Five years of wastewater surveillance reveal COVID-19-Associated amplification and seasonal shifts in bla and bla .

Publication date: Dec 01, 2026

Antimicrobial resistance (AMR) has intensified in recent years, raising concerns about the potential impact of the COVID-19 pandemic on AMR dynamics. However, the influence of pandemic on the enviromental occurrence and dissemination of antibiotic-resistant genes (ARGs) remains under investigation. Wastewater-based epidemiology (WBE) provides an integrated view of community-level AMR dynamics, yet long-term assessments spanning the pandemic period remain limited. This study investigated the occurrence, temporal patterns, and seasonal behavior of two clinically relevant carbapenemase genes, bla and bla , in raw wastewater from the Attica region over a five-year period (July 2021-September 2025). A sensitive and specific 3-plex qPCR assay was developed and analytically validated for the simultaneous quantification of bla , bla , and 16S rRNA, the latter serving as a stable bacterial load indicator. Across the monitoring period, bla was consistently detected, showing a steady increase and reaching its highest concentrations in 2023, while bla exhibited intermittent but pronounced surges, particularly in 2023. Comparison with community SARS-CoV-2 viral loads suggest temporal association with AMR signatures in wastewater. Seasonal analysis showed non-uniform patterns, with atypical warm-season peaks of both ARGs in 2023-2024 and a return to classical autumn-winter peaks in 2025, suggesting a gradual restoration of pre-pandemic seasonality. To our knowledge, this is among the first long-term WBE studies to characterize post-COVID-19 shifts in ARG occurrence and seasonality. The results demonstrate that the pandemic period was associated with elevated and fluctuating ARG levels in the urban wastewater system, emphasizing the need for sustained AMR monitoring. These findings address critical knowledge gaps in environmental AMR surveillance and support the integration of WBE into public health strategies aimed at mitigating AMR dissemination.

Semantics

Original Article