Assessment of Heavy Metal Accumulation and Antibiotic Resistance in Biofilm-Forming Bacteria Isolated from Fish Pond Water

A Food Safety Concern

Abstract

Heavy metals, the most potent contaminants of the pond water environment, are transmitted into the food chain through accumulation in aquatic life. Several bacteria harbor these heavy metals, resulting in antibiotic resistance and enhanced biofilm formation. This research aimed at assessing heavy metal accumulation and antibiotic resistance in biofilm-forming bacteria isolated from pond water. Pond water samples were collected, and isolation and identification were carried out using the pour plate method and Bergey’s Manual of Systematic Bacteriology, respectively. Biofilm formation, antibiotic susceptibility, and detection of heavy metals were done on the highly and moderately biofilm-producing bacteria. Molecular identification and detection of resistance genes were done on the isolates with high concentrations of heavy metals. A total of 41 bacteria were isolated, with a high concentration of coliform and heterotrophic bacteria. Bacteria isolated include Citrobacter diversus (41%), Escherichia coli (27%), Klebsiella sp. (15%), Enterobacter (10%), Clostridium sp. (5%), and Enterococcus sp. (2%). Twenty-six bacteria were high biofilm formers, while three (3PWS1, 3PWS3, 3PWS5, and 3PWM5) had the highest MAR index. The heavy metal accumulation includes iron (15.160–23.186 ppm), lead (0.194–1.113 ppm), cadmium (0.0–0.500 ppm), nickel (0.127–0.0331 ppm), and cobalt (0.440–2.946 ppm). The highest concentration was observed in isolates 3PWS3 and 3PWM3, and they were molecularly identified as Escherichia coli ROF 13 and Enterococcus fecalis ROF 11 with the accession numbers PV715894 and PV715893, respectively. The antibiotic resistance genes revealed the presence of TEM in both Escherichia coli and Enterococcus sp. and the absence of CTX genes. Strong regulations and enforcement are needed to control pollution, and educating communities and fish farmers is key to sustainable practices.