Correlation between plasmid presence & antibiotic resistance: in enteric bacteria; isolated from different water bodies inside Dhaka City

Abstract

Antimicrobial resistance (AMR) is an endemic issue of public health in the world, and there is increasing evidence that surface water bodies are significant environmental reservoirs of antibiotic-resistant bacteria. This study has analyzed the relationship between the occurrence of plasmids and antibiotic resistance in the pathogenic enteric bacteria that develop in surface water sources in Dhaka Metropolitan City. To identify the contribution of anthropogenic interference to the waters of three urban water bodies, namely, Hatirjheel, Curzon Hall, and Ramna Lake, water samples were taken from January to June 2025, and with varying degrees of anthropogenic impact. Three clinically and ecologically important bacteria, i. e. Escherichia coli, Salmonella spp., and Vibrio cholerae, were the subject of the investigation. The selective and differential media (EMB, TCBS, and SS agar) were used to perform isolation, and antibiotic susceptibility testing was conducted to identify the profiles of resistance. Molecular validation was done by polymerase chain reaction (PCR) and plasmid isolation done to assess genetic basis of resistance. PCR amplicons and plasmid DNA were analyzed utilizing agarose gel electrophoresis, which allowed performing the correlation analysis between the plasmid carriage and the observed resistance patterns. The results showed that the prevalence of PCR-confirmed antibiotic-resisting isolates and plasmid-bearing isolates were very high in Hatirjheel and then in Ramna Lake, but relatively low in Curzon Hall. There was a close correlation existing between the presence of plasmids and the presence of multidrug resistance thereby highlighting the importance of plasmid-mediated horizontal gene transfer in water.