Airborne Microbes Research Articles

Analysis of the Effectiveness of Masks at Blocking Bacterial Particulates.

In light of the recent pandemic, this study was conducted to determine the effectiveness of masks stopping bacterial particles. The Centers for Disease Control and Prevention (CDC) has recommended a multitude of varying face masks that are said to protect you and others from the spread of COVID-19 and other air-borne microbes. The main goal of this research was to test recommended masks and determine if they are as protective as everyone acknowledges them to be.
 To evaluate the masks, multiple mathematical formulas were used to accurately imitate the average human cough. These calculations were used to build a machine that would expel air and a microbial solution through a mask. A bacterial sample was used to determine the effectiveness of microbe containment by the various masks due to the ability to obtain penetration measurements without the need of host cell infection. The machine constructed to mimic a human cough consists of a pressure regulator, “cough chamber”, and a mouth nozzle. The concentration of bacterial solution was factored into the amount of particulate that is expelled after an average cough. The standardized bacteria-containing cough solution was then dispersed through the mouth nozzle and a mask. Any particulate that passed through the mask was collected on a nutrient agar plate, which was used to quantify the number of microbial particles that breached the mask.
 Preliminary data indicates that there is a difference in the effectiveness of the masks and some masks do not appear to be as effective as they are advertised to be. This calls into question the validity of the CDC’s recommendations for masks effective at preventing the transmission of air-borne microbes.

Mechanism for Reducing the Horizontal Transfer Risk of the Airborne Antibiotic-Resistant Genes of Escherichia coli Species through Microwave or UV Irradiation.

Antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs) as new types of contaminants are discharged into the environment, increasing the risk of horizontal gene transfer (HGT). However, few researchers have examined the impacts of airborne ARB deactivation on HGT risk. The deactivation of airborne Escherichia coli 10667 (carrying sul genes) and the emission and removal of ARGs were mainly investigated in this study. Moreover, the potential mechanisms of HGT and transfer frequencies under microwave (MW) and ultraviolet (UV) irradiation were investigated using the nonresistant E. coli GMCC 13373 and E. coli DH5α with plasmid RP4 as the recipient and donor, respectively. E. coli CICC 10667 and E. coli DH5α with RP4 plasmid achieve log inactivation values as high as 5.5-log and 5.0-log, respectively, which were quite different from the antibiotic-sensitive strain E. coli CGMCC 13373 (3.4-log) subjected to MW irradiation. For UV disinfection, E. coli DH5α with the RP4 plasmid was reduced at 4.4-log, E. coli CGMCC 13373 was reduced at 2.3-log, and E. coli CICC 10667 was inactivated at 2.1-log. The removal rates of ARGs and HGT frequencies under MW irradiation were compared with those under UV irradiation. The ARGs removal efficiency (85.5%) obtained by MW was higher than that obtained by UV (48.2%). Consequently, the HGT frequency (0.008) of airborne ARGs released to the recipient (forward transfer) decreased and was lower than that under UV irradiation (0.014). Moreover, the plasmid RP4 was transferred from the donor to the surviving damaged E. coli 10667 as cell permeability (reverse transfer) was increased at a high HGT frequency (0.003) by MW, which was close to the value by UV (0.002). Additionally, sul1 and sul2 genes were confirmed to be more resistant to MW than the sul3 gene. These findings reveal the mechanism of HGT between damaged E. coli 10667 and surrounding environmental microbes. Microwave is a promising technology for disinfecting airborne microbes and preventing the spread of antibiotic resistance.

