article · Frontiers in Microbiology
Urban aquatic environments in Sub-Saharan Africa face growing risks from emerging biological contaminants and heavy metals. This study analysed sediments collected from four hospital outlet pipes and their receiving river systems in Kinshasa, Democratic Republic of the Congo. Quantitative testing measured concentrations of toxic metals alongside bacterial loads, faecal indicator bacteria, and several antibiotic resistance genes. Hospital outlet sediments contained substantial amounts of toxic metals, including zinc, lead, and copper. Furthermore, elevated copy numbers of antibiotic resistance genes and bacterial markers were detected across all river sampling locations, including sites upstream and downstream of discharge points. These biological contaminants correlated significantly with total bacterial loads, faecal indicator bacteria, and specific toxic metals. The widespread distribution demonstrates that hospital discharges are not the exclusive source, showing that broader urban wastewaters also drive the dissemination of biological contaminants into river networks.
The spread of antibiotic resistance and heavy metals in urban waterways threatens public health and water security. Identifying contamination pathways helps municipal authorities understand how hazardous elements enter community water systems. Because high pollution levels appear throughout urban rivers and not solely near clinics, managing these risks requires comprehensive urban sanitation strategies rather than focusing exclusively on healthcare facilities.
This early-stage environmental study provides foundational evidence that could inform the design of urban wastewater treatment systems, effluent monitoring programmes, and environmental risk assessment tools. Potential end users include municipal water utilities, environmental protection agencies, and sanitation engineers. The abstract describes observational field research rather than an applied tool or process, meaning any commercial or operational application remains at an early concept stage requiring further development.
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Data concerning the occurrence of emerging biological contaminants such as antibiotic resistance genes (ARGs) and fecal indicator bacteria (FIB) in aquatic environments in Sub-Saharan African countries is limited. On the other hand, antibiotic resistance remains a worldwide problem which may pose serious potential risks to human and animal health. Consequently, there is a growing number of reports concerning the prevalence and dissemination of these contaminants into various environmental compartments. Sediments provide the opportunity to reconstruct the pollution history and evaluate impacts so this study investigates the abundance and distribution of toxic metals, FIB, and ARGs released from hospital effluent wastewaters and their presence in river sediments receiving systems. ARGs (bla TEM, bla CTX-M, bla SHV, and aadA), total bacterial load, and selected bacterial species FIB [Escherichia coli, Enterococcus (ENT)] and species (Psd) were quantified by targeting species specific genes using quantitative PCR (qPCR) in total DNA extracted from the sediments recovered from 4 hospital outlet pipes (HOP) and their river receiving systems in the City of Kinshasa in the Democratic Republic of the Congo. The results highlight the great concentration of toxic metals in HOP, reaching the values (in mg kg(-1)) of 47.9 (Cr), 213.6 (Cu), 1434.4 (Zn), 2.6 (Cd), 281.5 (Pb), and 13.6 (Hg). The results also highlight the highest (P < 0.05) values of 16S rRNA, FIB, and ARGs copy numbers in all sampling sites including upstream (control site), discharge point, and downstream of receiving rivers, indicating that the hospital effluent water is not an exclusive source of the biological contaminants entering the urban rivers. Significant correlation were observed between (i) all analyzed ARGs and total bacterial load (16S rRNA) 0.51 to 0.72 (p < 0.001, n = 65); (ii) ARGs (except bla TEM) and FIB and Psd 0.57 < r < 0.82 (p < 0.001, n = 65); and (iii) ARGs (except bla TEM) and toxic metals (Cd, Cr, Cu, and Zn) 0.44 to 0.72, (p < 0.001, n = 65). These findings demonstrate that several sources including hospital and urban wastewaters contribute to the spread of toxic metals and biological emerging contaminants in aquatic ecosystems.
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DOI: 10.3389/fmicb.2016.01128
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