Airborne Bacterial Communities Research Articles

Bioaerosol Sampling Devices and Pretreatment for Bacterial Characterization: Theoretical Differences and a Field Experience in a Wastewater Treatment Plant.

Studies on bioaerosol bacterial biodiversity have relevance in both ecological and health contexts, and molecular methods, such as 16S rRNA gene-based barcoded sequencing, provide efficient tools for the analysis of airborne bacterial communities. Standardized methods for sampling and analysis of bioaerosol DNA are lacking, thus hampering the comparison of results from studies implementing different devices and procedures. Three samplers that use gelatin filtration, swirling aerosol collection, and condensation growth tubes for collecting bioaerosol at an aeration tank of a wastewater treatment plant in Trieste (Italy) were used to determine the bacterial biodiversity. Wastewater samples were collected directly from the untreated sewage to obtain a true representation of the microbiological community present in the plant. Different samplers and collection media provide an indication of the different grades of biodiversity, with condensation growth tubes and DNA/RNA shieldTM capturing the richer bacterial genera. Overall, in terms of relative abundance, the air samples have a lower number of bacterial genera (64 OTUs) than the wastewater ones (75 OTUs). Using the metabarcoding approach to aerosol samples, we provide the first preliminary step toward the understanding of a significant diversity between different air sampling systems, enabling the scientific community to orient research towards the most informative sampling strategy.

Environmental factors and particle size shape the community structure of airborne total and pathogenic bacteria in a university campus.

Given the dense population on university campuses, indoor and outdoor airborne bacterial contamination may lead to the rapid spread of diseases in a university environment. However, there are few studies of the characteristics of airborne and pathogenic bacterial communities in different sites on a university campus. In this study, we collected particulate matter samples from indoor and outdoor locations at a university in Bengbu City, Anhui Province, China, and analyzed the community characteristics of airborne and pathogenic bacteria using a high-throughput sequencing technique. The results showed that the composition of the dominant airborne and pathogenic bacterial communities was consistent among sites at the phylum and genus levels, with differences in their relative abundance. There were significant differences in the structure of the airborne and pathogenic bacterial communities between indoor and outdoor sites (p < 0.05). An analysis of similarities (ANOSIM) indicated that the structure of airborne bacterial communities in indoor sites was influenced by the room occupancy rate, ventilation conditions, and the extent of indoor furnishing (p < 0.05), while the structure of pathogenic bacterial communities was influenced by the number of individuals and spatial dimensions (p < 0.05). The impact of particle size on the structure of airborne and pathogenic bacterial communities was relatively minor. A total of 194 suspected pathogenic bacterial species were identified, accounting for 0.0001-1.3923% of the total airborne bacteria, all of which were conditional pathogens. Among them, Saccharopolyspora rectivirgula, Acinetobacter johnsonii, and Moraxella osloensis exhibited relatively high relative abundance, accounting for 24.40, 16.22, and 8.66% of the total pathogenic bacteria, respectively. Moreover, 18 emerging or re-emerging pathogenic bacterial species with significant implications for human health were identified, although their relative abundance was relatively low (0.5098%). The relative abundance of pathogenic bacteria in indoor environments was significantly higher than outdoors, with the laboratory and dormitory having the highest levels. The findings of this study provide valuable guidance for the prevention and control of airborne bacterial contamination and the associated health risks in both a campus environment and other public spaces with high occupancy rates.

Fungal community shows more variations by season and particle size than bacteria

The global concern regarding the health risk associated with airborne microorganisms has prompted research in this field. However, there is a lack of systematic investigation into the particle-size distribution of airborne bacterial and fungal communities associated with seasons, which determines where they are deposited in the human respiratory tract. To address this gap, we conducted a study in Nanchang, located in central China, where we collected both coarse and fine particles during summer and winter seasons. The results demonstrated that microbial community exhibited obvious seasonal and particle-size variations except bacterial community in fine particles. Certain taxa (e.g., Bacteroidales, Ktedonobacterales, Capnodiales) displayed either seasonal and/or particle-size preferences. Furthermore, airborne microorganisms in coarse particles were more sensitive to season and particle size compared to those in fine particles, with fungal community being more susceptible than bacterial community. The susceptibility can be attributed to their high vulnerability to air pollutants and meteorological conditions, primarily PM2.5 and PM10. Additionally, a greater relative abundance of pathogenic fungi was observed in fine particles, even though microbial diversity in coarse particles was noticeably higher than that in fine particles. Furthermore, some predominant pathogens such as Alternaria, Nigrospora, and Escherichia-Shigella not only had particle size and/or seasonal preferences, but also were strongly correlated with environmental factors. This study advances our understanding of atmospheric pathogenic microorganisms and highlights the fungal health threat.