Virucidal, bactericidal, and sporicidal multilevel antimicrobial HEPA-ClO2 filter for air disinfection in a palliative care facility

• HEPA-ClO 2 with contact-killing and release-killing properties against microbes. • HEPA-ClO 2 with effective in filtering and killing viruses, bacteria, and spores. • HEPA-ClO 2 is safe according to in-vitro and in-vivo studies. • HEPA-ClO 2 is more efficient than unmodified HEPA in field trial and CFD studies. Pathogenic microbes in the air are the leading cause of respiratory diseases and illnesses, and respiratory viruses are responsible for some of the world’s most devastating epidemics and pandemics. Therefore, their capture, removal, and disinfection are essential in preventing the spread of diseases. A multilevel antimicrobial HEPA-ClO 2 prepared by coating micro-encapsulated chlorine dioxide on high-efficiency particulate air (HEPA-H13) filter, displays broad-spectrum virucidal and bactericidal, as well as sporicidal activities through the combined “contact-killing” and “release-killing” properties. In-vitro cytotoxicity (i.e., human A549 cells) and in-vivo inhalation toxicity tests (i.e., Kunming mice) indicate HEPA-ClO 2 has low inhalation toxicity and is safe. Furthermore, it has superb performance against a panel of infectious respiratory viruses (e.g., influenza viruses, EV-71) and bacteria (e.g., L. pneumophila , K. pneumonia ) and drug-resistant organisms (e.g., MRSA, MRPA), attaining log 2 reduction (99%) within a minute. However, spores required 30 min to reach 99% inactivation. A 260-day field trial study at a palliative care facility demonstrated that air purifiers could significantly decrease airborne particulates and microbes (bacteria and mold/fungi) and confirmed the long-term efficacy of the HEPA-ClO 2 filters and their superiority over uncoated HEPA-H13 against microbes. The experimental results from the wardroom were validated by a computational fluid dynamics (CFD) simulation.

The Effectiveness of The Disinfection Tools of Ultraviolet Radiation Method in Reducing Number of Airborne Microbial in Several Indoors in Hospitals and Offices in Jakarta

The Effectiveness of The Disinfection Tools of Ultraviolet Radiation Method in Reducing Number of Airborne Microbial in Several Indoors in Hospitals and Offices in Jakarta

Microbiological indoor air quality of hospital buildings with different ventilation systems, cleaning frequencies and occupancy levels

Pathogenic airborne microbes are the potential source of infectious diseases transmission. This study aimed to investigate and compare the microbial load, composition and prevalence of fungal and bacterial species at hospital sites facilitated with different ventilation systems and having different disinfection frequencies and occupancy levels. For this purpose, sixteen sampling sites were selected in two public hospital buildings including outpatient departments (OPDs), surgical wards, operation theaters (OTs), emergency departments, waiting room, burn unit, intensive care unit, nursing unit and medical laboratory. Results showed highest bacterial (829–4980 CFU/m3) and fungal levels (90–920 CFU/m3) in OPDs and wards respectively, whereas lowest concentration was observed in OTs of both hospitals. Overall, sites facilitated with central/mechanical heating ventilation and air conditioning (HVAC) system, higher cleaning frequency and lower occupant's density showed lower contamination levels. Staphylococcus spp. (53%), Micrococcus spp. (30%) and Bacillus spp. (11%) were found as abundantly occurring bacterial microbiota whereas Aspergillus spp. (67%) and Penicillium spp. (28%) were predominant fungal genera observed.

Novel air sterilization process for clean air production and microbial spread limitation using protection devices.

This work aims to develop and simulate a novel process based on sterilizing natural air by heating at high temperatures followed by rapid cooling. The new sustainable process is called “Air Rapid Heating Rapid Cooling Sterilization” (ARHRCS). Thus, it can be used in Heating, Ventilation, and Air Conditioning (HVAC) systems in hospitals to produce safe air, free of pathogenic airborne microbes including bacteria and viruses such as tuberculosis (TB) and coronavirus (SARS-CoV-2). A crown fixed on the head of the medical staff may be connected to the HVAC system to produce a constant flow of clean laminar air. Hence, this crown is capable of keeping airborne microorganisms at a safe distance from Health Care Workers (HCWs), avoiding any potential microbial infection. Accordingly, HCWs will be able to work in more suitable and safe conditions, especially in high infection risk areas. Depending on its need, the newly developed process may be implemented in different other locations such as laboratories, malls, planes, buildings, and other crowded spaces. Further applications of this method may arise including its usage in the sterilization of recirculated air in biosafety cabinets and the development of a portable air sterilizing unit.

