The Nexus of Heavy Metals and Antibiotic Resistance: Investigating Industrial Effluent-Associated Bacterial Strains

Industrial effluents are reservoirs for multidrug-resistant (MDR) bacteria due to co-selection pressure from heavy metals and residual antibiotics. This study assessed the prevalence of heavy metal- and antibiotic-resistant bacteria in wastewater from four industrial sectors in the Hayatabad Industrial Zone, Peshawar, Pakistan. Twenty-three bacterial isolates were obtained, including Pseudomonas aeruginosa , Bacillus cereus , Staphylococcus aureus , and Escherichia coli . These strains showed notable resistance to chromium (100 µg/mL), cadmium (64 µg/mL), and zinc (64 µg/mL). Antibiotic susceptibility testing revealed a strong link between metal tolerance and MDR phenotypes. P. aeruginosa and E. coli showed high resistance to colistin (39.13% and 34.7%, respectively), while S. aureus exhibited vancomycin resistance (43.47%). Statistical analysis confirmed significant correlations between metal resistance and antibiotic resistance, particularly for gentamicin (r = 0.81, p = 0.003), colistin (r = 0.79, p = 0.004), and vancomycin (r = 0.77, p = 0.005). 16S rRNA sequencing confirmed isolate identities, showing > 99% homology to reference strains. The results highlight industrial wastewater as a critical source of resistance gene dissemination. These findings emphasize the urgent need for improved wastewater treatment, regulatory controls, and continuous environmental monitoring to combat the spread of MDR pathogens and address rising antimicrobial resistance threats.