Human Exposure to Ambient Atmospheric Microplastics in a Megacity: Spatiotemporal Variation and Associated Microorganism-Related Health Risk.

Microplastics are found in various human tissues and are considered harmful, raising concerns about human exposure to microplastics in the environment. Existing research has analyzed indoor and occupational scenarios, but long-term monitoring of ambient atmospheric microplastics (AMPs), especially in highly polluted urban regions, needs to be further investigated. This study estimated human environmental exposure to AMPs by considering inhalation, dust ingestion, and dermal exposure in three urban functional zones within a megacity. The annual exposure quantity was 7.37 × 104 items for children and 1.06 × 105 items for adults, comparable with the human microplastic consumption from food and water. Significant spatiotemporal differences were observed in the characteristics of AMPs that humans were exposed to, with wind speed and rainfall frequency mainly driving these changes. The annual human AMP exposure quantity in urban green land spaces, which were recognized as relatively low polluted zones, was comparable with that in public service zones and residential zones. Notably, significant positive correlations between the AMP characteristics and the pathogenicity of the airborne bacterial community were discovered. AMP size and immune-mediated disease risks brought by atmospheric microbes showed the most significant relationship, where Sphingomonas might act as the potential key mediator.

Fog caused distinct diversity of airborne bacterial communities enriched with pathogens over central Indo-Gangetic plain in India

Fog causes enhancement of bacterial loading in the atmosphere. Current study represents the impact of occurrences of fog on the alteration of diversity of airborne bacteria and their network computed from metagenomic data of airborne samples collected at Arthauli (25.95°N, 85.10°E) situated at central Indo-Gangetic Plain (IGP) during 1–14 January 2021. A distinct bacterial diversity with a complex network is identified in foggy condition due to the enrichment of unique types of bacteria. Present investigation highlights a statistically significant enrichment of airborne pathogenic bacteria found in a unique ecosystem within air evolved due to the occurrences of fog over central IGP. In the foggy network, Cutibacterium, an opportunistic pathogen, is identified to be interacting maximum (21 edges) with other bacteria with statistically significant copresence relation, which are responsible for various infections for human beings. A 40–60% increase (p < 0.01) in the abundance of pathogenic bacteria for respiratory and skin diseases is noticed in fog period. Among the fog-enriched bacteria, Cutibacterium, Herbaspirillum, Paenibacillus, and Tsukamurella are examples of opportunistic bacteria causing various respiratory diseases, while Paenibacillus can even cause skin cancer and acute lymphoblastic leukemia.

Studies on the airborne bacterial communities and antimicrobial resistance genes in duck houses based on metagenome and PCR analysis