Relationships between airborne microbial community diversity, heating supply patterns and particulate matter properties

Airborne microbes play critical roles in atmospheric ecology and human health, while the connections of microbial community with anthropic activity, such as heating supply patterns and chemical compositions of particulate matter (PM), remain unclear. The present study demonstrated that district heating supply regions exhibited higher microbial richness than non-district heating supply regions, and microbial richness in PM1 (aerodynamic diameter ≤ 1 µm) was significantly lower than that in PM10 (aerodynamic diameter ≤ 10 µm). Gram-positive bacteria were dominant, and Bacilli accounts for 85% of the noted bacteria. The total concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs) and water-soluble ions increased with PM sizes. Heavy metals and PAHs in non-district heating supply regions showed significantly higher concentrations than that in district heating supply regions. Most of tested chemical compositions negatively contributed to microbial community diversity, except for Zn, Cr, Pyrene (Pyr), and Benzo[a]pyrene (Bap). The above results were also affected by heating supply patterns (district heating supply and non-district heating supply). There was a positive correlation between microbial community richness and •OH concentration, and microbial community richness decreased as PM specific surface area increased. This work reveals connections between the properties of PMs and the microbial community diversity with heating supply patterns, and gives novel insights to atmospheric health and carbon neutrality.

Diversity and Source of Airborne Microbial Communities at Differential Polluted Sites of Rome

Biogenic fraction of airborne PM10 which includes bacteria, viruses, fungi and pollens, has been proposed as one of the potential causes of the PM10 toxicity. The present study aimed to provide a comprehensive understanding of the microbial community variations associated to PM10, and their main local sources in the surrounding environment in three urban sites of Rome, characterized by differential pollution rate: green area, residential area and polluted area close to the traffic roads. We combined high-throughput amplicon sequencing of the bacterial 16S rRNA gene and the fungal internal transcribed spacer (ITS) region, with detailed chemical analysis of particulate matter sampled from air, paved road surfaces and leaf surfaces of Quercus ilex. Our results demonstrated that bacterial and fungal airborne communities were characterized by the highest alpha-diversity and grouped separately from epiphytic and road dust communities. The reconstruction of source-sink relationships revealed that the resuspension/deposition of road dust from traffic might contribute to the maximum magnitude of microbial exchanges. The relative abundance of extremotolerant microbes was found to be enhanced in epiphytic communities and was associated to a progressively increase of pollution levels as well as opportunistic human pathogenicity in fungal communities.

Operating Room Improvements Based on Environmental Quality Index Risk Prediction can help Reduce Surgical Site Infections

Importance: The role of the operating room (OR) airborne environment in the incidence of surgical site infections (SSI) has ranked behind patient and perioperative team-related factors associated with risk for SSI. Emerging evidence demonstrates that the design and performance of the OR environment impacts the airborne microbiome both within the sterile field and at tables where instruments and implants are exposed. However, the correlation between OR air quality and the risk of SSI continues to be challenged. Objective: To determine if improving the asepsis of the airborne environment in ORs contributes to reduced SSI rates. Design: The performance of air delivery systems in fourteen operating rooms was evaluated using the Environmental Quality Indicator (EQI) risk picture method to identify potential improvements to airflow management that reduce airborne contamination and operating costs. SSI rates for colon and abdominal hysterectomy procedures were tracked in these ORs for 39 months before and after improvements were implemented. SSI rates were also tracked for the same time frame for six control ORs in which no improvements were made. Airborne microbial data was collected. Setting: Twenty ORs in an academic medical center, Midwest USA. A convenience sample of all surgical patients, de-identified, was used in the twenty ORs studied. Results: SSI rate was reduced from 8.4% to 5.7% (p=.0039) in ORs in which improvements were implemented. Reduction of SSI rate in control ORs was not significant (p=.76). Fewer airborne microbes were detected in areas of OR with improvements (p<.0001). Conclusion: Areas for environmental quality improvement in ORs was identified and mapped by relative risk of contamination. Implementation of these improvements resulted in decreased microbial contamination and contributed to significant reduction in surgical site infection.

