Bacterial pathogens were detected from human exhaled breath using a novel protocol

The Effect of Face Mask Wear on the Ocular Surface and Contact Lens Microbiome

OBJECTIVES

As face mask wear can result in the redirection of nasal and oral exhalation toward the ocular region, this study investigated the impact of face mask wear on the conjunctiva, eyelid margin, and contact lens (CL) surface microbiome.

METHODS

In this prospective, cross-over study, experienced CL wearers (N=20) were randomized to wear a face mask for 6 hr/day (minimum) for a week or no mask for a week. The conjunctiva, eyelid, and CLs were then sampled. After a 1-week washout period, participants were crossed over into the alternate treatment for 1 week and sampling was repeated. Sampling was bilateral and randomly assigned to be processed for culturing or 16S ribosomal(r) RNA gene sequencing.

RESULTS

Culturing showed no effect of mask wear on the average number of bacterial colonies isolated on the conjunctiva, eyelid, or CL, but there was increased isolation of Staphylococcus capitis on CL samples with mask wear (P=0.040). Culture-independent sequencing found differences in the taxonomic complexity and bacterial composition between the three sites (P<0.001), but there was no effect of bacterial diversity within and between sites. Mask wear did not impact dry eye or CL discomfort, but increased ocular surface staining was reported (P=0.035).

CONCLUSIONS

Mask wear did not substantially alter the microbiome of the conjunctiva, eyelid margin, or CL surfaces in uncompromised healthy eyes.

Online monitoring system for qualitative and quantitative analysis of bioaerosols by combined ATP bioluminescence assay with loop-mediated isothermal amplification

Rapid detection of airborne pathogens is crucial in preventing respiratory infections and allergies. However, technologies aiming to real-time analysis of microorganisms in air remain limited due to the sparse and complex nature of bioaerosols. Here, we introduced an online bioaerosol monitoring system (OBMS) comprised of integrated units including a rotatable stainless-steel sintered filter-based sampler, a lysis unit for extracting adenosine triphosphate (ATP), and a single photon detector-based fluorescence unit. Through optimization of the ATP bioluminescence method and establishment of standard curves between relative luminescence units (RLUs) and ATP as well as microbial concentration, we achieved simultaneous detection of bioaerosols' concentration and activity. Testing OBMS with four bacterial and two fungal aerosols at a sampling flow rate of 10 to 50 L/min revealed an outstanding collection efficiency of 95 % at 30 L/min. A single OBMS measurement takes only 8 min (sampling: 5 min; lysis and detection: 3 min) with detection limits of 3 Pcs/ms photons (2.9 × 103 and 292 CFU/m3 for Staphylococcus aureus and Candida albicans aerosol). In both laboratory and field tests, OBMS detected higher concentrations of bioaerosol compared to the traditional Andersen impactor and liquid biosampler. When combined OBMS with loop-mediated isothermal amplification (LAMP), the bioaerosol can be qualitative and quantitative analyzed within 40 min without the cumbersome procedures of sample pretreatment and DNA extraction. These results offer a high compressive and humidity resistance membrane filtration sampler and validate the potential of OBMS for online measurement of bioaerosol concentration and composition.

Three dimensional analysis of the exhalation flow in the proximity of the mouth

The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.

Advancements in Rapid and Affordable Diagnostic Testing for Respiratory Infectious Diseases: Evaluation of Aptamer Beacon Technology for Rapid and Sensitive Detection of SAR-CoV-2 in Breath Condensate

