Antimicrobial resistance is not confined to patients or hospital wards; it is also present in hospital wastewater, which contains traces of antibiotics, resistant bacteria and DNA fragments that enable bacteria to acquire resistance.

Without adequate treatment, this wastewater can enter rivers and coastal waters, where resistant organisms may mix with environmental bacteria and persist in the ecosystem, contaminating water consumed by humans as well as fruits and vegetables irrigated with it.

This challenge was examined in a recent study published in the Scientific Reports led by Dr. Mahmoud Wazne, professor at the LAU School of Engineering, and coauthored by postdoctoral research fellows at LAU, Drs. Stephanie Greige and Josephine Al Alam, as well as Dr. Moustapha Harb and Lama Ramadan (MS ‘22) from the New Mexico Institute of Mining and Technology in the US.

The paper examines the spread of genes conferring resistance to many clinically critical antibiotic classes through hospital wastewater discharges in Lebanon.

The team collected samples of untreated wastewater from 13 hospitals across the country and tested each for different water quality measures. This was followed by two tests: One to identify the main bacterial groups present and another to measure genes that contribute to antimicrobial resistance (targeted resistance genes) and its spreading (targeted mobility genes). 

Across the 13 hospitals, the researchers detected 86 to 89 of the targeted genetic markers in each sample, meaning that most of the genes they searched for were present almost everywhere, though the mix of microbes differed sharply from one hospital to another.  

The study also identified the most prominent resistance traits and what might influence them. Genes linked to resistance to several widely used antibiotic families were among the most abundant, including penicillin-like drugs. The wastewater also carried many gene-sharing tools, pieces of DNA that help bacteria swap resistance. Several nutrient measures, especially nitrogen and phosphorus, showed statistically significant positive correlations with multiple resistance gene classes. 

According to Dr. Wazne, this finding “indicates nutrient-rich hospital wastewater, which could create favorable conditions for microbial proliferation and the persistence of bacterial populations carrying antibiotic resistance genes.”

Differences between broad regions were not statistically significant, but when hospitals were grouped by similar microbial and resistance profiles, regional effects appeared within those clusters. “This effect is likely influenced by factors such as the presence of refugee populations and similar antibiotic usage practices,” said Dr. Wazne. 

The study offers Lebanon a clearer, data-driven basis for action. Hospital wastewater can act as an early warning system for what is circulating in clinical settings and a potential launch point into the wider environment. Routine monitoring, stronger treatment of hospital effluents and policies that reduce unnecessary antibiotic use can work together to slow the spread of antimicrobial resistance before it becomes even harder to contain. 

When asked about the next step, Dr. Wazne mentioned that “implementing targeted surveillance and considering on-site pre-treatment strategies could help reduce downstream dissemination into municipal sewer networks and receiving waters.” 

He added that the results were shared with the Ministry of Energy and Water, which expressed interest in expanding the scope of the study to include other emerging contaminants, forming a basis for future collaboration. 

To browse more scholarly output by the LAU community, visit our open-access digital archive, the Lebanese American University Repository (LAUR).