Comparative study on antibiotic resistance profiles and plasmid presence in water samples focusing inside Dhaka

Abstract

The microbial contamination threat to Bangladesh's surface water sources is being exacerbated by the rapid urbanisation, discharge of industries, and insufficient waste water treatment facilities. Hatirjheel Lake, one of the largest urban water bodies in Dhaka city, is continuously exposed to pollution from domestic sewage, runoff, and man-made waste. Consequently, it is at risk of harbouring a variety of pathogens. The objective of the current investigation was to isolate, identify, and compare the bacterial strains isolated from Hatirjheel Lake water with respect to their antibiotic resistance pattern and plasmid-mediated resistance. Water samples were collected from various locations in Hatirjheel Lake over a nine-month period and subjected to conventional microbiological procedures. Escherichia coli, Salmonella spp., and Vibrio cholerae were isolated and identified using selective and differential culture media, specifically Eosin Methylene Blue (EMB), Salmonella-Shigella (SS), and Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) agars, respectively, based on colony appearance. Escherichia coli was the most prevalent bacterial isolate (n=146), followed by Vibrio cholerae (n=144) and Salmonella spp. (n=115). A total of 405 bacterial isolates were identified. The confirmation of E. coli and V. cholerae was conducted at the molecular level using species-specific genes through PCR. The culture-based method was employed to identify Salmonella spp. The bacteria were isolated on SS agar medium, and colonies with a black center were observed, indicating the production of hydrogen sulphide. Furthermore, the Kirby-Bauer disc diffusion test was employed to conduct an antibiotic susceptibility test (AST) of the pathogens using ten antibiotics that are frequently employed. Additionally, plasmid isolation was employed to ascertain the correlation between MDR status and the presence of plasmids. The water bodies of Hatirjheel Lake are contaminated with hazardous pathogenic organisms, which pose a significant threat to public health. This conclusion can be drawn from the findings of this investigation. The health risks associated with the discovery of MDR organisms in such water bodies are also alarming.