The demand for rapid and efficient diagnostic point-of-care tests for respiratory infectious diseases has become increasingly critical in the current landscape. The emphasis on accessibility has been underscored over the past year, making it crucial to have biological components that exhibit fast and accurate kinetics. The foundation for precise, swift, and effective testing relies on the availability of highly responsive biological agents. Two published aptamer DNA sequences designated Song and MSA52 and their truncated internal stem-loop structures were studied for their potential to serve as aptamer beacons for rapid COVID detection. The candidate beacons were covalently labeled with Atto 633 dye attached to their 5' ends and Iowa Black quencher attached to their 3' ends. The whole aptamer structures exhibited the greatest fluorescence signal intensities and higher fluorescence background than their truncated internal stem-loop beacon structures suggesting that the distance between fluorophores and quenchers was greater for the whole aptamer beacon candidates versus the isolated stem-loop structures. Beacon candidates were tested against two heat- or gamma radiation-killed SARS-CoV-2 Washington 1/2020 virus samples and three different COVID spike (S) proteins to test their effectiveness. Despite the higher background fluorescence, the whole aptamer beacons showed better signal-to-noise ratios and were selected for further investigation. Limit of detection (LOD) studies revealed that both the whole Song and whole MSA52 aptamer beacon candidates had a LOD of 9.61 × 103 genome equivalents in phosphate-buffered saline using the red channel of a Promega Quantus™ fluorometer which correlated well with confirmatory spectrofluorometry. Cross-reactivity studies using numerous COVID variants, related coronaviruses, and other common respiratory pathogens suggested greater COVID selectivity for the whole MSA52 versus the whole Song aptamer beacon candidate, indicating promise for specific COVID detection. Importantly, both whole aptamer beacon candidates exhibited very rapid "bind and detect" fluorescence increases within the first 1-2 min of mixing the beacons with killed SARS-CoV-2 viruses in 100 µl samples. Overall, this work illustrates the strong potential for aptamer beacons for rapid, on-site detection and presumptive diagnosis of COVID in breath condensates or other small liquid samples. This research highlights the strong potential of aptamer beacons for addressing the need for fast and convenient diagnostic tools in global health contexts, especially in resource-limited settings.

Inactivation of airborne pathogenic microorganisms by plasma-activated nebulized mist

The airborne microorganisms in the aerosols are one main transmission way of pathogenic microorganisms and therefore inactivation of microorganisms in aerosols could effectively prevent the transmission of pathogenic microorganisms to control epidemics. The mist nebulized by plasma-activated air could effectively inactivate bacteria and could be developed for the sterilization of microorganisms in aerosols. In this study, the plasma-activated nebulized mist (PANM) was applied for the inactivation of microorganisms in aerosols and efficiently inactivated the bacteria, yeast, and viruses in aerosols after 2-min treatment. The PANM treatment caused morphologic changes and damage to the bacteria cells in aerosols. The PANM could also inactivate the microorganisms attached to the surface of the treatment chamber and the bacteria attached to the skin of mice within 6-min treatment. The biosafety assays demonstrated that the PANM treatment exhibited no effects on the behavior, hematological and serum biochemical parameters of blood, and organs from the mice. This study would supply an efficient, broad-spectrum, and safe aerosol sterilization strategy based on plasma technology to prevent the transmission of airborne microorganisms.

A safer framework to evaluate characterization technologies of exhaled biologic materials using electrospun nanofibers

Exhaled biologic material is the source for the spread of many respiratory tract infections. To avoid the high-level of biosafety required to manage dangerous pathogens, we developed a safer framework using the endogenous surrogate targets RNase P and Streptococcus mitis as a means to sample exhaled biologics. Our exhalation collection scheme uses nanoscale fibrous poly(vinyl alcohol) substrates as facemask inserts. After a period of breathing or speaking, the inserts are removed and dissolved. RNase P RNA and S. mitis DNA are extracted for quantification by multiplexed RT-qPCR. Both surrogate biomarkers were detected in all samples obtained during breathing for at least five minutes or speaking for one minute. Phrases repeated 30 times had the most copies with 375 ± 247 of S. mitis and 54 ± 33 of RNase P. When the phrases were repeated just 5 times, the S. mitis copies collected were still detectable but at a significantly lower level of 11 ± 5 for S. mitis and 12 ± 9 for RNase P. These results demonstrate a collection and quantification framework that can be readily adapted to further characterize the exhalation of nanoscale biologic materials from healthy individuals, explore new collection designs safely, and serve as a method to incorporate sample controls for future pathogen exhalation studies.

Microstructural evaluation and recommendations for face masks in community use to reduce the transmission of respiratory infectious diseases

BACKGROUND AND OBJECTIVE

Recommendations for the use of face masks to prevent and protect against the aerosols (≤5µm) and respiratory droplet particles (≥5µm), which can carry and transmit respiratory infections including severe acute respiratory syndrome coronavirus (SARS-CoV-2), have been in effect since the early stages of the coronavirus disease 2019 (COVID-19). The particle filtration efficiency (PFE) and air permeability are the most crucial factors affecting the level of pathogen transmission and breathability, i.e. wearer comfort, which should be investigated in detail.

METHODS

In this context, this article presents a novel assessment framework for face masks combining X-ray microtomography and computational fluid dynamics simulations. In consideration to their widespread public use, two types of face masks were assessed: (I) two layer non-woven face masks and (II) the surgical masks (made out of a melt-blown fabric layer covered with two non-woven fabric layers).

