Multidrug-resistant Pathogenic Bacteria in Lake Sediments: Evidence from Poondi Lake, Tamil Nadu, India

The present study evaluated the presence of antibiotic resistance bacteria in sediment samples from the Poondi reservoir, Tamil Nadu, India. Sediment samples were collected from four different sites in triplicate. Bacterial loads varied across the sites, with higher total viable counts observed at locations receiving continuous sewage inflow, indicating nutrient enrichment–driven microbial proliferation. From each agar plate, one dominant and distinct bacterial colony representing each site was chosen and subjected to a series of biochemical analyses for identification. The results revealed the presence of Shigella spp., Salmonella spp., Proteus spp., and Acinetobacter spp. Further, these opportunistic pathogens were tested for antibiotic susceptibility using the disc diffusion method. All the four bacterial isolates were found to be multi-drug resistant against the 10 tested antibiotics, with enhanced resistance to broad spectrum antibiotics including carbapenems and quinolones. The findings provide baseline evidence on sediment-associated antibiotic resistance in a major drinking water reservoir and highlight the environmental persistence of clinically relevant resistant bacteria. This study contributes valuable data for understanding the role of freshwater sediments as reservoirs and potential sources of antibiotic-resistant pathogens in aquatic ecosystems. Implementing effective wastewater treatment, controlling sewage inflow, and strengthening routine monitoring of antibiotic resistance in sediments are essential to mitigate the spread of resistant bacteria in freshwater reservoirs.