Introduction
The role of the environment as a reservoir for antimicrobial resistance (AMR) is increasingly recognised, with a growing evidence base for its relevance to human health. The presence of antibiotics, alongside other key resistance-driving chemicals (i.e. herbicides, pesticides and human medications) in aquatic environments promotes horizontal gene transfer and alters microbial communities, contributing to the dissemination of antimicrobial-resistance genes, posing downstream risks to human, animal, and ecological health. Currently there is a paucity of evidence on the occurrence and presence of antibiotics in rivers from urban sub-Saharan African settings; locations which are globally highlighted as hotspots of AMR.
Methods
Between February 2020 and October 2020, n=12 polar organic chemical integrative samplers (POCIS) were situated at 5 urban river sites in Blantyre, southern Malawi. POCIS samplers were retrieved from the rivers, extracted using standard procedures and chemical analysis was performed using liquid chromatography coupled with tandem mass spectrometry. Instrumental limits of quantification were calculated using published methods and antibiotic concentrations (ng/POCIS/day) were determined. Statistical analysis and visualisations were performed in R.
Results
In total, 20 antibiotics [3 beta-lactams (CLX, CFX, CXM), 7 sulphonamides (SFD, SFT, SMX, SMI, SPY, NA4, STZ), 4 macrolides (AZM, ARY, CLR, CLS), 1 licosamide (CLI) 1 nitroimidazole (ORN) and 4 others (CHL, MET, RIF, TRI)] were found in urban rivers. Antimicrobial recovery differed spatially and temporally with elevated concentrations (ng/POCIS/day) seen for a range of antimicrobials in urban river systems. The antibiotics with the highest concentrations were sulfamethoxazole (its metabolite NA4) and trimethoprim illustrating the ecological importance of contamination with co-trimoxazole; a drug prescribed locally for treatment and prevention of bacterial disease which remains highly conserved, passing through humans and persisting in the environment.
Discussion
This One Health study describes the broad contamination of urban river systems in Malawi with high concentrations of antibiotics used in human health and provides a unique insight into the riverine drivers of AMR in sub-Saharan Africa. We highlight that in these settings, a paucity of water, sanitation and hygiene (WASH) infrastructure leads to widespread dispersal of antibiotics and resistance-driving chemicals into local river waters. These findings support the need for improved surveillance and further research into the impact of continual levels of resistance driving chemicals on AMR in aquatic environments in these settings.
Conclusion
This data illustrates the importance of adopting a One Health approach to AMR surveillance and provides baseline metrics for future AMR surveillance and antibiotic usage targets. Additionally, we highlight the importance of targeted WASH interventions designed to interrupt AMR within these settings.