RESULTS

The results demonstrate that the surgical masks provide PFEs over 75% for particles with diameter over 0.1µm while two layer face masks are found out to have insufficient PFEs, even for the particles with diameter over 2µm (corresponding PFE is computed as 47.2%). Thus, existence of both the non-woven fabric layers for mechanical filtration and insertion of melt-blown fabric layer(s) for electrostatic filtration in the face masks were found to be highly critical to prevent the airborne pathogen transmission.

CONCLUSIONS

The present framework would assist in computational assessment of commonly used face mask types based on their microstructural characteristics including fiber diameter, orientation distributions and fiber network density. Therefore, it would be also possible to provide new yet feasible design routes for face masks to ensure reliable personal protection and optimal breathability.

Roles for Pathogen Interference in Influenza Vaccination, with Implications to Vaccine Effectiveness (VE) and Attribution of Influenza Deaths

Pathogen interference is the ability of one pathogen to alter the course and clinical outcomes of infection by another. With up to 3000 species of human pathogens the potential combinations are vast. These combinations operate within further immune complexity induced by infection with multiple persistent pathogens, and by the role which the human microbiome plays in maintaining health, immune function, and resistance to infection. All the above are further complicated by malnutrition in children and the elderly. Influenza vaccination offers a measure of protection for elderly individuals subsequently infected with influenza. However, all vaccines induce both specific and non-specific effects. The specific effects involve stimulation of humoral and cellular immunity, while the nonspecific effects are far more nuanced including changes in gene expression patterns and production of small RNAs which contribute to pathogen interference. Little is known about the outcomes of vaccinated elderly not subsequently infected with influenza but infected with multiple other non-influenza winter pathogens. In this review we propose that in certain years the specific antigen mix in the seasonal influenza vaccine inadvertently increases the risk of infection from other non-influenza pathogens. The possibility that vaccination could upset the pathogen balance, and that the timing of vaccination relative to the pathogen balance was critical to success, was proposed in 2010 but was seemingly ignored. Persons vaccinated early in the winter are more likely to experience higher pathogen interference. Implications to the estimation of vaccine effectiveness and influenza deaths are discussed.

Reducing the Effectiveness of Ward Particulate Matter, Bacteria and Influenza Virus by Combining Two Complementary Air Purifiers

Air purifiers should pay much attention to hospital-associated infections, but the role of a single air purifier is limited. The goal of this study was to evaluate the effectiveness of the combined application of the nonequilibrium positive and negative oxygen ion purifier (PNOI) and the high-efficiency particulate air filter (HEPA) on a complex, polluted environment. Two of the better performing purifiers were selected before the study. The efficacy of their use alone and in combination for purification of cigarette particulate matter (PM), Staphylococcus albicans, and influenza virus were then evaluated under a simulated contaminated ward. PNAI and HEPA alone are deficient. However, when they were combined, they achieved 98.44%, 99.75%, and 100% 30 min purification rates for cigarette PM, S. albus, and influenza virus, respectively. The purification of pollution of various particle sizes and positions was optimized and reduced differentials, and a subset of airborne influenza viruses is inactivated. Furthermore, they were superior to ultraviolet disinfection for microbial purification in air. This work demonstrates the strong purification capability of the combined application of these two air purifiers for complex air pollution, which provides a new idea for infection control in medical institutions.

Nanomaterials and metal-organic frameworks for biosensing applications of mutations of the emerging viruses

The world today lives in a state of terrible fear due to the mutation of the emerging COVID-19. With the continuation of this pandemic, there is an urgent need for fast, accurate testing devices to detect the emerging SARS-CoV-2 pandemic in terms of biosensors and point-of-care testing. Besides, the urgent development in personal defense tools, anti-viral surfaces and wearables, and smartphones open the door for simplifying the self-diagnosis process everywhere. This review introduces a quick COVID-19 overview: definition, transmission, pathophysiology, the identification and diagnosis, mutation and transformation, and the global situation. It also focuses on an overview of the rapidly advanced technologies based on nanomaterials and MOFs for biosensing, diagnosing, and viral control of the SARS-CoV-2 pandemic. Finally, highlight the latest technologies, applications, existing achievements, and preventive diagnostic strategies to control this epidemic and combat the emerging coronavirus. This humble effort aims to provide a helpful survey that can be used to develop a creative solution and to lay down the future vision of diagnosis against COVID-19.

