Bacterial Concentrations and Water Turbulence Influence the Importance of Conjugation Versus Phage-Mediated Antibiotic Resistance Gene Transfer in Suspended Growth Systems

Antibiotic resistance genes (ARGs) are commonly detected in the atmosphere, but questions remain regarding their sources and relative contributions, bacterial hosts, and corresponding human health risks. Here, we conducted a qPCR- and metagenomics-based investigation of inhalable fine particulate matter (PM2.5) at a large wastewater treatment plant (WWTP) and in the ambient air of Hong Kong, together with an in-depth analysis of published data of other potential sources in the area. PM2.5 was observed with increasing enrichment of total ARGs along the coastal–urban–WWTP gradient and clinically relevant ARGs commonly identified in urban and WWTP sites, illustrating anthropogenic impacts on the atmospheric accumulation of ARGs. With certain kinds of putative antibiotic-resistant pathogens detected in urban and WWTP PM2.5, a comparable proportion of ARGs that co-occurred with MGEs was found between the atmosphere and WWTP matrices. Despite similar emission rates of bacteria and ARGs within each WWTP matrix, about 11–13% of the bacteria and >57% of the relevant ARGs in urban and WWTP PM2.5 were attributable to WWTPs. Our study highlights the importance of WWTPs in disseminating bacteria and ARGs to the ambient air from a quantitative perspective and, thus, the need to control potential sources of inhalation exposure to protect the health of urban populations.

Section: Co-occurrence Patterns Of Args Mges and Potentialmentioning

confidence: 99%

Inhalable Antibiotic Resistome from Wastewater Treatment Plants to Urban Areas: Bacterial Hosts, Dissemination Risks, and Source Contributions

Xie

Liu

et al. 2022

“…Consequently, such an environmental resistome can be transferred to animals and humans directly upon acute exposure to resistome-contaminated water or indirectly through consumption of a resistome-contaminated plant microbiome, thereby constituting a significant risk to “One Health”, an approach comprising both human, environmental, and animal health. Nevertheless, the conjugation efficiency is highly dependent on bacteria density and water turbulence . Therefore, the impact of TCS-mediated plasmid conjugation in WWTP downstream might be less than within the plant, due to the dilution effects on bacteria density and TCS concentration.…”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, the conjugation efficiency is highly dependent on bacteria density and water turbulence. 48 Therefore, the impact of TCS-mediated plasmid conjugation in WWTP downstream might be less than within the plant, due to the dilution effects on bacteria density and TCS concentration.…”

Section: Tcs Expands Transconjugant Pools and Mediates Plasmidmentioning

confidence: 99%

Triclosan Promotes Conjugative Transfer of Antibiotic Resistance Genes to Opportunistic Pathogens in Environmental Microbiome

Ding

et al. 2022

Although triclosan, as a widely used antiseptic chemical, is known to promote the transmission of antibiotic resistance to diverse hosts in pure culture, it is still unclear whether and how triclosan could affect the transmission of broad-host-range plasmids among complex microbial communities. Here, bacterial culturing, fluorescence-based cell sorting, and high-throughput 16S rRNA gene amplicon sequencing were combined to investigate contributions of triclosan on the transfer rate and range of an IncP-type plasmid from a proteobacterial donor to an activated sludge microbiome. Our results demonstrate that triclosan significantly enhances the conjugative transfer of the RP4 plasmid among activated sludge communities at environmentally relevant concentrations. High-throughput 16S rRNA gene sequencing on sorted transconjugants demonstrates that triclosan not only promoted the intergenera transfer but also the intragenera transfer of the RP4 plasmid among activated sludge communities. Moreover, triclosan mediated the transfer of the RP4 plasmid to opportunistic human pathogens, for example, Legionella spp. The mechanism of triclosan-mediated conjugative transfer is primarily associated with excessive oxidative stress, followed by increased membrane permeability and provoked SOS response. Our findings offer insights into the impacts of triclosan on the dissemination of antibiotic resistance in the aquatic environmental microbiome.

“…The collision frequency among ARGs (f-eARG and a-eARG) and the recipient was estimated using collision theory to determine the interaction frequency during transformation experiments. The collision theory has been previously used to assess the interaction frequency between DNA donors and recipients during a horizontal gene transfer . The collision frequency is calculated using eq . Z = π false( r 1 + r 2 false) 2 u C 1 C 2 t 0.25em where Z is the collision frequency of ARGs and the recipient, and r 1 and r 2 are the radius of the DNA and recipient.…”

Section: Methodsmentioning

confidence: 99%

“…The collision theory has been previously used to assess the interaction frequency between DNA donors and recipients during a horizontal gene transfer. 31 The collision frequency is calculated using eq 1.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Chlorination (but Not UV Disinfection) Generates Cell Debris that Increases Extracellular Antibiotic Resistance Gene Transfer via Proximal Adsorption to Recipients and Upregulated Transformation Genes

Yuan

Cheng

et al. 2022

Self Cite

To advance the understanding of antibiotic resistance propagation from wastewater treatment plants, it is important to elucidate how different effluent disinfection processes affect the dissemination of predominantly extracellular antibiotic resistance genes (eARGs). Here, we show that, by facilitating proximal adsorption to recipient cells, bacterial debris generated by chlorination (but not by UV irradiation) increases the natural transformation frequency of their adsorbed eARG by 2.9 to 7.2fold relative to free eARGs. This is because chlorination increases the bacterial surface roughness by 1.1 to 6.7-fold and the affinity toward eARGs by 1.6 to 5.8-fold, and 98% of the total eARGs released after chlorination were adsorbed to cell debris. In contrast, UV irradiation released predominantly free eARGs with 18% to 56% lower transformation frequency. The collision theory indicates that the ARG donor−recipient collision frequency increased by 35.1-fold for eARGs adsorbed onto chlorination-generated bacterial debris, and the xDLVO model infers a 29% lower donor−recipient contact energy barrier for these ARGs. Exposure to chlorinationgenerated bacterial debris also upregulated genes associated with natural transformation in Vibrio vulnificus (e.g., tfoX encoding the major activator of natural transformation) by 2.6 to 5.2-fold, likely due to the generation of chlorinated molecules (5.1-fold higher Cl content after chlorination) and persistent reactive species (e.g., carbon-centered radicals) on bacterial debris. Increased proximal eARG adsorption to bacterial debris was also observed in the secondary effluent after chlorination; this decreased eARG decay by 64% and increased the relative abundance of ARGs by 7.2-fold. Overall, this study highlights that different disinfection approaches can result in different physical states of eARGs that affect their resulting dissemination potential via transformation.