Antibiotic Resistance Gene-Carrying Plasmid Spreads into the Plant Endophytic Bacteria using Soil Bacteria as Carriers.

Applications of animal manure and treated wastewater could enrich antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the plant microbiome. However, the mechanistic studies of the transmission of ARB and ARGs from the environment to plant endophytic bacteria were few. Herein, a genetically engineered fluorescent Escherichia coli harboring a conjugative RP4 plasmid that carries three ARGs was used to trace its spread into Arabidopsis thaliana interior in a tetracycline-amended hydroponic system in the absence or presence of a simulated soil bacterial community. Confocal microscope observation demonstrated that E. coli was internalized into plant tissues and the carried RP4 plasmid was transferred into plant endophytic bacteria. More importantly, we observed that soil bacteria inhibited the internalization of E. coli but substantially promoted RP4 plasmid spread into the plant microbiome. The altered RP4-carrying bacterial community composition in the plant microbiome and the increased core-shared RP4-carrying bacteria number between plant interior and exterior in the presence of soil bacteria collectively confirmed that soil bacteria, especially Proteobacteria, might capture RP4 from E. coli and then translocate into plant microbiome, resulting in the increased RP4 plasmid spread in the plant endophytes. Overall, our findings provided important insights into the dissemination of ARB and ARGs from the environment to the plant microbiome.

Long-term spatiotemporal variation of antimicrobial resistance genes within the Serratia marcescens population and transmission of S. marcescens revealed by public whole-genome datasets.

The development of antimicrobial resistance (AMR) is accelerated by the selective pressure exerted by the widespread use of antimicrobial drugs, posing an increasing danger to public health. However, long-term spatiotemporal variation in AMR genes in microorganisms, particularly in bacterial pathogens in response to antibiotic consumption, is not fully understood. Here, we used the NCBI RefSeq database to collect 478 whole-genome sequences for Serratia marcescens ranging from 1961 up to 2019, to document global long-term AMR trends in S. marcescens populations. In total, 100 AMR gene subtypes (16 AMR gene types) were detected in the genomes of S. marcescens populations. We identified 3 core resistance genes in S. marcescens genomes, and a high diversity of AMR genes was observed in S. marcescens genomes after corresponding antibiotics were discovered and introduced into clinical practice, suggesting the adaptation of S. marcescens populations to challenges with therapeutic antibiotics. Our findings indicate spatiotemporal variation of AMR genes in S. marcescens populations in relation to antibiotic consumption and suggest the potential transmission of S. marcescens isolates harboring AMR genes among countries and between the environment and the clinic, representing a public health threat that necessitates international solidarity to overcome.

Study of the micro-climate and bacterial distribution in the deadspace of N95 filtering face respirators.

It is common for people to use N95 filtering facepiece respirators (FFRs) in daily life, especially in locations where particulate matter (PM2.5) concentration is rising. Wearing N95 FFRs is helpful to reduce inhalation of PM2.5. Although N95 FFRs block at least 95% of particles from the atmosphere, the deadspace of N95 FFRs could be a warm, wet environment that may be a perfect breeding ground for bacterial growth. This work studies the micro-climate features including the temperature distribution and water vapor condensation in the deadspace of an N95 FFR using the computational fluid dynamics (CFD) method. Then, the temperature and relative humidity inside the same type of N95 FFR are experimentally measured. There is a good agreement between the simulation and experimental results. Moreover, an experiment is conducted to study the distribution of bacteria sampled from the inner surface of an N95 FFR after donning.