Microbiological surveillance of air and contact surface of pubic transports with its correlation to human infection risks

Over past few years, people are giving more attention to air pollution and its effects on human health. Due to the high population density in Bangladesh, air pollution is a major issue in metropolitan areas, especially in Dhaka city. Present study aims to isolate air-borne microbes from the inside environment of public transport and different types of microbes that are frequently encountered by commuters when they touch the interior surfaces of vehicles used for public transport in Dhaka City. Atmospheric load of microorganisms was measured with petri dish which was kept open for 30 minutes in the sampling locations and swabs were taken from interior surfaces of vehicles. Air samples collected from both bus and railway stations showed a high atmospheric microbial count (total viable bacteria and total fungal count were 140 to 776 CFU/plate/30 min and 27 to 168 CFU/plate/30 min, respectively). A similar outcome was found after analysis of swab samples of the contact surfaces of the vehicles as well. A total of four bacterial pathogens were identified from the interior surfaces of the vehicle including Escherichia coli, Bacillus spp., Pseudomonas spp. and Vibrio spp. which are known to be associated with gastrointestinal tract infection. To manage and control the environmental health risks caused by air pathogens, an authorized governmental agency should do continuous monitoring of air quality to reduce the negative effects and impacts of air pathogens on human and animal health. This research has shown a great concern to health practitioners in developing countries because these are pathogens that are mostly resistant to the commonly available antibiotics used in the treatment of infection associated with these pathogens. Most importantly, we need to raise awareness among the public in order to reduce the load and spread of pathogenic bacteria in the environment. Stamford Journal of Microbiology, Vol.11 (1) 2021: 7-10

The decay of airborne bacteria and fungi in a constant temperature and humidity test chamber.

Despite substantial research to profile the microbial characteristics in the atmosphere, the changing metabolism underpinning microbial successional dynamics remains ambiguous. Herein, we applied qPCR, high-throughput sequencing of the genes encoding 16S and ITS rRNA to render the bacterial/fungal dynamics of ambient PM2.5 filters maintained at constant conditions of temperature (20±2°C) and humidity (50±5%). The incubation experiments which lasted for 50days aim to simulate a metabolic process of microbe in two types PM2.5 (polluted and non-polluted). The results show that microbial community species in polluted PM2.5 had faster decay rates, more bacterial diversity and less fungal community compared to the non-polluted ones. For bacteria, the proportion of anaerobic species is higher than aerobic ones, and their performance of contain mobile elements, form-biofilms, and pathogenic risks declined rapidly as times went by. Whereas for fungi, saprotroph species occupied about 70% of the population, resulting in a specified peak of abundance due to the adequacy nutrients supplied by the apoptosis cells. Combining the classified microbial species, we found stable community structure and the volatile ones related to the various metabolic survival strategies during different time. Without the input of peripheral environment, the health risks of airborne microbe descend to a healthy level after 20days, implying their biologic effectiveness was about 20days no matter the air is polluted or not. This study provided new insights into the different metabolic survival of airborne microorganisms in ideal and stable conditions.

Novel non intrusive continuous use ZeBox technology to trap and kill airborne microbes

Preventing nosocomial infection is a major unmet need of our times. Existing air decontamination technologies suffer from demerits such as toxicity of exposure, species specificity, noxious gas emission, environment-dependent performance and high power consumption. Here, we present a novel technology called “ZeBox” that transcends the conventional limitations and achieves high microbicidal efficiency. In ZeBox, a non-ionizing electric field extracts naturally charged microbes from flowing air and deposits them on engineered microbicidal surfaces. The surface’s three dimensional topography traps the microbes long enough for them to be inactivated. The electric field and chemical surfaces synergistically achieve rapid inactivation of a broad spectrum of microbes. ZeBox achieved near complete kill of airborne microbes in challenge tests (5–9 log reduction) and >90% efficiency in a fully functional stem cell research facility in the presence of humans. Thus, ZeBox fulfills the dire need for a real-time, continuous, safe, trap-and-kill air decontamination technology.

