Comparative analysis of plasmid presence and antibiotic resistance profiles in water samples with a focus on Dhaka City's water bodies (Dhanmondi & Gulshan Lake)

Abstract

Antimicrobial resistance (AMR) is a growing global public health concern, with environmental reservoirs contributing significantly to the spread of antibiotic-resistant bacteria. Urban surface water bodies in densely populated cities are recognized as important hotspots due to continuous exposure to domestic, medical, and industrial waste. In Dhaka, Bangladesh, rapid urbanization and inadequate wastewater management have intensified this problem. This study comparatively analyzed the antibiotic resistance profiles and plasmid presence of Escherichia coli, Salmonella spp., and Vibrio cholerae isolated from water samples collected from Dhanmondi Lake and Gulshan Lake. Samples were processed using selective culture methods, followed by molecular confirmation through polymerase chain reaction (PCR). Antibiotic susceptibility testing was conducted using the Kirby–Bauer disk diffusion method, and plasmid DNA isolation was performed to assess the potential role of plasmids in resistance dissemination. Results indicated a high prevalence of antibiotic-resistant isolates in both lakes, with several strains exhibiting multidrug resistance. Differences in resistance patterns between the two sites suggest variation in environmental contamination pressures. A substantial proportion of isolates carried plasmids, highlighting the potential contribution of horizontal gene transfer to environmental AMR spread. These findings underscore the role of urban water bodies as reservoirs of antibiotic-resistant bacteria and resistance-associated plasmids, emphasizing the need for continuous monitoring and improved waste management strategies in rapidly urbanizing regions.