Comprehensive performance evaluation of six bioaerosol samplers based on an aerosol wind tunnel

Seasonal dynamics of the phage-bacterium linkage and associated antibiotic resistome in airborne PM2.5 of urban areas

Inhalable microorganisms in airborne fine particulate matter (PM2.5), including bacteria and phages, are major carriers of antibiotic resistance genes (ARGs) with strong ecological linkages and potential health implications for urban populations. A full-spectrum study on ARG carriers and phage-bacterium linkages will shed light on the environmental processes of antibiotic resistance from airborne dissemination to the human lung microbiome. Our metagenomic study reveals the seasonal dynamics of phage communities in PM2.5, their impacts on clinically important ARGs, and potential implications for the human respiratory microbiome in selected cities of China. Gene-sharing network comparisons show that air harbours a distinct phage community connected to human- and water-associated viromes, with 57 % of the predicted hosts being potential bacterial pathogens. The ARGs of common antibiotics, e.g., peptide and tetracycline, dominate both the antibiotic resistome associated with bacteria and phages in PM2.5. Over 60 % of the predicted hosts of vARG-carrying phages are potential bacterial pathogens, and about 67 % of these hosts have not been discovered as direct carriers of the same ARGs. The profiles of ARG-carrying phages are distinct among urban sites, but show a significant enrichment in abundance, diversity, temperate lifestyle, and matches of CRISPR (short for 'clustered regularly interspaced short palindromic repeats') to identified bacterial genomes in winter and spring. Moreover, phages putatively carry 52 % of the total mobile genetic element (MGE)-ARG pairs with a unique 'flu season' pattern in urban areas. This study highlights the role that phages play in the airborne dissemination of ARGs and their delivery of ARGs to specific opportunistic pathogens in human lungs, independent of other pathways of horizontal gene transfer. Natural and anthropogenic stressors, particularly wind speed, UV index, and level of ozone, potentially explained over 80 % of the seasonal dynamics of phage-bacterial pathogen linkages on antibiotic resistance. Therefore, understanding the phage-host linkages in airborne PM2.5, the full-spectrum of antibiotic resistomes, and the potential human pathogens involved, will be of benefit to protect human health in urban areas.

Versatile filter membrane for effective sampling and real-time quantitative detection of airborne pathogens

Construction of air filter membranes bearing prominent collecting and transferring capability is highly desirable for detecting airborne pathogens but remains challenging. Here, a hyaluronic acid air filter membrane (HAFM) with tunable heterogeneous micro-nano porous structures is straightforwardly constructed through the ethanol-induced phase separation strategy. Airborne pathogens can be trapped and collected by HAFM with high performance due to the ideal trade-off between removal efficiency and pressure drop. By exempting the sample elution and extraction processes, the HAFM after filtration sampling can not only directly disperse on the agar plate for colony culture but also turn to an aqueous solution for centrifugal enrichment, which significantly reduces the damage and losses of the captured microorganisms. The following combination with ATP bioluminescence endows the HAFM with a real-time quantitative detection function for the captured airborne pathogens. Benefiting from high-efficiency sampling and non-traumatic transfer of airborne pathogens, the real-world bioaerosol concentration can be facilely evaluated by the HAFM-based ATP assay. This work thus not only provides a feasible strategy to fabricate air filter membranes for efficient microbial collection and enrichment but also sheds light on designing advanced protocols for real-time detection of bioaerosols in the field.

Sampling efficiency and nucleic acid stability during long-term sampling with different bioaerosol samplers

Aerosol microbiome studies have received increased attention as technological advancements have made it possible to dive deeper into the microbial diversity. To enhance biomass collection for metagenomic sequencing, long-term sampling is a common strategy. While the impact of prolonged sampling times on microorganisms' culturability and viability is well-established, its effect on nucleic acid stability remains less understood but is essential to ensure representative sample collection. This study evaluated four air samplers (SKC BioSampler, SASS3100, Coriolis μ, BioSpot-VIVAS 300-P) against a reference sampler (isopore membrane filters) to identify nucleic acid stability during long-term sampling. Physical sampling efficiencies determined with a fluorescent tracer for three particle sizes (0.8, 1, and 3 μm), revealed high efficiencies (> 80% relative to reference) for BioSampler, SASS3100, and BioSpot-VIVAS for all particle sizes, and for Coriolis with 3 μm particles. Coriolis exhibited lower efficiency for 0.8 μm (7%) and 1 μm (50%) particles. During 2-h sampling with MS2 and Pantoea agglomerans, liquid-based collection with Coriolis and BioSampler showed a decrease in nucleic acid yields for all test conditions. BioSpot-VIVAS displayed reduced sampling efficiency for P. agglomerans compared to MS2 and the other air samplers, while filter-based collection with SASS3100 and isopore membrane filters, showed indications of DNA degradation for 1 μm particles of P. agglomerans after long-term sampling. These findings show that long-term air sampling affects nucleic acid stability in both liquid- and filter-based collection methods. These results highlight bias produced by bioaerosol collection and should be considered when selecting an air sampler and interpreting aerosol microbiome data.

On-Site Bioaerosol Sampling and Airborne Microorganism Detection Technologies

Bioaerosols are small airborne particles composed of microbiological fragments, including bacteria, viruses, fungi, pollens, and/or by-products of cells, which may be viable or non-viable wherever applicable. Exposure to these agents can cause a variety of health issues, such as allergic and infectious diseases, neurological disorders, and cancer. Therefore, detecting and identifying bioaerosols is crucial, and bioaerosol sampling is a key step in any bioaerosol investigation. This review provides an overview of the current bioaerosol sampling methods, both passive and active, as well as their applications and limitations for rapid on-site monitoring. The challenges and trends for detecting airborne microorganisms using molecular and immunological methods are also discussed, along with a summary and outlook for the development of prompt monitoring technologies.