Effect of Plant-Products Fumigation on Air-Borne Microbes

Background and Objective: Purity of the ambient air is essential for our health and well-being. One of the main factors influencing air quality is the presence of microbes. Fumigation of herbs has been recommended in Unani medicine to purify the air. Hence, the present study was aimed to evaluate the effect of selected Unani herbs fumigation on air-borne microbes.
 Methods: In this study, the effect of fumigation with Unani Medicinal herbs powder on air-borne microbes was assessed using differences in total colony counts of microbes in pre and post fumigation samples. Microbial load in the air was quantified using the passive open-air petri plate method. Formalin and potassium permanganate served as positive control, while tamarind wood charcoal fumigation served as negative control.
 Results: Fumigation with Unani medicinal herbs powder at a dose of 45 grams was found to be the most effective in reducing the microbial load of the air. Significant reduction in aerial microbial colonies was observed with fumigation at 30 and 45 gms in the fumigated areas (P<0.05).
 Conclusion: It can be inferred from the findings of the present study that the test drugs fumigation efficiently reduces the air-borne microbes, hence may be recomanded for air disnfectant. However, various factors that were not considered in this study, such as the effect of temperature and humidity on disinfection efficiency of fumigants should be addressed in further studies.

The concentration, size distribution and dry deposition flux of microbes in atmospheric aerosols over the marginal seas and Northwest Pacific Ocean

The concentration and flux of biological aerosol particles over oceans are important for understanding the ecological implications of airborne microbes in marine ecosystems. Airborne microbes over oceans remain uncharacterized, especially the difference between those over the marginal seas and those over the open oceans. Atmospheric aerosol samples were collected over Qingdao (QD), the Yellow and Bohai Seas (YBS) and the Northwest Pacific Ocean (NWPO) during three cruises in the spring of 2014 and 2016. The total airborne microbes (TAM) in the samples were assessed based on microscope counts. The TAM concentration was (4.07 ± 1.42) × 105 cells·m−3 and (2.75 ± 0.91) × 105 cells·m−3 over the NWPO in 2014 and 2016, respectively, significantly lower than that over QD ((8.02 ± 4.04) × 105 cells·m−3 and (14.04 ± 23.95) × 105 cells·m−3 in 2014 and 2016, respectively) due to the continental source of microbes, but the TAM concentration over the NWPO in 2014 was significantly higher than that over the YBS (p < 0.01). The microbe concentration over the NWPO was affected by wind speed and direction, the horizontal offshore distance and the ratio of the distance over the sea to the total transport distance (RS), but the microbe concentration over the YBS was affected by air temperature, NO, NO2, the distance over the sea, the horizontal offshore distance and RS. Compared with those in the marine samples, the TAM in coastal samples was affected by many factors, such as air temperature, relative humidity, atmospheric pressure, PM2.5, PM10, SO2 and O3. A dust event significantly increased the concentration of TAM by a factor of 1.6–49 and changed the size distribution of TAM in the samples. The dry deposition flux of TAM was 8.83 × 107–5.12 × 108 cells·m−2·d−1 over the NWPO, close to the flux of 1.20 × 108–2.63 × 108 cells·m−2·d−1 over the YBS. Our results suggest that airborne microbes are input to the ocean via atmospheric deposition, which may have important impacts on marine ecosystems.

Comments on the Discussion Forum: Oromucosal immunomodulation as clinical spectrum mitigating factor in SARS-CoV-2 infection.

