RESUMEN
As antimicrobial resistance continues to pose a significant threat to global health, this study provided a focused examination of the prevalence and behavior of key antibiotic resistance genes in aquatic environments. We investigated the quantitative distribution of intI1, sul1, blaTEM, blaNDM, blaVIM, mcr-1, tetQ, and crAssphage within wastewater influents (n = 12), effluents (n = 12) and river water samples (n = 12), from three municipal wastewater treatment plants and three river locations in an urbanized watershed in Central Thailand over dry and wet seasons. The qPCR method demonstrated that intI1, sul1, blaTEM, and tetQ were the most abundant in all samples (2.71-7.89 mean log10 copies/100 mL), with all genes exhibiting consistently uniform levels across diverse locations, suggesting the potential for any site to act as a monitoring sentinel. Although there is a significant reduction of ARG concentrations by WWTPs (0.62 - >4.05 LRV), the persistence of these genes in effluents points to the limited effectiveness of existing treatment methodologies. Temporal data indicated stable ARG concentrations over time, but tetQ levels rose during the wet season, in alignment with the monsoonal climate in Thailand. Additionally, we identified crAssphage, a marker of human sewage contamination, exhibited strong correlations with the more abundant ARGs (rho 0.65 - 0.81), implying that human waste contributes significantly to the environmental burden of ARGs. The results of this research highlight the widespread nature of ARGs in water systems and the need for improved treatment and sanitation strategies to mitigate the public health threat posed by antimicrobial resistance.
RESUMEN
Hospital wastewater is a major hotspot for the spread of antimicrobial resistance (AMR) in aquatic ecosystems. This study aimed to investigate the prevalence of antibiotic resistance genes (ARGs) and their correlation with crAssphage in a hospital wastewater treatment plant (HWWTP) and a receiving canal. Water samples were analyzed for 94 ARGs and crAssphage relative to the 16S rRNA using high-throughput quantitative polymerase chain reaction (HT-qPCR). Subsequently, 7 ARGs and crAssphage were selected and quantified using qPCR. The results showed that the detected genes ranged from 79 to 93 out of 95 genes. The raw wastewater (WW) samples had the highest gene diversity compared to the upstream canal, which had less diversity than downstream samples, as determined by HT-qPCR. The blaGES was the most abundant in WW samples, while qacEΔ1, merA, IS6100, tnpA, and IS26 showed high prevalence throughout the treatment processes. The concentrations of intI1, sul1, blaTEM,blaNDM,blaVIM,tetQ, mcr-1, crAssphage, and 16S rRNA, measured using qPCR, were the highest in WW and significantly reduced in treated water samples. Although some water quality parameters, such as total suspended solids and dissolved oxygen, did not significantly differ before and after treatment, removal efficiency ranged from 0.60 to 3.23 log reduction values (LRV). The highest LRV was observed for the tetQ, whereas the mcr-1 had the lowest LRV. Strong positive correlations among the absolute concentrations of ARGs and crAssphage were observed (Spearman's rho = 0.6-1.0), and biochemical oxygen demand correlated with blaTEM and blaVIM (Spearman's rho = 0.6). These results indicate that crAssphage and water quality could reflect the distribution of other ARGs throughout the HWWTP. Further studies are needed to underscore the importance of monitoring ARGs and genetic markers such as crAssphage in HWWTPs and their receiving waters to enhance our understanding of ARG distribution.
RESUMEN
Microbial contamination deteriorates source water quality, posing a severe problem for drinking water suppliers worldwide and addressed by the Water Safety Plan framework to ensure high-quality and reliable drinking water. Microbial source tracking (MST) is used to examine different microbial pollution sources via host-specific intestinal markers for humans and different types of animals. However, the application of MST in tropical surface water catchments that provide raw water for drinking water supplies is limited. We analyzed a set of MST markers, namely, three cultivable bacteriophages and four molecular PCR and qPCR assays, together with 17 microbial and physicochemical parameters, to identify fecal pollution from general, human-, swine-, and cattle-specific sources. Seventy-two river water samples at six sampling sites were collected over 12 sampling events during wet and dry seasons. We found persistent fecal contamination via the general fecal marker GenBac3 (100 % detection; 2.10-5.42 log10 copies/100 mL), with humans (crAssphage; 74 % detection; 1.62-3.81 log10 copies/100 mL) and swine (Pig-2-Bac; 25 % detection; 1.92-2.91 log10 copies/100 mL). Higher contamination levels were observed during the wet season (p < 0.05). The conventional PCR screening used for the general and human markers showed 94.4 % and 69.8 % agreement with the respective qPCR results. Specifically, in the studied watershed, coliphage could be a screening parameter for the crAssphage marker (90.6 % and 73.7 % positive and negative predictive values; Spearman's rank correlation coefficient = 0.66; p < 0.001). The likelihood of detecting the crAssphage marker significantly increased when total and fecal coliforms exceeded 20,000 and 4000 MPN/100 mL, respectively, as Thailand Surface Water Quality Standards, with odds ratios and 95 % confidence intervals of 15.75 (4.43-55.98) and 5.65 (1.39-23.05). Our study confirms the potential benefits of incorporating MST monitoring into water safety plans, supporting the use of this approach to ensure high-quality drinking water supplies worldwide.
