Spatiotemporal urban water profiling for the assessment of environmental and public exposure to antimicrobials (antibiotics, antifungals, and antivirals) in the Eerste River Catchment, South Africa

Antibiotic usage, excretion, and persistence are all important factors in association with the occurrence and dissemination of antimicrobial resistance. Urban water profiling was utilised in the Eerste River catchment (South Africa) to establish antibiotic usage in a catchment where comprehensive prescription records were not readily available and where portions of the community did not have sufficient access to sanitation. This technique enabled the environmental exposure to be quantified throughout the catchment area and the identification of contamination hotspots. Monitoring occurred over a 10-month period. 812 samples were processed using UPLC-MS/MS for the quantitation of 56 antimicrobials and 26 of their metabolites. Spatiotemporal trends were established, with consideration to community behaviour, seasonal changes, and physiochemical properties of the analytes. The Eerste River samples collected upstream from the town of Stellenbosch had the lowest antibiotic loads (< 4 g/day), unafflicted by industrial presence and with only small impact from farming activity. This was followed by sites downstream from a treated wastewater treatment plant (serving 178K people) discharge point (influent: 500-800 g/day and effluent 50-100 g/day), which indicates a high efficiency of wastewater treatment allowing for an effective reduction of ABs and a lower environmental burden compared to the river sites receiving untreated waste from communities in informal settlements (6-12K people) that are not connected to the sewer infrastructure (with AB levels accounting for 100-600 g/day). Temporal trends exhibited reduced daily loads during the summer to early autumn. This is likely due to seasonal patterns in community health. However, weather patterns are also important to consider – particularly for the river sites. South Africa has notable rainfall and temperature seasonality. ARVs, emtricitabine and lamivudine, were the most prevalent drugs throughout the monitoring campaign, followed by tuberculosis drugs and sulfonamides. ARVs were, however, effectively reduced via wastewater treatment processes (>97%). This was also the case for beta-lactams, nitrofurantoin, and trimethoprim. The treatment efficacy for other drugs was more variable, that did not appear to have temporal significance.