Wastewater surveillance unveils the impact of mass gatherings on antimicrobial resistance after the COVID-19 pandemic in Saudi Arabia

Mass gatherings (MGs), such as Hajj and Umrah, gather vast and diverse populations and potentially contribute to antimicrobial resistance (AMR) in the host country. However, assessing this impact is challenging due to the lack of a suitable baseline. During the COVID-19 pandemic restrictions and lifting, 185 sewage samples were collected from four wastewater treatment plants affected by MG and a control wastewater treatment plant, covering 3 Hajj seasons and 2 Ramadan periods. Here we show that despite no overall increase in total antibiotic resistance gene level, metagenomic analysis revealed that MGs introduced antibiotic resistance genes, including blaPER, into the local sewage. This gene was also found in a genomic island facilitated by the IS26 array, which was identified in viable opportunistic pathogens, including Shewanella putrefaciens, Shewanella xiamenesis and Aeromonas media, indicating emerging AMR threats to the local environment. These insights are crucial for informing public health strategies and interventions, ensuring better preparedness and response to AMR dissemination during MGs. Mass gatherings can impact the antimicrobial resistance in the environment. Surveillance of wastewater in areas of Saudi Arabia affected by mass gatherings after the lifting of COVID-19 pandemic restrictions shows the introduction of new antibiotic resistance genes into local sewage.