Metabolic profile of exhaled breath condensate from the pneumonia patients

PURPOSE OF THE STUDY

Exhaled breath condensate (EBC) is increasingly being used for disease diagnosis and environmental exposure assessment as a noninvasive method reducing the risk of exposure. The purpose of this study was to investigate the application of a new sample type of EBC in pneumonia by metabolomics and to explore differential metabolites and potential metabolic pathways.

MATERIALS AND METHODS

A case-control study was performed at the Peking University Third Hospital from August to December 2020. C-MS/MS analyses were performed on EBC samples using a UHPLC system.

RESULTS

Totally 22 patients with pneumonia and 24 healthy controls were recruited. Using untargeted metabolomics based on LC-MS/MS analysis, 25 kinds of differential metabolites were found. Through a comprehensive analysis of the pathways in which the differential metabolites were located, the key pathway with the highest correlation with the difference of metabolites was taurine and hypotaurine metabolism.

CONCLUSIONS

The study implicates that the hypotaurine/taurine metabolic pathway may play a role on the development of pneumonia through metabolism analysis on EBC and the 3-Sulfinoalanine may be used as a biomarker in the diagnosis of pneumonia.

Insights into the Profile of the Human Expiratory Microbiota and Its Associations with Indoor Microbiotas

Microorganisms residing in the human respiratory tract can be exhaled, and they constitute a part of environmental microbiotas. However, the expiratory microbiota community and its associations with environmental microbiotas remain poorly understood. Here, expiratory bacteria and fungi and the corresponding microbiotas from the living environments were characterized by DNA amplicon sequencing of residents' exhaled breath condensate (EBC) and environmental samples collected from 14 residences in Nanjing, China. The microbiotas of EBC samples, with a substantial heterogeneity, were found to be as diverse as those of skin, floor dust, and airborne microbiotas. Model fitting results demonstrated the role of stochastic processes in the assembly of the expiratory microbiota. Using a fast expectation-maximization algorithm, microbial community analysis revealed that expiratory microbiotas were differentially associated with other types of microbiotas in a type-dependent and residence-specific manner. Importantly, the expiratory bacteria showed a composition similarity with airborne bacteria in the bathroom and kitchen environments with an average of 12.60%, while the expiratory fungi showed a 53.99% composition similarity with the floor dust fungi. These differential patterns indicate different relationships between expiratory microbiotas and the airborne microbiotas and floor dust microbiotas. The results here illustrated for the first time the associations between expiratory microbiotas and indoor microbiotas, showing a potential microbial exchange between the respiratory tract and indoor environment. Thus, improved hygiene and ventilation practices can be implemented to optimize the indoor microbial exposome, especially in indoor bathrooms and kitchens.

SARS-CoV-2 aerosol transmission and detection

Aerosol transmission has been officially recognized by the world health authority resulting from its overwhelming experimental and epidemiological evidences. Despite substantial progress, few additional actions were taken to prevent aerosol transmission, and many key scientific questions still await urgent investigations. The grand challenge, the effective control of aerosol transmission of COVID-19, remains unsolved. A better understanding of the viral shedding into the air has been developed, but its temporal pattern is largely unknown. Sampling tools, as one of the critical elements for studying SARS-CoV-2 aerosol, are not readily available around the world. Many of them are less capable of preserving the viability of SARS-CoV-2, thus offering no clues about viral aerosol infectivity. As evidenced, the viability of SARS-CoV-2 is also directly impacted by temperature, humidity, sunlight, and air pollutants. For SARS-CoV-2 aerosol detection, liquid samplers, together with real-time polymerase chain reaction (RT-PCR), are currently used in certain enclosed or semi-enclosed environments. Sensitive and rapid COVID-19 screening technologies are in great need. Among others, the breath-borne-based method emerges with global attention due to its advantages in sample collection and early disease detection. To collectively confront these challenges, scientists from different fields around the world need to fight together for the welfare of mankind. This review summarized the current understanding of the aerosol transmission of SARS-CoV-2 and identified the key knowledge gaps with a to-do list. This review also serves as a call for efforts to develop technologies to better protect the people in a forthcoming reopening world.

