Heavy Metal and Antibiotic Resistance in Bacteria from a Wastewater Treatment Plant

Bacterial resistance to heavy metals and antibiotics is a global concern to public health, animals, and ecosystems. This study was conducted to determine bacteria with multiple heavy metals and antibiotic resistance from the effluent of a wastewater treatment plant. Heavy metal concentrations in the effluents were analyzed using Atomic Absorption Spectrophotometer (AAS). Selective isolation of heavy metal-resistant bacteria, metal tolerance concentration, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) was done using heavy metals salts at different concentrations (25-750 ppm) incorporated in broth and Mueller Hinton agar (MHA). The isolates were identified based on their phenotypic and 16 rRNA analysis. The antibiotic resistance was determined by the disk diffusion method. The plasmid DNA of the bacterial isolates was analyzed on agarose gel electrophoresis. Four bacteria exhibited resistance to heavy metal concentrations between 200 -750 ppm. The isolates were identified as Alcaligenes, Paenalcaligenes, Providencia and Klebsiella species. The bacteria were resistant to 2 or more antibiotics with Multiple Antibiotic Resistance (MAR) index between 0.25 - 0.75. All the isolates possessed plasmids, and the resistance in the bacteria was either chromosome or plasmid-borne. The bacterial isolates obtained could serve as potential candidates for the bioremediation of heavy metal contaminated effluents. However, the multiple antibiotic resistance could result in bacteria proliferation, contributing to the maintenance and spread of antibiotic-resistant disease-causing bacteria.