Abundance and Spatial Distribution of Third Generation Cephalosporin Resistant Escherichia coli in Wastewater and impact on the receiving Korle Lagoon, Accra, Ghana

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Abstract
Antimicrobial resistance in the environment is a major public health threat, particularly in low- and middle-income countries where there is inadequate wastewater treatment infrastructure. Third generation cephalosporin resistant Escherichia coli (3GCR E. coli) are of particular concern as they have clinical significance and may spread associated resistance genes in environment. This study quantified 3GCR E. coli in wastewater discharged into the Korle Lagoon in Accra, Ghana, and assessed the influence of these discharges on the lagoon. In a cross-sectional study conducted from November 2023 to October 2024, wastewater and lagoon water samples were collected monthly from four discharge points (the Korle Bu Teaching Hospital (KBTH) mortuary drain, the Korle Bu wastewater pumping station, the Mudor Wastewater Treatment Plant and the Lavender Hill Faecal Treatment Plant) and from paired upstream and downstream lagoon sites at each point. Isolates were enumerated by membrane filtration on a selective chromogenic medium, confirmed by MALDI-TOF mass spectrometry, and tested for antimicrobial susceptibility in accordance with CLSI (2024) guidelines. Counts were highest in overflow wastewater from the Korle Bu pumping station (median 3.75 × 10⁶ CFU/100 mL) and in Mudor effluent (1.24 × 10⁶ CFU/100 mL) and differed significantly across sampling sites (Kruskal-Wallis H = 19.6, p = 0.003). Paired comparisons consistently showed higher counts downstream than upstream of the discharge points, most markedly at the KBTH mortuary drain (4.03 × 10⁵ versus 2.36 × 10⁵ CFU/100 mL; p = 0.018) and the Korle Bu pumping station overflow (p = 0.012). The elevated downstream burden indicates active dissemination of resistant 3GCR E. coli along the lagoon continuum. These findings underscore the urgent need to upgrade wastewater treatment infrastructure and to integrate AMR surveillance within wastewater systems in Ghana.