The threat of antimicrobial resistance (AMR) is on the rise globally, especially with the development of animal husbandry and the increased demand for antibiotics. Livestock and poultry farms, as key sites for prevalence of antibiotic-resistant bacteria (ARB), can spread antimicrobial resistance genes (ARGs) through microbial aerosols and affect public health. In this study, total suspended particulate matter (TSP) and airborne culturable microorganisms were collected from duck houses in Tai'an, Shandong Province, and the bacterial communities and airborne ARGs were analyzed using metagenomics and PCR methods. The results showed that the bacterial communities in the air of duck houses were mainly Actinobacteria, Firmicutes, Proteobactria, Chlamydia, and Bcateroidetes at the phylum level. At the genus level, the air was dominated by Corynebacterium, Jeotgalicoccus, Staphylococcus, Brevibacterium, and Megacoccus, and contained some pathogenic bacteria such as Staphylococcus aureus, Corynebacterium diphtheriae, Klebsiella oxytoca, Acinetobacter baumannii, and Pseudomonas aeruginosa, which were also potential hosts for ARGs. The airborne ARGs were mainly macrolides (10.97%), penicillins (10.73%), cephalosporins (8.91%), streptozotocin (8.91%), and aminoglycosides (8.02%). PCR detected 27 ARGs in airborne culturable microorganisms, and comparative analysis between PCR and the metagenomic data revealed that a total of 9 ARGs were found to the same, including macrolides ErmA, ErmF, tetracyclines tetG, tetX, methicarbamazepines dfrA12, dfrA15, aminoglycosides APH3-VI, ANT2-Ⅰ, and sulfonamides sul2. Moreover, inhalation exposure modeling showed that the workers in duck houses inhaled higher concentrations of ARB, human pathogenic bacteria (HPB) and human pathogenic antibiotic-resistant bacteria (HPARB) than hospital workers. These results provide new insights into airborne microorganisms and ARGs in animal farms and lay the foundation for further study.

Airborne bacterial communities associated with particulate matter in Temuco (Chile), one of the most air-polluted cities in South America

Airborne bacterial communities associated with particulate matter in Temuco (Chile), one of the most air-polluted cities in South America

Seasonal variations of airborne microbial diversity in waste transfer stations and preventive effect on Streptococcus pneumoniae induced pulmonary inflammation

Environment, location, and season are important factors that influence the microbiological community, yet, little research on airborne microorganisms in waste transfer stations (WTSs). Here, the airborne bacterial and fungal communities at four WTSs during different seasons were analyzed by high-throughput sequencing. The bacteria were isolated by cultural method and screened bacterium alleviate inflammation induced by Streptococcus pneumoniae (Spn) by regulating gut microbiome. The results revealed that collected bioaerosols from the WTSs varied significantly by location and season. Proteobacteria and Pseudomonadota are prevalent in summer and winter, respectively. Ascomycota was predominant in two seasons. Hazard quotients for adults from four WTSs were below one. Three selected potential probiotics were formulated into a microbial preparation with a carrier that effectively prevented inflammation in bacterial and animal experiments. The expression levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in Pre group (0.11, 0.17, and 0.48-fold) were significantly lower than Spn group (2.75, 1.71, and 5.01-fold). These mechanisms are associated with changes in gut microbiota composition and short-chain fatty acids (SCFAs) levels, such as affecting Lachnospiraceae lachnospira abundance and acetic acid content. This study provides insights into the potential application of probiotics derived from WTSs as an alternative approach to preventing respiratory infections.

Characterization of the Airborne Microbiome in Different Indoor and Outdoor Locations of a University Building Using an Innovative Compositional Data Analysis Approach

In this work, we investigated the structure of the airborne bacterial community obtained by 16S rRNA gene sequencing performed on aerosol samples from different indoor and outdoor locations. The 48-h aerosol samples were collected in two laboratories, in the corridors, and on the roof of the Mathematics and Physics Department of the University of Salento (Italy). The investigation was carried out through the application of an innovative compositional data analysis approach, mainly based on a centered log-ratio transformation as a standardization procedure, the Aitchison distance for data ordination, and the principal component analysis via singular value decomposition for data clustering. This methodology allowed us to explore the main relationships among samples, identifying different results between indoor and outdoor samples both at the genus level and at the species level. Bacillus and Pseudomonas represented the most abundant genera identified in the analyzed samples. Out of the 21 identified bacterial species with the highest abundances in the collected aerosol samples, Acinetobacter lwoffii, Propionibacterium acnes, Diplorickettsia massiliensis, and Corynebacterium tuberculostearicum were the only four commonly classified as human opportunistic pathogens. Among the genera mostly associated with indoor environments, Hymenobacter and Arthrobacter could be noted as including many species that are unique in being radiation resistant.

