality by regulatory authorities and refrigeration of drinking water at all times by retail and wholesale vendors.