Identification of Microorganisms Dwelling on the 19th Century Lanna Mural Paintings from Northern Thailand Using Culture-Dependent and -Independent Approaches

Simple Summary

In this study, we compared microbial communities in Lanna mural paintings in temples with different numbers of visitors using culture-dependent and culture independent approaches. The results showed that microorganisms could damage the colors that are used on murals. The process of degradation involved the production of organic acids and formation of the calcium crystal. Furthermore, we found that the site with higher number of visitors is associated with microbial contamination from humans while the site with lower number of visitors had higher saprotroph population. Further research into these microorganisms, their activities and functional roles may provide crucial information to aid the preservation of mural paintings.

Abstract

Lanna painting is a unique type of painting in many temples in the Northern Thai region. Similar to most mural paintings, they usually decay over time partly due to the activity of microbes. This study aimed to investigate the microorganisms from two Lanna masterpiece paintings in two temples that differ in the numbers of visitors using both culture-dependent and -independent approaches. The microorganisms isolated from the murals were also tested for the biodeterioration activities including discoloration, acid production and calcium precipitation. Most microorganisms extracted from the paintings were able to discolor the paints, but only fungi were able to discolor, produce acids and precipitate calcium. The microorganism communities, diversity and functional prediction were also investigated using the culture-independent method. The diversity of microorganisms and functional prediction were different between the two temples. Gammaproteobacteria was the predominant group of bacteria in both temples. However, the fungal communities were different between the two temples as Aspergillus was the most abundant genus in the site with higher number of visitors [Buak Krok Luang temple (BK)]. Conversely, mural paintings at Tha Kham temple (TK) were dominated by the Neodevriesia genera. We noticed that a high number of visitors (Buak Krok Luang) was correlated with microbial contamination from humans while the microbial community at Tha Kham temple had a higher proportion of saprotrophs. These results could be applied to formulate a strategy to mitigate the amount of tourists as well as manage microorganism to slow down the biodeterioration process.

SARS-CoV-2, other respiratory viruses and bacteria in aerosols: Report from Kuwait's hospitals

The role of airborne particles in the spread of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is well explored. The novel coronavirus can survive in aerosol for extended periods, and its interaction with other viral communities can cause additional virulence and infectivity. This baseline study reports concentrations of SARS-CoV-2, other respiratory viruses, and pathogenic bacteria in the indoor air from three major hospitals (Sheikh Jaber, Mubarak Al-Kabeer, and Al-Amiri) in Kuwait dealing with coronavirus disease 2019 (COVID-19) patients. The indoor aerosol samples showed 12-99 copies of SARS-CoV-2 per m3 of air. Two non-SARS-coronavirus (strain HKU1 and NL63), respiratory syncytial virus (RSV), and human bocavirus, human rhinoviruses, Influenza B (FluB), and human enteroviruses were also detected in COVID-positive areas of Mubarak Al Kabeer hospital (MKH). Pathogenic bacteria such as Mycoplasma pneumonia, Streptococcus pneumonia and, Haemophilus influenza were also found in the hospital aerosols. Our results suggest that the existing interventions such as social distancing, use of masks, hand hygiene, surface sanitization, and avoidance of crowded indoor spaces are adequate to prevent the spread of SARS-CoV-2 in enclosed areas. However, increased ventilation can significantly reduce the concentration of SARS-CoV-2 in indoor aerosols. The synergistic or inhibitory effects of other respiratory pathogens in the spread, severity, and complexity of SARS-CoV-2 need further investigation.

Rapid visualization and detection of Staphylococcus aureus based on loop-mediated isothermal amplification

Staphylococcus aureus is a common clinical bacterial pathogen that can cause a diverse range of infections. The establishment of a rapid and reliable assay for the early diagnosis and detection of S. aureus is of great significance. In this study, we developed a closed-tube loop-mediated isothermal amplification (LAMP) assay for the visual detection of S. aureus using the colorimetric indicator hydroxy naphthol blue (HNB). The LAMP reaction was optimized by adjusting the amplification temperature, the concentrations of Mg²⁺, dNTP, and HNB, and the incubation time. In the optimized reaction system, the specificity of LAMP for S. aureus was 100%. The results established that this method accurately identified S. aureus, with no cross-reactivity with 14 non-S. aureus strains. The limit of detection (LOD) of LAMP was 8 copies/reaction of purified plasmid DNA or 400 colony-forming units/reaction of S. aureus. Compared with conventional PCR, LAMP lowered the LOD by tenfold. Finally, 220 clinically isolated strains of S. aureus and 149 non-S. aureus strains were used to evaluate the diagnostic efficacy of LAMP (test accuracy, 99.46%). The findings indicated that LAMP is a reliable test for S. aureus and could be a promising tool for the rapid diagnosis of S. aureus infections.