Childhood lower respiratory tract infections linked to residential airborne bacterial and fungal microbiota

Residential microbial composition likely contributes to the development of lower respiratory tract infections (LRTI) among children, but the association is poorly understood. We aimed to study the relationship between the indoor airborne dust bacterial and fungal microbiota and childhood LRTI in Ibadan, Nigeria.Ninety-eight children under the age of five years hospitalized with LRTI were recruited and matched by age (±3 months), sex, and geographical location to 99 community-based controls without LRTI. Participants’ homes were visited and sampled over a 14-day period for airborne house dust using electrostatic dustfall collectors (EDC). In airborne dust samples, the composition of bacterial and fungal communities was characterized by a meta-barcoding approach using amplicons targeting simultaneously the bacterial 16S rRNA gene and the internal-transcribed-spacer (ITS) region-1 of fungi in association with the SILVA and UNITE database respectively.A 100-unit change in house dust bacterial, but not fungal, richness (OR 1.06; 95%CI 1.03–1.10) and a 1-unit change in Shannon diversity (OR 1.92; 95%CI 1.28–3.01) were both independently associated with childhood LRTI after adjusting for other indoor environmental risk factors. Beta-diversity analysis showed that bacterial (PERMANOVA p < 0.001, R2 = 0.036) and fungal (PERMANOVA p < 0.001, R2 = 0.028) community composition differed significantly between homes of cases and controls. Pair-wise differential abundance analysis using both DESEq2 and MaAsLin2 consistently identified the bacterial phyla Deinococcota (Benjamini-Hochberg (BH) adjusted p-value <0.001) and Bacteriodota (BH-adjusted p-value = 0.004) to be negatively associated with LRTI. Within the fungal microbiota, phylum Ascomycota abundance (BH adjusted p-value <0.001) was observed to be directly associated with LRTI, while Basidiomycota abundance (BH adjusted p-value <0.001) was negatively associated with LRTI.Our study suggests that early-life exposure to certain airborne bacterial and fungal communities is associated with LRTI among children under the age of five years.

Spatial distribution of airborne bacterial communities in caged poultry houses

ABSTRACT Microbial aerosols in intensive broiler houses whose species and concentrations are closely related to human health are ubiquitous. Based on 16S rRNA gene sequencing, the aim of this study was to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. Significant spatial variations in airborne bacterial concentrations were observed inside the poultry farmhouse. The results indicated that bacteria in the air samples could be grouped into a total of 1,674 OTUs. Alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (p < 0.01). The Sankey diagram illustrated species dynamic changes in Proteobacteria, Firmicutes, and Actinobacteria among the different locations. From the aspect of LEfSe (LDA Effect Size) analysis, we discovered that the abundance of Planctomycetes was significantly higher in the entry than in the rear and middle. This study shows the spatial distribution of the entire bacterial community in intensive broiler houses, which offers a new perspective for studying airborne total bacteria in those environments. Implications: The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the spatial distribution and diversity of bacterial aerosols in the air of broiler houses. The results observed that bacterial aerosol concentrations in the examined broilers house varied greatly at different positions, and a significantly higher exposure to bacterial aerosol was observed at the middle than at the other positions (p < 0.05). The alpha diversity analysis showed that the diversity of the microbial community at the entry of the broiler house was higher than that at the middle or the rear (P<0.01). Sankey diagram illustrated species dynamic changes of Proteobacteria, Firmicutes and Actinobacteria among the different locations. The microbial communities in genus level in the samples of entry and rear were closer, while the species diversity of middle and rear samples in chicken house was highly similar (P>0.05). Altogether, results revealed that the effects of spatial factors on the diversity and abundance of bacteria in the air of closed-cage broiler houses, which poses a potential threat to the health of animals and workers in those environments.

Aerial transport of bacteria by dust plumes in the Eastern Mediterranean revealed by complementary rRNA/rRNA-gene sequencing

Processes influencing the transport of airborne bacterial communities in the atmosphere are poorly understood. Here, we report comprehensive and quantitative evidence of the key factors influencing the transport of airborne bacterial communities by dust plumes in the Eastern Mediterranean. We extracted DNA and RNA from size-resolved aerosols sampled from air masses of different origins, followed by qPCR and high-throughput amplicon sequencing of 16 S ribosomal RNA gene and transcripts. We find that airborne bacterial community composition varied with air mass origin and particle size. Bacterial abundance, alpha diversity and species richness were higher in terrestrially influenced air masses than in marine-influenced air masses and higher in the coarse particle fraction (3.0 to 10.0 µm) than in the fine fraction (0.49 to 1.5 µm). This suggests that airborne bacteria mainly were associated with dust particles or transported as cell aggregates. High abundances of rRNA from human, animal and plant pathogen taxa indicate potential ecological impacts of atmospheric bacterial transport.

