Adaptive Resilience: Unraveling the Path of Heavy Metal Tolerance in Multidrug Resistant Pathogens

Abstract

Co-existence of heavy metal tolerance and antibiotic resistance in bacterial strains pose potential threats to human health and environment. In recent decades, heavy metal pollution has caused selective pressure that leads to the development of multiple drug resistance among bacterial populations. Escherichia coli, Pseudomonas aeruginosa and Staphylococcus cohnii were used in the study. Out of 8 antibiotics tested, it was observed that E.coli was resistant to four, S.cohnii and P. aeruginosa were resistant only to three antibiotics. The isolates were found to grow at high concentration of copper (CuSO4) and varying degrees of chromium (K2Cr2O7) with all the three being sensitive to mercuric chloride (HgCl2). E. coli, S. cohnii and P. aeruginosa were inhibited at 0.84±0.05, 6.79±0.07 and 2.54±0.02 μM ml-1 respectively by chromium salt; similarly, E. coli, S. cohnii and P. aeruginosa had a MIC of 1.56±0.03 μM ml-1, 1.25±0.05 μM ml-1 and 1.56±0.05μM ml-1 and for copper, E. coli, S. cohnii and P. aeruginosa had a MIC of 8.20±0.05, 9.20±0.01, 7.18±0.05μM ml-1 respectively. Further studies were carried out by agarose gel electrophoresis and SDS-PAGE for the characterization of R-plasmid and heavy metal stress protein among the isolated bacteria. The qPCR was used for identification of antimicrobial resistant genes. A phylogenetic study was performed on S. cohnii to understand its evolutionary traits. The results provide insight into the co-occurrence of antibiotic resistance and heavy metal tolerance in clinically important bacterial communities, which may create severe health issues in the coming decades.