Seasonal emergence of pathogenic bacteria in drinking water
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
The impact of seasonal variations on microbial diversity of drinking water poses an imminent
threat to public health. As such the seasonal dynamics of drinking water quality
characteristics were investigated during the year 2019-2020 in Punjab. A total of N=600
drinking water samples from various sources and utilities were analysed for bacteriological
and physicochemical attributes; viz heterotrophic plate counts (HPC), total coliforms (TC),
faecal coliform E. coli, emerging pathogens, pH, conductivity (EC), and TDS. A total of
66.3% (n=398) samples were tested positive for the presence of coliforms. The mean HPC
and TCC were found to differ significantly during seasons (summer, monsoon, and winter) of
the year (P < 0.05). There were considerable seasonal variations in prevalence of indicator E.
coli (16.7-60%) as well as the emerging pathogens in contaminated drinking water samples.
Statistical analysis of the dataset showed significant positive correlation trends between
temperature and TCC (r = 0.785), E. coli (r = 0.690) and HPC (r = 0.678). The prevalence of
emerging pathogens in contaminated samples and temperature showed a significant positive
correlation for Enterococcus spp., Campylobacter spp., Vibrio spp. and inverse significant
correlation for Aeromonas spp., Yersinia spp., Pseudomonas spp. and Listeria spp. The
bacterial pathogens Klebsiella spp., Shigella spp., Staphylococcus spp., Salmonella spp. were
detected from contaminated samples throughout the year in low percentages regardless of
temperature influences. The concurrence of faecal indicator E. coli and emerging bacterial
pathogens in contaminated samples was weak and variable. The bacterial isolates from
drinking water tested for antibiotic sensitivity assay showed MAR index range of 0.12-0.87.
The commercially available UV filter was explored as a remedial technology for
bacteriologically contaminated water. Its effectiveness under applicable conditions debunks
the common belief about the advanced disinfection potential. The presence of injured
coliforms and bacterial pathogens showing marked phenotypic and antibiotic sensitivity
changes post-treatment raises the alarming concern of consumer safety. Lastly collection of a
large dataset at high frequency over a period of one calendar year has enabled the
characterization of previously undocumented seasonal dynamics in the drinking water
characteristics and highlights the need for reframed standard methods to enhance pathogenspecific
assessment for better risk management.
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Citation
Pandey, Swati (2020). Seasonal emergence of pathogenic bacteria in drinking water (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.