Comparative study on the bacterial diversity and antibiotic resistance genes of urban landscape waters replenished by reclaimed water and surface water in Xi'an, China

A metagenomic study of antibiotic resistance genes in a hypereutrophic subtropical lake contaminated by anthropogenic sources

Antibiotic resistance genes (ARGs) are a major threat to human and environmental health. This study investigated the occurrence and distribution of ARGs in Lake Cajititlán, a hypereutrophic subtropical lake in Mexico contaminated by anthropogenic sources (urban wastewater and runoff from crop and livestock production). ARGs (a total of 475 genes) were detected in 22 bacterial genera, with Pseudomonas (144 genes), Stenotrophomonas (88 genes), Mycobacterium (54 genes), and Rhodococcus (27 genes) displaying the highest frequencies of ARGs. Among these, Pseudomonas aeruginosa and Stenotrophomonas maltophilia showed the highest number of ARGs. The results revealed a diverse array of ARGs, including resistance to macrolides (11.55 %), aminoglycosides (8.22 %), glycopeptides (6.22 %), tetracyclines (4 %), sulfonamides (4 %), carbapenems (1.11 %), phenicols (0.88 %), fluoroquinolones (0.44 %), and lincosamides (0.22 %). The most frequently observed ARGs were associated with multidrug resistance (63.33 %), with MexF (42 genes), MexW (36 genes), smeD (31 genes), mtrA (25 genes), and KHM-1 (22 genes) being the most common. Lake Cajititlán is a recreational area for swimming, fishing, and boating, while also supporting irrigation for agriculture and potentially acting as a drinking water source for some communities. This raises concerns about the potential for exposure to antibiotic-resistant bacteria through these activities. The presence of ARGs in Lake Cajititlán poses a significant threat to both human and environmental health. Developing strategies to mitigate the risks of antibiotic resistance, including improving wastewater treatment, and promoting strategic antibiotic use and disposal, is crucial. This study represents a significant advancement in the understanding of antibiotic resistance dynamics in a hypereutrophic subtropical lake in a developing country, providing valuable insights for the scientific community and policymakers.

Algal or bacterial community: Who can be an effective indicator of the impact of reclaimed water recharge in an urban river

Reclaimed water has been widely utilized for water resource replenishment, yet little is known regarding its impacts on various microorganisms in the receiving water. To address this knowledge gap, we systematically investigated the responses of bacteria and algae to the recharge of reclaimed water by using the high-throughput sequencing technology in the urban Chaobai River. After the inputs of reclaimed water, lower contents of NO2--N, NH4+-N, and TP were observed in the downstream section compared to that of upstream without reclaimed water, indicating that reclaimed water could improve the water quality of the receiving water. Correspondingly, both bacterial and algal communities showed the decreased network complexity in the downstream section, but many common freshwater bacteria and typical bloom-forming algae were dominant in the downstream, potentially suggesting that algae were more sensitive to the local environmental conditions. More importantly, although nitrogen and phosphorus served as the paramount factors in shaping both bacterial and algal communities, environmental selection contributed more to algal rather than bacterial community, and simultaneously algal variations could further affect bacterial dynamics in the urban river. Overall, these findings revealed distinct characteristics of bacteria and algae in responding to the reclaimed water recharge, highlighting the superiority of algae in indicating environmental changes, especially in monitoring and regulating the replenishment of reclaimed water in urban rivers.

New insight into the effect of microplastics on antibiotic resistance and bacterial community of biofilm

Microplastics (MPs) could serve as substrates for microbial colonization and biofilm formation. However, research on the effects of different types of microplastics and natural substrates on biofilm formation and community structure in the presence of antibiotic-resistant bacteria (ARB) is limited. In this study, we employed by means of microcosm experiments to analyze the situation of biofilms conditions, bacterial resistance patterns, antibiotic resistance genes (ARGs) distribution, and bacterial community on different substrates using microbial cultivation, high throughtput sequencing and PCR. The result showed that biofilms on different substrates markedly increased with time, with MPs surfaces formed more biofilm than stone. Analyses of antibiotic resistant showed negligible differences in the resistance rate to the same antibiotic at 30 d, but tetB would be selectively enriched on PP and PET. The microbial communities associated with biofilms on MPs and stones exhibited variations during different stages of formation. Notably, phylum WPS-2 and Epsilonbacteraeota were identified as the dominant microbiomes of biofilms on MPs and stones at 30 d, respectively. Correlation analysis suggested that WPS-2 could potentially be a tetracycline-resistant bacterium, while Epsilonbacteraeota did not correlate with any detected ARB. Our results emphasized the potential threat posed by MPs as attachment carriers for bacteria, particularly ARB, in aquatic environments.

Antimicrobial Resistance Development Pathways in Surface Waters and Public Health Implications

Human health is threatened by antibiotic-resistant bacteria and their related infections, which cause thousands of human deaths every year worldwide. Surface waters are vulnerable to human activities and natural processes that facilitate the emergence and spread of antibiotic-resistant bacteria in the environment. This study evaluated the pathways and drivers of antimicrobial resistance (AR) in surface waters. We analyzed antibiotic resistance healthcare-associated infection (HAI) data reported to the CDC's National Healthcare Safety Network to determine the number of antimicrobial-resistant pathogens and their isolates detected in healthcare facilities. Ten pathogens and their isolates associated with HAIs tested resistant to the selected antibiotics, indicating the role of healthcare facilities in antimicrobial resistance in the environment. The analyzed data and literature research revealed that healthcare facilities, wastewater, agricultural settings, food, and wildlife populations serve as the major vehicles for AR in surface waters. Antibiotic residues, heavy metals, natural processes, and climate change were identified as the drivers of antimicrobial resistance in the aquatic environment. Food and animal handlers have a higher risk of exposure to resistant pathogens through ingestion and direct contact compared with the general population. The AR threat to public health may grow as pathogens in aquatic systems adjust to antibiotic residues, contaminants, and climate change effects. The unnecessary use of antibiotics increases the risk of AR, and the public should be encouraged to practice antibiotic stewardship to decrease the risk.

Distribution characteristics of antibiotic resistance bacteria and related genes in urban recreational lakes replenished by different supplementary water source

The distribution characteristics of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in urban recreational water from different water-supply sources might be different. In this study, water samples were collected to detect the antibiotic resistance of heterotrophic bacteria to five antibiotics, and the content, phenotype, gene type and species distribution of resistant bacteria were analyzed. The results showed that the changes of bacteria resistance rate in two lakes to five kinds of antibiotics were synchronous with time, and it would reach its maximum in autumn. The detection of ARGs and int I in 80 resistance strains showed that the detection rate of tetG, tetA and int I was high. Here, 51.25% of the bacteria were doubly resistant to AMP-CTX. The 80 isolate strains were of nine genera and 19 species, among which Bacillus cereus, Escherichia coli, Aeromonas veronii, Aeromonas caviae and Raoultella ornithinolytica were the common ARB species in two lakes. Correlation analysis showed that the water temperature was significantly correlated with the content of ARB in sulfamethoxazole (SMZ) and cefotaxime (CTX) (p < 0.05), and the total phosphorus (TP) in FQ lake was significantly correlated with the content of AMP-resistant bacteria (p < 0.05), while there were no other correlations between the changes of other water quality indexes and the content of ARB (p > 0.05).