The mammalian lactoperoxidase system, consisting of lactoperoxidase and the H2O2‐producing enzyme duox, is our first line of defence against airborne microbes. This system catalyses the production of hypoiodite and hypoiodous acid in the presence of sufficient iodine. These products are highly efficient at destroying the H1N1 virus and the respiratory syncytial virus (RSV). Japan has not been affected as much as other nations during the COVID‐19 pandemic (death rate about 10% of the United States), and we think this is due to a diet high in iodine. With this in mind, we suggest four actions to prevent SARS‐CoV‐2 infections. First, health professionals should study the preventative effect of increasing iodine in the diets of the aged, institutionalized, diabetics andsmokers. Second, the recommended daily intake (RDI) for iodine should be significantly increased, to at least double, the current RDI. Governments should encourage the use and distribution of cheap iodized salts, kelp and seaweed. Third, more research should be done around the physiology and the protective effects of the lactoperoxidase system. Finally, the degradation products of the SARS‐CoV‐2 viral particle by hypoiodite and hypoiodous acid should be characterized; portions of the damaged particle are likely to elicit stronger immunity and better vaccines.

The Toxicity of Wiped Dust and Airborne Microbes in Individual Classrooms Increase the Risk of Teachers' Work-Related Symptoms: A Cross-Sectional Study.

Background: The causes and pathophysiological mechanisms of building-related symptoms (BRS) remain open. Objective: We aimed to investigate the association between teachers’ individual work-related symptoms and intrinsic in vitro toxicity in classrooms. This is a further analysis of a previously published dataset. Methods: Teachers from 15 Finnish schools in Helsinki responded to the symptom survey. The boar sperm motility inhibition assay, a sensitive indicator of mitochondrial dysfunction, was used to measure the toxicity of wiped dust and cultured microbial fallout samples collected from the teachers’ classrooms. Results: 231 teachers whose classroom toxicity data had been collected responded to the questionnaire. Logistic regression analysis adjusted for age, gender, smoking, and atopy showed that classroom dust intrinsic toxicity was statistically significantly associated with the following 12 symptoms reported by teachers (adjusted ORs in parentheses): nose stuffiness (4.1), runny nose (6.9), hoarseness (6.4), globus sensation (9.0), throat mucus (7.6), throat itching (4.4), shortness of breath (12.2), dry cough (4.7), wet eyes (12.7), hypersensitivity to sound (7.9), difficulty falling asleep (7.6), and increased need for sleep (7.7). Toxicity of cultured microbes was found to be associated with nine symptoms (adjusted ORs in parentheses): headache (2.3), nose stuffiness (2.2), nose dryness (2.2), mouth dryness (2.8), hoarseness (2.2), sore throat (2.8), throat mucus (2.3), eye discharge (10.2), and increased need for sleep (3.5). Conclusions: The toxicity of classroom dust and airborne microbes in boar sperm motility inhibition assay significantly increased teachers’ risk of work-related respiratory and ocular symptoms. Potential pathophysiological mechanisms of BRS are discussed.

Microbial Air Samplers for Meaningful Cleanroom Environmental Monitoring

Airborne microbiological concentrations within pharmaceutical cleanrooms are determined by sampling and to maximise the detection of any airborne microbes, it is essential that the sampling is undertaken in locations where there is greatest contamination risk using air samplers that have a verified and appropriate performance. Sampler performance can be assessed by review of both the physical and biological collection efficiencies that are determined by testing. The physical collection efficiency is the ability to collect particles of various sizes and the biological collection efficiency assesses the collection of viable microbes that includes the losses caused by the physical collection efficiency and the detrimental effect that the sampling has on the viability of the captured microbes. Due to the limitations of the established biological collection efficiency test method, this efficiency is only determined for microbes of sub-micron size which are not representative of the larger microbe-carrying particles typically present with cleanrooms. Samplers with a low physical collection efficiency for sub-micron particles are likely to have a poor performance when this test method is utilised and in an attempt to remove this bias from the testing the ‘biological efficiency’, is often reported. This is a measure of the likelihood that any captured microbes would survive, but is often mistaken for the biological collection efficiency and samplers may be utilised in the false belief that they have an appropriate performance. This article provides information regarding air sampler performance testing and reviews the test results reported by the same independent specialist testing company, therefore negating issues resulting from different testing methods, for three different air samplers. The results that are used to determine the ‘biological efficiency’ are examined to provide information relating to the biological collection efficiency of each sampler and to also provide additional information relating to the physical collection efficiency. Improvements to enhance the air sampler testing procedures, to enable a better direct comparison of the performance of different samplers, are suggested.

