Evaluating the Health Risks of Pneumonia from Airborne Bacterial Communities Using 16S rDNA Sequences of Pneumonia-related Pathogens

Objective Airborne microbial communities include a significant number of uncultured and poorly characterized bacteria.No effective method currently exists to evaluate the health risks of such complex bacterial populations,particularly for pneumonia.Methods We developed a method to evaluate risks from airborne microorganisms,guided by the principle that closer evolutionary relationships reflect similar biological characteristics,and thus used16 S rDNA sequences of 10 common pneumonia-related bacterial pathogens.We calculated a risk of breath-related(Rbr)index of airborne bacterial communities and verified effectiveness with artificial flora and a clinical project.Results We suggested applying Rbr80 to evaluate the health risks of airborne bacterial communities that comprise 80% of dominant operational taxonomic units(OTUs).The feasibility of Rbr80 was confirmed by artificial flora and by pneumonia data from a hospital.A high Rbr80 value indicated a high risk of pneumonia from airborne bacterial communities.Conclusion Rbr80 is an effective index to evaluate the pneumonia-associated risk from airborne bacteria.Values of Rbr80 greater than 15.40 are considered high risk.

Characterization and source analysis of indoor/outdoor culturable airborne bacteria in a municipal wastewater treatment plant

The potential health risks of airborne bacteria emission from a wastewater treatment process have been concerned. However, few studies have investigated the differences in community structure between indoor and outdoor bacteria. In this work, the characterization of airborne bacteria was studied in a municipal wastewater treatment plant in Beijing, China. Two indoor（i.e., fine screen room and sludge dewatering house） and two outdoor（i.e., aeration tank and control site） sampling sites were selected. An Andersen six-stage impactor was used for collecting culturable airborne bacteria in the air, and Illumina MiSeq sequencing was conducted to track the emission source of the culturable airborne bacteria. The results indicate that, compared with the outdoor aeration tank site, the concentrations of culturable airborne bacteria in the indoor fine screen room with poor ventilation were more than ten times higher and the particle size was about twice as large. The community structures of indoor and outdoor culturable airborne bacteria were obviously different. Enterobacteriaceae and opportunistic pathogens were detected in indoor culturable airborne bacteria, with wastewater and sludge dewatering machine identified as the primary sources. Conversely,Enterobacteriaceae and opportunistic pathogens were not detected in outdoor culturable airborne bacteria. Outdoor high wind speed might have resulted in rapid dilution and mixing of culturable airborne bacteria generated from the aeration tank with the ambient air. The results of the present research suggest that covering pollution sources, increasing ventilation rates, and using protective measures for personnel should be implemented to decrease the exposure risk to indoor culturable airborne bacteria.

Characterization of the airborne bacteria community at different distances from the rotating brushes in a wastewater treatment plant by 16S rRNA gene clone libraries

Biological risks of bioaerosols emitted from wastewater treatment processes have attracted wide attention in the recent years. However, the culture-based analysis method has been mostly adopted for detecting the bacterial community in bioaerosols, which may result in the underestimation of total microorganism concentration as not all microorganisms are cultivable. In this study, oligonucleotide fingerprinting of 16S rRNA genes was applied to reveal the composition and structure of the bacterial community in bioaerosols from an Orbal oxidation ditch in a Beijing wastewater treatment plant （WWTP）. Bioaerosols were collected at different distances from the aerosol source, rotating brushes, and the sampling height was 1.5 m which is the common respiratory height of a human being. The bacterial communities of bioaerosols were diverse, and the lowest bacterial diversity was found at the sampling site just after the rotating brush rotating brush. A large proportion of bacteria in bioaerosols were affiliated with Proteobacteria and Bacteroidetes. Numerous bacteria present in the bioaerosols also emerged in water, indicating that the bacterial community in the bioaerosols was related to that of the aerosols＇ sources. The forced aeration of rotating brushes brought about observably distinct bacterial communities between sampling sites situated before and after the rotating brush. Isolation sources of closest relatives in bioaerosols clone libraries were associated with the aqueous environment in the WWTP. Common potential pathogens in bioaerosols as well as those not reported in previous research were also analyzed in this study. Measures should be adopted to reduce the emission of bioaerosols and prevent their exposure to workers.

Airborne bacteria associated with particulate matter from a highly urbanised metropolis:A potential risk to the population’s health

Bacteria in the air present patterns in space and time produced by different sources and environmental factors.Few studies have focused on the link between airborne pathogenic bacteria in densely populated cities,and the risk to the population’s health.Bacteria associated with particulate matter(PM)were monitored from the air of Mexico City(Mexico).We employed a metagenomic approach to characterise bacteria using the 16S rRNA gene.Airborne bacteria sampling was carried out in the north,centre,and south of Mexico City,with different urbanisation rates,during 2017.Bacteria added to the particles were sampled using high-volume PM_(10) samplers.To ascertain significant differences in bacterial diversity between zones and seasons,the Kruskal-Wallis,Wilcoxon tests were done on alpha diversity parameters.Sixty-three air samples were collected,and DNA was sequenced using next-generation sequencing.The results indicated that the bacterial phyla in the north and south of the city were Firmicutes,Cyanobacteria,Proteobacteria,and Actinobacteria,while in the central zone there were more Actinobacteria.There were no differences in the alpha diversity indices between the sampled areas.According to the OTUs,the richness of bacteria was higher in the central zone.Alpha diversity was higher in the rainy season than in the dry season;the Shannon index and the OTUs observed were higher in the central zone in the dry season.Pathogenic bacteria such as Kocuria,Paracoccus,and Micrococcus predominated in both seasonal times,while Staphylococcus,Corynebacterium,and Nocardioides were found during the rainy season,with a presence in the central zone.

The size distribution of airborne bacteria and human pathogenic bacteria in a commercial composting plant

Composting plants are regarded as one of the important sources of environmental bioaerosols.However,limitations in the size distribution of airborne bacteria have prevented our comprehensive understanding of their risk to human health and their dispersal behavior.In this study,different sizes of airborne bacteria were collected using an eight-stage impactor from a full-scale composting facility.Size-related abundance and communities of airborne bacteria as well as human pathogenic bacteria(HPB)were investigated using 16S rRNA gene sequencing coupled with droplet digital PCR.Our results indicate that the bacterial concentrations from the eight stages were approximately 10^(4)-105copies/m^(3).Although no statistical correlation was detected between the particle size and the Shannon index,the influence of size on bacterial lineages was observed in both composting and packaging areas.For airborne bacteria from different stages,the dominant phyla were Firmicutes,Proteobacteria,and Actinobacteria,and the dominant genera was Bacillus.Seven out of eight HPB with a small geometric mean aerodynamic diameter had a high concentration in composting areas.Based on diameters of 2.42 to 5.09μm,most HPB in the composting areas were expected to be deposited on the bronchus and secondary bronchus.However,in the packaging areas,the deposition of HPB(diameters 3.70 to 8.96μm)occurred in the upper part of the respiratory tract.Our results on the size distribution,abundance,and diversity of these bacteria offer important information for the systematic evaluation of bacterial pathogenicity and the potential health impacts on workers in composting plants and the surrounding residents.