Advances in airborne microorganisms detection using biosensors: A critical review

Humanity has been facing the threat of a variety of infectious diseases. Airborne microorganisms can cause airborne infectious diseases, which spread rapidly and extensively, causing huge losses to human society on a global scale. In recent years, the detection technology for airborne microorganisms has developed rapidly; it can be roughly divided into biochemical, immune, and molecular technologies. However, these technologies still have some shortcomings; they are time-consuming and have low sensitivity and poor stability. Most of them need to be used in the ideal environment of a laboratory, which limits their applications. A biosensor is a device that converts biological signals into detectable signals. As an interdisciplinary field, biosensors have successfully introduced a variety of technologies for bio-detection. Given their fast analysis speed, high sensitivity, good portability, strong specificity, and low cost, biosensors have been widely used in environmental monitoring, medical research, food and agricultural safety, military medicine and other fields. In recent years, the performance of biosensors has greatly improved, becoming a promising technology for airborne microorganism detection. This review introduces the detection principle of biosensors from the three aspects of component identification, energy conversion principle, and signal amplification. It also summarizes its research and application in airborne microorganism detection. The new progress and future development trend of the biosensor detection of airborne microorganisms are analyzed.

Nucleic acid detection and quantitative analysis of influenza virus using exhaled breath condensate

Exhaled breath condensate (EBC) is increasingly being used as a non-invasive method for disease diagnosis and environmental exposure assessment. We previously detected the nucleic acids of bacterial pathogens in EBC. Influenza viruses can be transmitted through aerosols during coughing and exhaling. Existing detection methods for influenza have various limitations. The EBC collection method is convenient, non-invasive, and reduces the risk of exposure. We investigated the detection of influenza virus in EBC using a sensitive nucleic acid testing method and performed quantitative analysis to evaluate the present and content of influenza virus in the breath. We evaluated 30 patients with respiratory tract infection during the 2019 influenza season. The clinical data and samples of nasal swabs were collected for rapid influenza diagnostic (antigen) tests. Pharyngeal swab and EBC samples were used for influenza virus nucleic acid detection. Each EBC sample was assessed twice as well as at one-month follow-up of the patients. The nucleic acid test in the EBC of 30 cases revealed 20 and two cases of influenza A and B, respectively, giving a detection rate of 73.3%. The rapid influenza diagnostic (antigen) tests revealed four and 12 cases of influenza A and B, respectively, with a detection rate of 53.3%. All pharyngeal swab samples evaluated by the nucleic acid test were influenza-positive; 12 cases were positive for both influenza A and B and 18 cases were positive for influenza B alone. The influenza viral load in the EBC was 10³-10⁷ copies ml^-1. Among the 16 patients followed-up after 1 month, 4 were positive (25%) in EBC samples and 10 were positive (62.5%) in pharyngeal swab samples. It was preliminary exploration that influenza virus could be detected in EBC. EBC is one of the sample types that would be used for molecular diagnosis of influenza.

Particle sizes of infectious aerosols: implications for infection control

The global pandemic of COVID-19 has been associated with infections and deaths among health-care workers. This Viewpoint of infectious aerosols is intended to inform appropriate infection control measures to protect health-care workers. Studies of cough aerosols and of exhaled breath from patients with various respiratory infections have shown striking similarities in aerosol size distributions, with a predominance of pathogens in small particles (<5 μm). These are immediately respirable, suggesting the need for personal respiratory protection (respirators) for individuals in close proximity to patients with potentially virulent pathogens. There is no evidence that some pathogens are carried only in large droplets. Surgical masks might offer some respiratory protection from inhalation of infectious aerosols, but not as much as respirators. However, surgical masks worn by patients reduce exposures to infectious aerosols to health-care workers and other individuals. The variability of infectious aerosol production, with some so-called super-emitters producing much higher amounts of infectious aerosol than most, might help to explain the epidemiology of super-spreading. Airborne infection control measures are indicated for potentially lethal respiratory pathogens such as severe acute respiratory syndrome coronavirus 2.