Airborne bacterial community and antibiotic resistome in the swine farming environment: Metagenomic insights into livestock relevance, pathogen hosts and public risks

Globally extensive use of antibiotics has accelerated antimicrobial resistance (AMR) in the environment. As one of the biggest antibiotic consumers, livestock farms are hotspots in AMR prevalence, especially those in the atmosphere can transmit over long distances and pose inhalation risks to the public. Here, we collected total suspended particulates in swine farms and ambient air of an intensive swine farming area. Bacterial communities and antibiotic resistomes were analyzed using amplicon and metagenomic sequencing approaches. AMR risks and inhalation exposure to potential human-pathogenic antibiotic-resistant bacteria (HPARB) were subsequently estimated with comparison to the reported hospital samples. The results show that swine farms shaped the airborne bacterial community by increasing abundances, reducing diversities and shifting compositions. Swine feces contributed 77% of bacteria to swine farm air, and about 35% to ambient air. Airborne antibiotic resistomes in swine farms mainly conferred resistance to tetracyclines, aminoglycosides and lincosamides, and over 48% were originated from swine feces. Distinct to the hospital air, Firmicutes were dominant bacteria in swine farming environments with conditional pathogens including Clostridium, Streptococcus and Aerococcus being major hosts of antibiotic resistance genes (ARGs). Therein, genomes of S. alactolyticus carrying (transposase/recombinase-associated) ARGs and virulence factor genes were retrieved from the metagenomes of all swine feces and swine farm air samples, but they were not detected in any hospital air samples. This suggests the indication of S. alactolyticus in swine farming environments with potential hazards to human health. Swine farm air faced higher AMR risks than hospital air and swine feces. The inhalation intake of HPARB by a swine farm worker was about three orders of magnitude higher than a person who works in the hospital. Consequently, this study depicted atmospheric transmission of bacteria and antibiotic resistomes from swine feces to the environment.

Optimization of bacterial DNA and endotoxin extraction from settled airborne dust.

Collecting and obtaining sufficient amount of airborne particles for multiple microbial component assessments can be challenging. A passive dust sampling device, the electrostatic dust fall collector (EDC) has been established for assessing airborne exposures including endotoxin and glucans. Recently, with advances in next-generation sequencing techniques, EDCs were used to collect microbial cells for DNA sequencing analysis to promote the study of airborne bacterial and fungal communities. However, low DNA yields have been problematic when employing passive sampling with EDC. To address this challenge, we attempted to increase the efficiency of extraction. We compared DNA extraction efficiency of bacterial components from EDCs captured on filters through filtration using five extraction techniques. By measuring the abundance, diversity and structure of bacterial communities using qPCR and amplicon sequencing targeting 16S rRNA genes, we found that two techniques outperformed the rest. Furthermore, we developed protocols to simultaneously extract both DNA and endotoxin from a single EDC cloth. Our technique promotes a high quality to price ratio and may be employed in large epidemiological studies addressing airborne bacterial exposure where a large number of samples is needed.

Bacterial Community Characteristics Shaped by Artificial Environmental PM2.5 Control in Intensive Broiler Houses.

Multilayer cage-houses for broiler rearing have been widely used in intensive Chinese farming in the last decade. This study investigated the characteristics and influencing factors of bacterial communities in the PM2.5 of broiler cage-houses. The PM2.5 samples and environmental variables were collected inside and outside of three parallel broiler houses at the early, middle, and late rearing stages; broiler manure was also gathered simultaneously. The bacterial 16S rRNA sequencing results indicated that indoor bacterial communities were different from the outdoor atmosphere and manure. Furthermore, the variations in airborne bacterial composition and structure were highly influenced by the environmental control variables at different growth stages. The db-RDA results showed that temperature and wind speed, which were artificially modified according to managing the needs for broiler growth, were the main factors affecting the diversity of dominant taxa. Indoor airborne and manurial samples shared numerous common genera, which contained high abundances of manure-origin bacteria. Additionally, the airborne bacterial community tended to stabilize in the middle and late stages, but the population of potentially pathogenic bacteria grew gradually. Overall, this study enhances the understanding of airborne bacteria variations and highlighted the potential role of environmental control measures in intensive farming.

