Abstract
The discharge of untreated hospital and domestic wastewater into receiving water bodies is still a prevalent practice in developing countries. Unfortunately, because of an ever-increasing population of people who are perennially under medication, these wastewaters contain residues of antibiotics and other antimicrobials as well as microbial shedding, the direct and indirect effects of which include the dissemination of antibiotic resistance genes and an increase in the evolution of antibiotic-resistant bacteria that pose a threat to public and environmental health. This study assessed the taxonomic and functional profiles of bacterial communities, as well as the antibiotic concentrations in untreated domestic wastewater (DWW) and hospital wastewater (HWW), using high-throughput sequencing analysis and solid-phase extraction coupled to Ultra-high-performance liquid chromatography Mass Spectrometry (UHPLC–MS/MS) analysis, respectively. The physicochemical qualities of both wastewater systems were also determined. The mean concentration of antibiotics and the concentrations of Cl−, F− and PO43 were higher in HWW samples than in DWW samples. The phylum Firmicutes was dominant in DWW with a sequence coverage of 59.61% while Proteobacteria was dominant in HWW samples with a sequence coverage of 86.32%. At genus level, the genus Exiguobacterium (20.65%) and Roseomonas (67.41%) were predominant in DWW and HWW samples, respectively. Several pathogenic or opportunistic bacterial genera were detected in HWW (Enterococcus, Pseudomonas and Vibrio) and DWW (Clostridium, Klebsiella, Corynebacterium, Bordetella, Staphylocccus and Rhodococcus) samples. Functional prediction analysis indicated the presence of beta-lactam resistance, cationic antimicrobial peptide (CAMP) resistance and vancomycin resistance genes in HWW samples. The presence of these antibiotic resistance genes and cassettes were positively correlated with the presence of pathogens. These findings show the risk posed to public and environmental health by the discharge of untreated domestic and hospital wastewaters into environmental water bodies.
Highlights
Wastewater originates from various anthropogenic sources including mining and agricultural activities, as well as domestic, industrial, and hospital effluents [1,2]
Compared to domestic wastewater (DWW) effluents, hospital wastewater (HWW) effluents contain, in addition to organic load, high concentrations of disinfectants, microbial shedding as well as partially metabolised antibiotics and other pharmaceuticals originating from patient excrement [1,4,5]
The recorded pH values did not deviate from the World Health Organization (WHO) pH tolerance limit of between 6.00–9.00 for wastewater to be discharged into streams and rivers
Summary
Wastewater originates from various anthropogenic sources including mining and agricultural activities, as well as domestic, industrial, and hospital effluents [1,2]. There still remain loopholes in the regulation and use of antibiotics in many developing countries, including India, where these drugs are still available over the counter without a doctor’s prescription [4,5,6] This escalates the evolution and spread of resistant pathogenic bacterial strains in the given ecosystem [7,8]. The selection for antibiotic resistance has broad epidemiological consequences [14], in terms of an accelerated rate of evolution of multiple drug/antibiotic resistant bacteria, as it runs in the face of a decelerated rate of discovery of novel antibiotics This poses a significant public and environmental health ticking time-bomb that humanity cannot any longer afford to sit and watch unravel
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