On airborne transmission and control of SARS-Cov-2

The COVID-19 pandemic is creating a havoc situation across the globe that modern society has ever seen. Despite of their paramount importance, the transmission routes of SARS-Cov-2 still remain debated among various sectors. Evidences compiled here strongly suggest that the COVID-19 could be transmitted via air in inadequately ventilated environments. Existing experimental data showed that coronavirus survival was negatively impacted by ozone, high temperature and low humidity. Here, regression analysis showed that the spread of SARS-Cov-2 was reduced by increasing ambient ozone concentration level from 48.83 to 94.67 μg/m³ (p-value = 0.039) and decreasing relative humidity from 23.33 to 82.67% (p-value = 0.002) and temperature from -13.17 to 19 °C) (p-value = 0.003) observed for Chinese cities during Jan-March 2020. Besides using these environmental implications, social distancing and wearing a mask are strongly encouraged to maximize the fight against the COVID-19 airborne transmission. At no other time than now are the scientists in various disciplines around the world badly needed by the society to collectively confront this disastrous pandemic.

Demystifying the mist: Sources of microbial bioload in dental aerosols

The risk of transmitting airborne pathogens is an important consideration in dentistry and has acquired special significance in the context of recent respiratory disease epidemics. The purpose of this review, therefore, is to examine (1) what is currently known regarding the physics of aerosol creation, (2) the types of environmental contaminants generated by dental procedures, (3) the nature, quantity, and sources of microbiota in these contaminants and (4) the risk of disease transmission from patients to dental healthcare workers. Most dental procedures that use ultrasonics, handpieces, air‐water syringes, and lasers generate sprays, a fraction of which are aerosolized. The vast heterogeneity in the types of airborne samples collected (spatter, settled aerosol, or harvested air), the presence and type of at‐source aerosol reduction methods (high‐volume evacuators, low volume suction, or none), the methods of microbial sampling (petri dishes with solid media, filter paper discs, air harvesters, and liquid transport media) and assessment of microbial bioload (growth conditions, time of growth, specificity of microbial characterization) are barriers to drawing robust conclusions. For example, although several studies have reported the presence of microorganisms in aerosols generated by ultrasonic scalers and high‐speed turbines, the specific types of organisms or their source is not as well studied. This paucity of data does not allow for definitive conclusions to be drawn regarding saliva as a major source of airborne microorganisms during aerosol generating dental procedures. Well‐controlled, large‐scale, multi center studies using atraumatic air harvesters, open‐ended methods for microbial characterization and integrated data modeling are urgently needed to characterize the microbial constituents of aerosols created during dental procedures and to estimate time and extent of spread of these infectious agents.

Optimal fluorescent-dye staining time for the real-time detection of microbes: a study of Saccharomyces cerevisiae

AIMS

To provide information on the time-dependent behaviour of microbe staining by fluorescent dyes in the order of seconds, which is important in terms of the recent rapid and online techniques for microbe measurements and/or environmental microbe analysis.

METHODS AND RESULTS

For combinations of yeast (Saccharomyces cerevisiae) and typical dyes, including DAPI (4',6-diamidino-2-phenylindole) and Auramine-O, a suspension of yeast cells in ultrapure water was injected into a dye solution in a micro cuvette placed inside a spectrofluorometer and the fluorescence intensity of the resulting solution was measured at 1 s intervals, starting immediately after the mixing and continued until the time for the maximum intensity using various concentrations of yeast and dyes. The relaxation time τ, which corresponds to ~63·2% of the maximum fluorescence intensity, was shown to decrease to below 1 s with increasing DAPI concentration, whereas it remained constant for 2-3 s with increasing Auramine-O concentration, for example at a yeast concentration of 100 µg ml^-1 .

CONCLUSIONS

For the conditions of yeast >10 µg ml^-1 , DAPI >1 µg ml^-1 and Auramine-O >0·1 µg ml^-1 , τ could be adjusted to below 5 s to achieve a rapid and stable staining.

SIGNIFICANCE AND IMPACT OF THE STUDY

Design and operating conditions for rapid and online measurements of microbes can be optimized.

