Domestic refrigerators: An overlooked breeding ground of antibiotic resistance genes and pathogens

Prevalence of antibiotics, antibiotic resistance genes, and their associations in municipal wastewater treatment plants along the Yangtze River basin, China

The overuse and misuse of antibiotics have resulted in the pollution of antibiotics and antibiotic resistance genes (ARGs) in municipal wastewater treatment plants (WWTPs), posing threats to ecological security and human health. Thus, a comprehensive investigation was conducted to assess the occurrence, removal efficiency, and ecological risk of antibiotics, along with the diversity, abundance, and co-occurrence of ARGs, and their correlations in 13 WWTPs along the Yangtze River Basin. Among 35 target antibiotics, 23 antibiotics within 6 categories were detected in all the samples. Amoxicillin (AMO), ofloxacin (OFL), and pefloxacin (PEF) were predominant in influents, while AMO exhibited dominance with the highest concentration of 1409 ng/L in effluents. Although antibiotic removal performance varied among different WWTPs, a significant decrease in each antibiotic category and overall antibiotics was observed in effluents compared with that in influents (p < 0.05). Remarkably, ecological risk assessment revealed high risks associated with AMO and ciprofloxacin (CIP) and medium risks linked to several antibiotics, notably including OFL, roxithromycin (ROX), clarithromycin (CLA), and tetracycline (TC). Furthermore, 96 ARG subtypes within 12 resistance types were detected in this study, and the total absolute abundance and diversity of ARGs were significantly decreased from influents to effluents (p < 0.05). Enrichment of 38 ARGs (e.g., blaNDM, ermA, vatA, mexA, and dfrA25) in effluents indicated potential health risks. Various mobile genetic elements (MGEs), exhibited significant correlations with a majority of ARGs in both influents and effluents, such as intⅠ1, tnpA1, tnpA5, and tp614, underscoring the important role of MGEs in contributing to the ARG dissemination. Many antibiotics displayed lower correlations with corresponding ARGs, but exhibited higher correlations with other ARGs, suggesting complex selective pressures influencing ARG propagation. Overall, the incomplete elimination of antibiotics and ARGs in WWTPs is likely to pose adverse impacts on aquatic ecosystems in the Yangtze River Basin.

Bacterial Contamination in the Different Parts of Household Washing Machine: New Insights from Chengdu, Western China

The moist and warm environment in the household washing machine provides ideal living conditions for the growth and survival of various microorganisms. However, the biodiversity of bacterial community in the different parts of washing machine from Chinese households has not been clarified. In this study, we assessed the bacterial communities in sealing strip, detergent drawer, inner drum, water filter and greywater of ten domestic washing machines quantitatively and qualitatively in Chengdu, southwestern China. The microbial cultivation results indicated that the washing machines from Chengdu had a severe microbial contamination reflected by large counts on bacteria, fungi and coliform. Furthermore, the sequencing data showed that the different parts displayed distinctive bacterial compositions. At the level of genus, the anaerobic bacteria of Caproiciproducens and Acidipropionibacterium were predominant in sealing strip. Barnesiella, Shinella and Sellimonas were detected as the characteristic bacteria in detergent drawer. The pathogens of Luteibacter and Corynebacterium at the genus level were the dominant bacteria in inner drum and water filter, respectively. The genera of Azospira, Roseococcus, Elstera and Aquicella, which belonged to the pathogenic phylum of Proteobacteria, were identified as bioindicators for the greywater. Gene function analysis on the sequencing data illustrated that the bacteria from washing machines were potentially associated with bacterial infectious diseases and antimicrobial resistance. This study shows the bacterial diversity in the different parts of washing machines, providing new clues for bacterial contamination in washing machines from Chinese households.

Long-term field application of manure induces deep selection of antibiotic resistomes in leaf endophytes of Chinese cabbage

Antibiotic resistomes in leaf endophytes of vegetables threaten human health through the food chain. However, little is known about the ability of long-term manure fertilization to impact the deep selection of antibiotic resistance genes (ARGs) in leaf endophytes of vegetables planted in different types of soils. Here, by high-throughput quantitative PCR, we characterized the ARGs of leaf endophytes of Chinese cabbage (Brassica pekinensis (Lour.) Rupr.) grown in long-term (14 year) manure-amended acidic, neutral and calcareous soils. In total, 87 ARGs and 4 mobile genetic elements (MGEs) were detected in all the samples. Manure fertilization significantly increased the ARG numbers and normalized abundance in leaf endophytes, especially in acidic soil. Moreover, in acidic soil, manure application also led to a higher increase in the normalized abundance of opportunist and specialist ARGs, and more opportunist and specialist ARGs posed a high risk according to their risk ranks. Random forest analysis revealed that Proteobacteria and MGEs were the major drivers affecting the normalized abundance of opportunist and specialist ARGs in both acidic and neutral soils, respectively. In calcareous soil, Cyanobacteria and Actinobacteria were the most important contributors. Collectively, this study expands our knowledge about the deep selection of plant resistomes under long-term manure application.