Distribution characteristics of airborne bacterial community in different anthropogenic activity regions across Nanchang, China

Bacteria are widely dispersed in the atmosphere by attaching on the particulate matters (PM), which have profound implications for public health and global climate. The association between anthropogenic activity and airborne bacteria remains unclear. To reveal it, the bacterial diversity and community structures of PM2.5 collected from five different anthropogenic activity regions in Nanchang, China, were compared. We found that bacteria in UPM and SPM with relatively intensive anthropogenic activities had higher richness and diversity than the other three regions, which was confirmed by the strongly positive correlations between richness/diversity indices and PM10/NO2 concentrations. Moreover, the phyla Actinobacteria and Deinococcus-Thermus were enriched in UPM and SPM, and several soil-sourced genera such as Deinococcus, Rumbellimicrobium, and Blastococcus, were also dominant in UPM and SPM. Mantel test and correlation analysis showed that human-related air pollutants were one main reason for the disparities of airborne bacterial community (r = 0.26, p < 0.01). And the above taxa in UPM and SPM showed significantly correlation with air pollutants, while several dominant taxa such as Cyanobacteria in TPM and Chloroflexi in FPM had no obvious relationship. The results suggested that the disturbance of intensively anthropogenic activities facilitated some soil derived bacteria to enter into the air. Notably, part of them such as Kocuria, Arthrobacter, and Paracoccus, were human opportunistic pathogens. This work further our understanding of anthropogenic activity impacts on airborne bacteria, especially human pathogens.

Global airborne bacterial community—interactions with Earth’s microbiomes and anthropogenic activities

Airborne bacteria are an influential component of the Earth's microbiomes, but their community structure and biogeographic distribution patterns have yet to be understood. We analyzed the bacterial communities of 370 air particulate samples collected from 63 sites around the world and constructed an airborne bacterial reference catalog with more than 27 million nonredundant 16S ribosomal RNA (rRNA) gene sequences. We present their biogeographic pattern and decipher the interlacing of the microbiome co-occurrence network with surface environments of the Earth. While the total abundance of global airborne bacteria in the troposphere (1.72 × 1024 cells) is 1 to 3 orders of magnitude lower than that of other habitats, the number of bacterial taxa (i.e., richness) in the atmosphere (4.71 × 108 to 3.08 × 109) is comparable to that in the hydrosphere, and its maximum occurs in midlatitude regions, as is also observed in other ecosystems. The airborne bacterial community harbors a unique set of dominant taxa (24 species); however, its structure appears to be more easily perturbed, due to the more prominent role of stochastic processes in shaping community assembly. This is corroborated by the major contribution of surface microbiomes to airborne bacteria (averaging 46.3%), while atmospheric conditions such as meteorological factors and air quality also play a role. Particularly in urban areas, human impacts weaken the relative importance of plant sources of airborne bacteria and elevate the occurrence of potential pathogens from anthropogenic sources. These findings serve as a key reference for predicting planetary microbiome responses and the health impacts of inhalable microbiomes with future changes in the environment.

Size distribution, community composition, and influencing factors of bioaerosols on haze and non-haze days in a megacity in Northwest China.

