Abstract:

Hospital wastewater has emerged as an important environmental reservoir for heavy metals, multidrug-resistant bacteria, and antibiotic resistance genes (ARGs), posing significant ecological and public health concerns. This study assessed the occurrence of antibiotic resistance genes and heavy metal co-contamination in hospital wastewater discharges from selected healthcare facilities in Southern Nigeria. A cross-sectional analytical design was adopted, and 20 composite wastewater samples were collected for physicochemical, microbiological, heavy metal, and molecular analyses. Physicochemical parameters were determined using standard methods, while heavy metals (Fe, Zn, Cu, Pb, Cd, Cr, and Ni) were quantified using Atomic Absorption Spectrophotometry. Bacterial isolates were identified using conventional microbiological techniques, and antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method. Polymerase Chain Reaction (PCR) was employed to detect the presence of the blaTEM, blaCTX-M, blaNDM, mecA, sul1, tetA, qnrS, and intI1 genes. The Heavy Metal Pollution Index (HPI), Pearson correlation analysis, and Principal Component Analysis (PCA) were used to interpret the data. The results showed elevated Biological Oxygen Demand and Chemical Oxygen Demand, indicating high organic pollution. Lead, cadmium, chromium, and nickel exceeded recommended discharge limits in several samples, while 40% of the wastewater samples were classified as highly polluted based on HPI. Molecular analysis revealed a high prevalence of intI1 (90.0%), blaTEM (85.0%), sul1 (80.0%), and blaCTX-M (75.0%). Significant positive correlations were observed between heavy metals and ARGs, suggesting possible co-selection mechanisms. Principal Component Analysis explained 82.1% of the total variance, indicating that heavy metals, organic pollution, and hospital activities were the principal factors influencing wastewater quality. The study demonstrates that untreated hospital wastewater constitutes an important environmental source of heavy metals and antibiotic resistance genes, underscoring the urgent need for effective wastewater treatment, continuous environmental surveillance, and strengthened antimicrobial resistance control policies in Nigeria.