Identifying organic compounds in exhaled breath aerosol: Non-invasive sampling from respirator surfaces and disposable hospital masks

Exhaled breath aerosol (EBA) is an important non-invasive biological medium for detecting exogenous environmental contaminants and endogenous metabolites present in the pulmonary tract. Currently, EBA is typically captured as a constituent of the mainstream clinical tool referred to as exhaled breath condensate (EBC). This article describes a simpler, completely non-invasive method for collecting EBA directly from different forms of hard-surface plastic respirator masks and disposable hospital paper breathing masks without first collecting EBC. The new EBA methodology bypasses the complex EBC procedures that require specialized collection gear, dry ice or other coolant, in-field sample processing, and refrigerated transport to the laboratory. Herein, mask samples collected from different types of plastic respirators and paper hospital masks worn by volunteers in the laboratory were analyzed using high resolution-liquid chromatography-mass spectrometry (HR-LC-MS) and immunochemistry. The results of immunochemistry analysis revealed that cytokines were collected above background on both plastic respirator surfaces and paper hospital masks, confirming the presence of human biological constituents. Non-targeted HR-LC-MS analyses demonstrated that larger exogenous molecules such as plasticizers, pesticides, and consumer product chemicals as well as endogenous biochemicals, including cytokines and fatty acids were also detected on mask surfaces. These results suggest that mask sampling is a viable technique for EBA collection to assess potential inhalation exposures and endogenous indicators of health state.

Different cardiorespiratory effects of indoor air pollution intervention with ionization air purifier: Findings from a randomized, double-blind crossover study among school children in Beijing

Indoor air pollution is associated with numerous adverse health outcomes. Air purifiers are widely used to reduce indoor air pollutants. Ionization air purifiers are becoming increasingly popular for their low power consumption and noise, yet its health effects remain unclear. This randomized, double-blind crossover study is conducted to explore the cardiorespiratory effects of ionization air purification among 44 children in Beijing. Real or sham purification was performed in classrooms for 5 weekdays. Size-fractionated particulate matter (PM), black carbon (BC), ozone (O₃), and negative air ions (NAI) were monitored, and cardiorespiratory functions were measured. Mixed-effect models were used to establish associations between exposures and health parameters. Real purification significantly decreased PM and BC, e.g. PM_0.5, PM_2.5, PM₁₀ and BC were decreased by 48%, 44%, 34% and 50%, respectively. O₃ levels were unchanged, while NAI was increased from 12 cm^-3 to 12,997 cm^-3. Real purification was associated with a 4.4% increase in forced exhaled volume in 1 s (FEV₁) and a 14.7% decrease in fractional exhaled nitrogen oxide (FeNO). However, heart rate variability (HRV) was altered negatively. Interaction effects of NAI and PM were observed only on HRV, and alterations in HRV were greater with high NAI. Ionization air purifier could bring substantial respiratory benefits, however, the potential negative effects on HRV need further investigation.

Reprint of bioaerosol: A bridge and opportunity for many scientific research fields

Bioaerosol is a concept that is used to describe all biological materials suspended in the air, including bacteria, fungi, viruses, pollen, and their derivatives such as allergens, endotoxin, mycotoxins and etc. In some studies, primary biological aerosol particle (PBAP) is also coined to refer to intact microbes in the air. Bioaerosol is a multidisciplinary research subject, involving many different fields such as microbiology, mechanical engineering, air pollution, medical science, epidemiology, immunological science, biochemistry, physics, nanotechnologies and etc. The bioaerosol field has undergone about 200 years' research history since 1833 when mold spores were first detected in the air by Charles Darwin on the Cape Verde Islands. In recent decades, there has been a research boom in bioaerosol field, thus triggering many outstanding research opportunities. Visible progress has already been made in understanding bioaerosol roles in human health, atmospheric and ecological impacts as well as their respective technologies: bioaerosol capture, monitoring and also inactivation. Most recently, researchers from different fields start to bridge together for solving bioaerosol challenges and addressing key scientific problems, e.g., bioaerosol spread, real-time detection, indoor microbes, human bioaerosol emissions, and bio-defense. Toward this effort, a "Bioaerosol Xiangshan Science Conference-the 600th" has been successfully held in the summer in Beijing, China. A total of 47 scientists and funding agency officials including leading bioaerosol experts from overseas were invited and two-day long extensive discussions on bioaerosol progress and problems were carried out. Future bioaerosol directions have been outlined by the attendees during the conference. Some of the participants have also contributed to this bioaerosol special issue. This special issue consists of a total of 20 bioaerosol articles from eight countries including one review, and contributes to the advances in bioaerosol emission, transmission, health effects, ambient bioaerosols, method development and instrumentation, and control. Through this special issue, the bioaerosol community has obtained a better understanding of bioaerosol health risks and developed the corresponding strategies to confront the threats. This special issue might serve as a starting point to not only link bioaerosol scientists from different continents, but also bring together people from various fields yet with an interest in bioaerosol to collectively advance the field further.