Bioaerosols have become a major environmental concern in recent years. In this study, the diurnal variations and size distributions of bioaerosols, as well as airborne bacterial community compositions and their influencing factors on haze and non-haze days in Xi'an, China, were compared. The results indicated that the mean bacteria and fungi concentrations on non-haze days were 1.7 and 1.4 times of those on haze days, respectively, whereas the mean total airborne microbe (TAM) concentration was higher on haze days. Bacteria concentrations were the lowest in the afternoon, and the TAM concentration exhibited a bimodal distribution with two peaks coinciding with traffic rush hours. On haze days airborne fungi was mainly attached to PM2.5, whereas bacteria and TAM were mainly distributed in coarse PM. The relative abundance of Chao1, Shannon and Simpson indices of bacterial communities were higher in the non-haze day samples, for the reason that high PM2.5 levels with a large specific surface area may absorb more toxic and harmful substances on haze days, which should affect microbial growth. At the generic level, the relative abundance of Rhodococcus, Paracoccus, Acinetobacter, and Kocuria on haze days was higher than that on non-haze days, indicating a higher risk of contracting pathogenic pneumonia. The results of the redundancy analysis revealed that PM2.5 and water-soluble inorganic ions (WSIIs, NO3-, SO42+, and NH4+) strongly affected the bacterial communities on non-haze days, especially Acinetobacter. The atmospheric oxidation capacity (Ox) had a significant effect on bacterial communities during haze episodes, which were positively correlated with Paracoccus, Deinococcus, Sphingomonas, and Rubellimicrobium and were negatively correlated with Rhodococcus. These results provide valuable data to elucidate the formation and evolution of bioaerosol between haze and non-haze events and its potential threats to human health.

Simultaneous monitoring of SARS-CoV-2 and bacterial profiles from the air of hospital environments with COVID-19-affected patients

The SARS-CoV-2 presence and the bacterial community profile in air samples collected at the Intensive Care Unit (ICU) of the Operational Unit of Infectious Diseases of Santa Caterina Novella Hospital in Galatina (Lecce, Italy) have been evaluated in this study. Air samplings were performed in different rooms of the ICU ward with and without COVID-19 patients. No sample was found positive to SARS-CoV-2, according to Allplex 2019-nCoV Assay. The airborne bacterial community profiles determined by the 16S rRNA gene metabarcoding approach up to the species level were characterized by richness and biodiversity indices, Spearman correlation coefficients, and Principal Coordinate Analysis. Pathogenic and non-pathogenic bacterial species, also detected in outdoor air samples, were found in all collected indoor samples. Staphylococcus pettenkoferi, Corynebacterium tuberculostearicum, and others coagulase-negative staphylococci, detected at high relative abundances in all the patients’ rooms, were the most abundant pathogenic species. The highest mean relative abundance of S. pettenkoferi and C. tuberculostearicum suggested that they were likely the main pathogens of COVID-19 patients at the ICU ward of this study. The identification of nosocomial pathogens representing potential patients’ risks in ICU COVID-19 rooms and the still controversial airborne transmission of the SARS-CoV-2 are the main contributions of this study.

Airborne bacterial communities in the poultry farm and their relevance with environmental factors and antibiotic resistance genes

The accelerating occurrence and environmental dissemination of bacteria, gas pollutants and antibiotic resistance genes (ARGs) in aerosols of poultry farms have become emerging environmental issues due to their potential threat to animals, workers, and the communities located near such farms. Here, aerosol samples were gathered from inside and outside of the chicken house in winter with a transportable high-flow bioaerosol sampler. Then, 16S rRNA gene amplicon sequencing was used to categorize the bacteria in air samples, and the abundance of 12 ARG subtypes was researched via the real-time quantitative polymerase chain reaction (qPCR). Results indicated that the bacterial richness and diversity and total absolute abundance of ARGs were similar in the bioaerosols from indoor and downwind site of the poultry farm. The zoonotic pathogens, Staphylococcus and Corynebacterium, were detected both inside and outside of the chicken house, and the four most abundant target genes were blaTEM, tetQ, ermB and sul1 in aerosols. Moreover, the correlation between the bacterial communities and environmental factors, such as NH3 and H2S concentrations, wind speed, temperature and relative humidity, was analyzed. The result revealed that the indoor bacteria community was positively associated with temperature and concentrations of air pollutants (NH3 and H2S), and could spread from confinement buildings to the ambient atmosphere through wind. In addition, the network analysis result showed that the airborne bacteria might significantly contribute in shaping the ARGs' profiles in bioaerosol from inside and outside of the poultry house. Overall, our results revealed the airborne bacterial communities and their associated influencing factors in the micro-environment (inside of the chicken house and nearby the boundary of the farm), and brought a new perspective for studying the gas pollutants and bioaerosol from poultry farms in winter.