No abstract

The occurrence and distribution of 20 subtypes of antibiotic resistance genes (ARGs), conferring sulfonamide, tetracycline, macrolide, β-lactam, aminoglycoside, or quinolone antibiotic resistance, were investigated in urban dust samples collected from the surfaces of three megacities (Beijing, Tianjin, and Shijiazhuang) of northern China. Real-time polymerase chain reaction indicated that the abundance of ARGs and 16S rRNA genes was significantly higher in the summer than in the winter. A total of 80 antibiotic-resistant bacteria were isolated and identified, and 12 of those species were identified as opportunistic pathogens. An isolated pathogen Acinetobacter sp. was proven to be able to transfer antibiotic resistance, which highlights the potential risk that an urban dust-associated ARG poses to public health. Deep 16S rRNA sequencing indicated high heterogeneity of bacterial communities among cities in the summer, but great homogeneity in the winter. In the summer, Enterococcus, Massilia, and Anthrobacter were the most prevalent genera in Tianjin, Beijing, and Shijiazhuang, respectively. However, the most prevalent bacterial genera were Bacillus and Lactococcus in the winter. This is the first study of the occurrence and distribution of the urban dust-associated bacterial community and its associated bacterial antibiotic resistance in northern China. This study highlights the risk of dust-associated antibiotic resistance to public health.

No abstract

The emergence and spread of NDM-1 (New Delhi metallo-β-lactamase-1) are of great concern to public health. Our previous study reported the occurrence and persistence of NDM-1 genes in wastewater treatment plants (WWTPs). In this study, the occurrence and fate of NDM-1 genes and host bacteria were investigated in a WWTP discharge-receiving river. A considerable level of NDM-1 genes occurred in the receiving river, whereas no NDM-1 genes were detected upstream of the WWTP. This finding together with the DNA sequencing of NDM-1 genes demonstrated that the river NDM-1 is derived from the WWTP. Opportunistic pathogens, like Shigella sonnei, Enterococcus faecium, and Wautersiella falsenii, were isolated from both the receiving water and the WWTP. This study underscores the need to mitigate the release of NDM-1 from WWTPs and indicates that more attention should to be paid to the propagation of these genes to the receiving environment to alleviate their worldwide dissemination.

An expanding list of chemicals may permeabilize bacterial cells and facilitate horizontal gene transfer (HGT), which enhances propagation of antibiotic resistance genes (ARGs) in the environment. Previous studies showed that 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), an ionic liquid, can facilitate HGT of some ARGs among bacteria. However, the dynamic response of a wider range of ARGs and associated mobile genetic elements (MGEs) in different environments is unknown. Here, we used metagenomic tools to study shifts of the resistome and microbiome in both sediments and freshwater microcosms exposed to [BMIm][PF6]. Exposure for 16 h to 0.1 or 1.0 g/L significantly enriched more than 207 ARG subtypes primarily encoding efflux pumps in freshwater microcosms as well as cultivable antibioticresistant bacteria. This resistome enrichment was attributed to HGT facilitated by MGEs (428 plasmids, 61 integron-integrase genes, and 45 gene cassettes were enriched) as well as to HGT-related functional genes. Interestingly, resistome enrichment occurred fast (within 16 h) after [BMIm][PF6] exposure, before any significant changes in bacterial community structure. Similar ARG enrichment occurred in sediment microcosms exposed to [BMIm][PF6] for 28 d, and this longer exposure affected the microbial community structure (e.g., Proteobacteria abundance increased significantly). Overall, this study suggests that [BMIm][PF6] releases could rapidly enrich the antibiotic resistome in receiving environments by increasing HGT and fortuitously selecting for efflux pump genes, thus contributing to ARG propagation.

Wild birds are known to harbor and discharge antibiotic-resistant bacteria (ARB) and their associated antibiotic resistance genes (ARGs). However, assessments of their contribution to the dissemination of antibiotic resistance in the environment are limited to culture-dependent bacterial snapshots. Here, we present a high-throughput sequencing study that corroborates extensive ARG exchange between wild bird feces and their habitats and implies the need to scrutinize high-mobility birds as potential vectors for global propagation of ARGs. We characterized the resistome (281 ARGs) and microbiome of seven wild bird species and their terrestrial and aquatic habitats. The resistomes of bird feces were influenced by the microbial community structure, mobile genetic elements (MGEs), and residual antibiotics. We designated 33 ARGs found in more than 90% of the bird fecal samples as core ARGs of wild bird feces, among which 16 ARGs were shared as core ARGs in both wild bird feces and their habitats; these genes represent a large proportion of both the bird feces (35.0 ± 15.9%) and the environmental resistome (29.9 ± 21.4%). One of the most detected β-lactam resistance genes (bla TEM, commonly harbored by multidrug resistant “superbugs”) was used as molecular marker to demonstrate the high interconnectivity of ARGs between the microbiomes of wild birds and their habitats. Overall, this work provides a comprehensive analysis of the wild bird resistome and underscores the importance to consider genetic exchange between animals and the environment in the One Health approach.

No abstract

No abstract