Hospital Effluents Are One of Several Sources of Metal, Antibiotic Resistance Genes, and Bacterial Markers Disseminated in Sub-Saharan Urban Rivers

Abstract

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 (blaTEM, blaCTX-M, blaSHV, 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 blaTEM) and FIB and Psd 0.57 < r < 0.82 (p < 0.001, n = 65); and (iii) ARGs (except blaTEM) 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.

Accumulation of toxic metals and organic micro-pollutants in sediments from tropical urban rivers, Kinshasa, Democratic Republic of the Congo

“…The values ranged from 92.6-242.7, 76.5-163.2, 67.4-89.8 mg kg -1 for the sites R1, R2, and R3, respectively. The results obtained are in agreement with our previous studies, which demonstrated that there are large variations in the distribution of TC, TN, TP and grain size in sediments from some urban rivers located in the city of Kinshasa (Mubedi et al, 2013;Tshibanda et al, 2014;Kilunga et al, 2016;Laffite et al, 2016).…”

“…The discharge of untreated urban effluents into river environments is a major concern in developing countries. Given this fact, in recent years accumulation of heavy metals in river sediments from developing countries have been reported with more attention (Mubedi et al, 2013;Devarajan et al, 2015b;Tamim et al, 2016;Laffite et al, 2016). Hydrophobic organic compounds (HOCs), such as PAHs, PCBs, and OCPs have been identified as environmental pollutants in all environmental compartments (Wu et al, 1999).…”

“…These rivers serve as sources of recreational use, bathing, drinking water supply and irrigation for urban agriculture. A very few comprehensive studies of heavy metals, pesticides and POPs in Congo River Basin have been conducted (Verhaert et al, 2013;Mwanamoki et al 2014b;2015;Laffite et al, 2016). These studies recommended further researches in the urban river receiving systems in studied area to evaluate the quality of the aquatic ecosystem.…”

A survey of extended-spectrum beta-lactamase-producing Enterobacteriaceae in urban wetlands in southwestern Nigeria as a step towards generating prevalence maps of antimicrobial resistance

“…Isolation of bla CTX-M containing strains from samples taken in November 2014, December 2014 and January 2015 together with amplification in standard PCR demonstrated that microbes harboring this gene were present at Awba at several time points. The absolute and relative abundances of bla CTX-M-1 measured at the site were similar to that reported for the sediment of Lake Brêt, Switzerland [81], an urban river in Kinshasa, Democratic Republic of Congo [82], and in waste water treatments plants and urban wetlands in the United States [83], but slightly lower than that measured in a river receiving hospital effluents in Tamil Nadu, India [84]. In all of those studies primers targeting Group 1 bla CTX-M were used.…”

Co‐selection for antibiotic resistance genes is induced in a soil amended with zinc

“…Previous work has also suggested that the increased relative abundance of intI1 could enhance the potential for HGT of ARGs and has a strong positive correlation with the Zn content in activated sludge bioreactors (Peltier et al, 2010). In addition, heavy metal and antibiotic resistance are frequently linked on the same plasmid (Baker-Austin, Wright, Stepanauskas, & McArthur, 2006;Laffite et al, 2016), and increased mobilization under metal selective stress might increase the possibility of ARGs spreading to human pathogenic bacteria (Zhu et al, 2013).…”