Hospital Wastewater as a Reservoir of Contaminants of emerging concern: A Study Report From South America, Chile

Hospital wastewater is a complex effluent containing a wide range of biological and chemical contaminants, including pharmaceuticals, pathogens, and antimicrobial re-sistance determinants. These discharges pose a growing threat to aquatic ecosystems and public health, particularly in regions where wastewater treatment is insufficient. This study aimed to characterize the chemical and microbiological composition of untreated effluent from a tertiary care hospital in southern Chile, focusing on contaminants of emerging concern. Methods: Wastewater samples were collected at the hospital outlet be-fore any treatment. The presence of two commonly used pharmaceutical compounds, pa-racetamol and amoxicillin, was quantified using high-performance liquid chromatog-raphy (HPLC). Bacterial isolation was performed using selective media, and antibiotic susceptibility testing was conducted via the disk diffusion method following CLSI guide-lines. In addition, metagenomic DNA was extracted and sequenced to assess microbial community composition and functional gene content, focusing on the identification of re-sistance genes and potential pathogens. Results: Paracetamol were detected in all sam-ples, with concentrations around 200 µg/L. No amoxicillin was detected. A diverse set of bacteria was isolated, including genera with known pathogenic potential. Antibiotic sus-ceptibility testing revealed a high prevalence of multidrug-resistant strains. Metagenomic analysis showed the dominance of Proteobacteria and Bacteroidota, along with genes re-lated to antibiotic resistance, efflux pumps, and virulence factors. Functional gene analy-sis suggested that several key resistance mechanisms are being released into the environ-ment through untreated effluent. Conclusions: Our findings confirm that hospital wastewater serves as a significant reservoir of pharmaceutical residues, pathogenic mi-croorganisms, and resistance genes, emphasizing the urgent need for targeted treatment strategies to mitigate environmental and health risks.