General decline in the diversity of the airborne microbiota under future climatic scenarios

Microorganisms attached to aerosols can travel intercontinental distances, survive, and further colonize remote environments. Airborne microbes are influenced by environmental and climatic patterns that are predicted to change in the near future, with unknown consequences. We developed a new predictive method that dynamically addressed the temporal evolution of biodiversity in response to environmental covariates, linked to future climatic scenarios of the IPCC (AR5). We fitted these models against a 7-year monitoring of airborne microbes, collected in wet depositions. We found that Bacteria were more influenced by climatic variables than by aerosols sources, while the opposite was detected for Eukarya. Also, model simulations showed a general decline in bacterial richness, idiosyncratic responses of Eukarya, and changes in seasonality, with higher intensity within the worst-case climatic scenario (RCP 8.5). Additionally, the model predicted lower richness for airborne potential eukaryotic (fungi) pathogens of plants and humans. Our work pioneers on the potential effects of environmental variability on the airborne microbiome under the uncertain context of climate change.

The Response of Airborne Mycobiome to Dust Storms in the Eastern Mediterranean

Airborne microbial communities directly impact the health of humans, animals, plants, and receiving ecosystems. While airborne bacterial and fungal communities have been studied by both cultivation-based methods and metabarcoding surveys targeting specific molecular markers, fewer studies have used shotgun metagenomics to study the airborne mycobiome. We analyzed the diversity and relative abundance of fungi in nine airborne metagenomes collected on clear days (“background”) and during dust storms in the Eastern Mediterranean. The negative correlation between the relative abundance of fungal reads and the concentrations of atmospheric particulate matter having an aerodynamic diameter smaller than 10 μm (PM10) indicate that dust storms lower the proportion of fungi in the airborne microbiome, possibly due to the lower relative abundance of fungi in the dust storm source regions and/or more effective transport of bacteria by the dust. Airborne fungal community composition was altered by the dust storms, particularly those originated from Syria, which was enriched with xerophilic fungi. We reconstructed a high-quality fungal metagenome-assembled genome (MAG) from the order Cladosporiales, which include fungi known to adapt to environmental extremes commonly faced by airborne microbes. The negative correlation between the relative abundance of Cladosporiales MAG and PM10 concentrations indicate that its origin is dominated by local sources and likely includes the indoor environments found in the city.

Real-time Monitoring of Bioaerosol in a Residential Property in Central Tokyo

Real-time onsite monitoring of indoor airborne microbes in a residential property in central Tokyo was carried out in 2020 and 2021, following the onset of the COVID-19 pandemic. A microbial sensor utilizing fluorescence emitted by microorganisms was used to measure bioaerosol concentrations in the living room and children’s bedroom as well as on the balcony. Indoor PM2.5 was also monitored simultaneously at certain time points using a PM2.5 sensor. The behavior of the residents was also recorded during some monitoring periods. The average number concentration of microbes as fungi in the living room was 15,100, 58,800, and 10,600 counts m−3 in spring, summer, and winter, respectively, increasing in summer when the outside temperature was high. Microbial number concentrations were closely related to human behavior, increasing rapidly during periods of physical activity, but decreasing again within 20–30 min of the activity ending. There was no clear correlation between indoor microbial number concentrations and PM2.5 concentrations, suggesting that indoor microorganisms are concentrated in coarse particles, such as dust, which are quickly removed via gravitational settling. The concentration of indoor airborne microorganisms decreased significantly after ventilation, and although an occasional increase was observed immediately after ventilation, concentrations decreased again rapidly within 10–20 min. These results suggest that even a short period of ventilation can significantly reduce the indoor bioaerosol.