There is increasing attention toward factors that potentially contribute to antibiotic resistance (AR), as well as an interest in exploring the emergence and occurrence of antibiotic resistance bacteria (ARB). We monitored six ARBs that cause hospital outbreaks in wastewater influent to highlight the presence of these ARBs in the general population. We analyzed wastewater samples from a municipal wastewater treatment plant (MWWTP) and hospital wastewater (HW) for six species of ARB: Carbapenem-resistant Enterobacteria (CARBA), extended-spectrum 尾-lactamase producing Enterobacteria (ESBL), multidrug-resistant Acinetobacter (MDRA), multidrug-resistant Pseudomonas aeruginosa (MDRP), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococci (VRE). We registered a high percentage of ARBs in MWWTP samples (>66%) for all ARBs except for MDRP, indicating a high prevalence in the population. Percentages in HW samples were low (<78%), and no VRE was detected throughout the study. CARBA and ESBL were detected in all wastewater samples, whereas MDRA and MRSA had a high abundance. This result demonstrated the functionality of using raw wastewater at MWWTP to monitor the presence and extent of ARB in healthy populations. This kind of surveillance will contribute to strengthening the efforts toward reducing ARBs through the detection of ARBs to which the general population is exposed.
Disease outbreaks attributed to monsoon flood-induced pathogen exposure are frequently reported, especially in developing cities with poor sanitation. Contamination levels have been monitored in past studies, yet the sources, routes, and extents of contamination are not always clear. We evaluated pollution from municipal wastewater (MWW) discharge and investigated fecal contamination by Escherichia coli (E. coli) in three agricultural fields on the outskirts of Hue City, Vietnam. After E. coli concentration was determined in irrigation water (IRW), MWW, soil, vegetables (VEG), and manure, its dispersion from MWW was tracked using multilocus sequence typing (MLST) and phylogenetic analyses during the wet and dry seasons. IRW was severely contaminated; 94% of the samples were positive with E. coli exceeding the stipulated standards, while VEG contamination was very low in both seasons. The confirmed total number of isolates was comparable between the seasons; however, results from MLST and phylogenetic clustering revealed more links between the sites and samples to MWW during the wet season. The wet season had four mixed clusters of E. coli isolates from multiple locations and samples linked to MWW, while only one mixed cluster also linking MWW to IRW was observed during the dry season. The most prevalent sequence type (ST) complex 10 and two others (40 and 155) have been associated with disease outbreaks, while other STs have links to major pathotypes. Irrigation canals are significant routes for E. coli dispersion through direct links to the urban drainage-infested river. This study clarified the genotype of E. coli in Hue city, and the numerous links between the samples and sites revealed MWW discharge as the source of E. coli contamination that was enhanced by flooding.
Changes in dissolved organic matter (DOM) characteristics were investigated in two mountainous streams with closed-type sabo dams. Surface water was collected from four stations along the two mountainous streams and analyzed using ultraviolet-visible spectrophotometry and excitation-emission fluorescence matrix (EEM) methods. Optical properties of DOM indicated an increase in molecular weight and aromaticity at stations near the sabo dams. Average spectral ratio values were low before and after the dam (i.e., < 0.72) compared to other sections of the stream. Specific ultraviolet absorbance (SUVA) increased in the vicinities of the dams. While chromophoric DOM characteristics from two sites were influenced by the dam, fluorescence components, however, did not show notable changes around dams. Instead, the three chromophoric components distinguished by EEM-parallel factor analysis, that is, humic-like (C1 and C2) and protein-like (C3) increase along the stream. Fulvic-like component (C1) had a high fluorescence intensity at all stations; all the three components were more abundant in the downstream section. Chromophoric DOM properties varied along the stream based on alterations in molecular size and aromaticity. Using multivariate analysis, the studied sites were grouped into three clusters related to sabo dams and other activities. We conclude that sabo dams modify DOM characteristics which influence the behavior of DOM transported along the stream.
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