Microbial safety and quality assessment of drinking water from various water sources in Punjab, India

Waterborne illnesses caused by contaminated water are increasing due to lack of accessibility to clean drinking water. This study investigates the microbial safety and antibiotic resistance profiles of waterborne microbes in different drinking water sources of Ludhiana, Punjab. Using most probable number as the selection criteria, 66% samples showed the presence of coliforms and other microbes with count ranging from 3 to 2600/100 mL. Overall, 50% of tap water samples were found to be unacceptable, followed by submersible (25%) and filters/RO systems (20%). The results revealed the presence of microbial contaminants, including <i>Pseudomonas</i> spp. <i>Staphylococcus</i> spp. <i>E. coli, Klebsiella</i> spp. <i>Salmonella</i> spp. <i>Enterococcus</i> spp. <i>Citrobacter</i> spp. and <i>Proteus</i> spp. Furthermore, antibiotic susceptibility testing by well diffusion method showed high levels of resistance, particularly to β-lactams, trimethoprim/sulfamethoxazole, monobactam and cephalosporins, highlighting the critical issue of antibiotic-resistant bacteria (ARB) in water systems. Maximum multiple drug resistance index was seen in <i>Enterococcus</i> spp. (0.916), followed by <i>Proteus</i> spp. (0.83), <i>Pseudomonas</i> spp. and <i>Staphylococcus</i> spp. (0.58). The study underscores the importance of stringent necessity for water quality monitoring to mitigate the risks posed by ARB. Further, advanced molecular detection of antibiotic resistance genes is required to enable targeted interventions and prevent their spread.