Browsing by Author "Alvarez, Pedro J. J."

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    Global Increase of Antibiotic Resistance Genes in Conjugative Plasmids
    (American Society for Microbiology, 2023) Wang, Xiaolong; Zhang, Hanhui; Long, Xiang; Xu, Ximing; Ren, Hongqiang; Mao, Daqing; Alvarez, Pedro J. J.; Luo, Yi
    Antibiotic resistance is propagating worldwide, but the predominant dissemination mechanisms are not fully understood. Here, we report that antibiotic resistance gene (ARG) abundance in conjugative plasmids that are recorded in the National Center for Biotechnology Information (NCBI) RefSeq plasmid database is increasing globally, which is likely a key factor in the propagation of resistance. ARG abundance in plasmids increased by 10-fold on a global scale from the year 2000 to the year 2020 (from 0.25 to 2.93 ARG copies/plasmid), with a more pronounced increase being observed in low-to-middle income countries. This increasing trend of plasmid-borne ARGs was corroborated by bootstrap resampling from each year of the NCBI RefSeq plasmid database. The results of a correlation analysis imply that if antibiotic consumption keeps growing at the current rates, a 2.7-fold global increase in the ARG abundance of clinically relevant plasmids may be reached by 2030. High sequence similarities of clinically relevant, conjugative plasmids that are isolated both from clinics and from the environment raise concerns about the environmental resistome serving as a potential ARG maintenance reservoir that facilitates transmission across these ecological boundaries. IMPORTANCE Antibiotic resistance propagation is a significant concern due to its projected impacts on both global health and the economy. However, global propagation mechanisms are not fully understood, including regional and temporal trends in the abundance of resistance plasmids that facilitate antibiotic resistance gene (ARG) dissemination. This unprecedented study reports that ARG abundance in the conjugative plasmids that are recorded in the National Center for Biotechnology Information (NCBI) database and harbor ARGs is increasing globally with antibiotic consumption, especially in low-to-medium income countries. Through network and comparative genomic analyses, we also found high sequence similarities of clinically relevant conjugative resistance plasmids that were isolated from clinical and environmental sources, suggesting transmission between these ecological boundaries. Therefore, this study informs the One Health perspective to develop effective strategies by which to curtail the propagation of plasmid-borne antibiotic resistance.
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    Mechanistic insights on the merits and limitations of advanced treatment processes for removal of contaminants of emerging concern
    (2020-08-10) Javed, Hassan; Alvarez, Pedro J. J.
    Perfluoroalkyl substances (PFASs) are recalcitrant contaminants of emerging concern that have widespread distribution in water sources, and exhibit potential to persist and bioaccumulate. Non-destructive and destructive remediation strategies have been actively investigated to remove PFAS. Adsorption on activated carbon is the most widely used non-destructive treatment method to remove PFAS. However, limited innovation has occurred in the field of activated carbon materials and there is a need to develop ultra-high surface area activated materials that exhibit high adsorption capacity and selectivity for target contaminants. Furthermore, non-destructive methods only transfer the contamination from one phase to another and therefore must be used in conjunction with destructive treatment methods to effectively remove and mineralize the target contaminant. In recent years, there has been growing interest to use Advanced Oxidation Processes (AOPs) to degrade PFAS. However, progress in the field has been hampered by the ambiguity that exists regarding the role of two key reactive oxygen species (ROS) i.e. hydroxyl radical (•OH) and superoxide radical anion (O2•-) in degrading PFAS with some studies demonstrating their effectiveness while others claiming the contrary. This dissertation aims to provide mechanistic insights into the treatment of PFAS and other contaminants of emerging concern by: i) Developing fundamental understanding of how the structure of a novel ultra-high surface area activated carbon relates to its function as an adsorbent. ii) Resolving the ambiguity regarding the role of •OH and O2•- in degrading PFAS.
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    Point-of-use filtration units as drinking water distribution system sentinels
    (Springer Nature, 2024) Bai, Weiliang; Xu, Ruizhe; Podar, Mircea; Swift, Cynthia M.; Saleh, Navid B.; Löffler, Frank E.; Alvarez, Pedro J. J.; Kumar, Manish
    Municipal drinking water distribution systems (DWDSs) and associated premise plumbing (PP) systems are vulnerable to proliferation of opportunistic pathogens, even when chemical disinfection residuals are present, thus presenting a public health risk. Monitoring the structure of microbial communities of drinking water is challenging because of limited continuous access to faucets, pipes, and storage tanks. We propose a scalable household sampling method, which uses spent activated carbon and reverse osmosis (RO) membrane point-of-use (POU) filters to evaluate mid- to long-term occurrence of microorganisms in PP systems that are relevant to consumer exposure. As a proof of concept, POU filter microbiomes were collected from four different locations and analyzed with 16S rRNA gene amplicon sequencing. The analyses revealed distinct microbial communities, with occasional detection of potential pathogens. The findings highlight the importance of local, and if possible, continuous monitoring within and across distribution systems. The continuous operation of POU filters offers an advantage in capturing species that may be missed by instantaneous sampling methods. We suggest that water utilities, public institutions, and regulatory agencies take advantage of end-of-life POU filters for microbial monitoring. This approach can be easily implemented to ensure drinking water safety, especially from microbes of emerging concerns; e.g., pathogenic Legionella and Mycobacterium species.