Airborne Bacteria Research Articles

CORRELATION ANALYSIS BETWEEN INDOOR AIRBORNE BACTERIAL LOAD AND OCCUPANT DENSITY IN HOSPITAL INDOOR AIR

A study of the quantity and types of airborne bacteria and its correlation with human presence was conducted. Air samples were collected from different units for three days and three sessions (morning, afternoon and evening) for the enumeration and identification of bacterial isolates. Walk-through exercise was also conducted prior to every sampling to gather information on the number of occupants present, activities going on, and room characteristics. Isolation study revealed higher bacterial load in the afternoon and evening sessions; with Male Ward and Operating Theatre recording the highest and lowest bacterial loads respectively, as compared to the morning session that was done immediately after cleaning and before influx of people. The Spearman’s Correlation Coefficient showed a positively direct linear correlation between the bacterial load and occupant population irrespective of the three sessions (r = 0.84, 0.88 and 0.93). Identification study showed that the isolates are representatives of normal microflora of the skin, respiratory and gastro-intestinal tracts which includes the following; Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus roseus, Klebsiella pneumoniae, Proteus mirabilis, Bacillus subtilis, Aspergillus, Penicillium, Mucor, Candida and Fusarium species. The study presents evidence of increased concentration of indoor airborne bacteria due to human presence, movement and activities.

Community Structure and Influencing Factors of Airborne Microbial Aerosols over Three Chinese Cities with Contrasting Social-Economic Levels

As an important part of atmospheric aerosol, airborne bacteria have major impacts on human health. However, variations of airborne community structure due to human-induced activities and their possible impact on human health have not been well understood. In this study, we sampled atmospheric microbial aerosols in three Chinese cities (Shanghai, Xiamen, and Zhangzhou) with contrasting social-economic levels and analyzed the bacterial composition using high-throughput sequencing methods. A high similarity of the predominant phyla was observed in three cities but the relative abundances were quite different. At the genus level, the most dominant genus in Shanghai and Xiamen was Deinococcus while the most dominant genus in Zhangzhou was Clostridium. The different characteristics of airborne bacterial in the three cities above may be ascribed to the environmental variables affected by human over-activities such as the vehicle exhausts and coal-burning emissions in Shanghai, the tourist aggregation and construction works in Xiamen, the extensive uses of chemical fertilizers, and agricultural activities in Zhangzhou. The variation of the bacterial community and the pathogenic bacteria detected in three cities would have a potential threat to human health.

Municipal Solid Waste Treatment System Increases Ambient Airborne Bacteria and Antibiotic Resistance Genes.

Landfill and incineration are the primary disposal practices for municipal solid waste (MSW) and have been considered as the critical reservoir of antibiotic resistance genes (ARGs). However, the possible transmission of ARGs from the municipal solid waste treatment system (MSWT system) to ambient air is still unclear. In this study, we collected inside and ambient air samples (PM10 and PM2.5) and potential source samples (leachate and solid waste) in the MSWT system. The results showed that the MSWT system contributed to the increased ambient airborne bacteria and associated ARGs. Forty-one antibiotic-resistant bacteria (ARB) harboring blaTEM-1 were isolated, and the full-length nucleotide sequences of the blaTEM-1 gene (harbored by identical bacillus) from air (downwind samples) were 100% identical with those in the leachate and solid waste, indicating that the MSWT system was the important source of disperse bacteria and associated ARGs in the ambient air. The daily intake (DI) burden level of ARGs via PM inhalation was comparable with that via ingestion of drinking water but lower than the DI level via ingestion of raw vegetables. The antibiotic-resistant opportunistic pathogen Bacillus cereus was isolated from air, with a relatively high DI level of Bacillus via inhalation (104-106 copies/day) in the MSWT system. This study highlights the key pathway of airborne ARGs to human exposure.

Factors Affecting Levels of Airborne Bacteria in Dairy Farms: A Review.

Simple SummaryThe environmental quality of farms plays an important role in the food safety of the dairy industry because it may influence the microbial communities in milk. The microorganisms present in the different areas of a farm have an influence on this environmental quality, using the air as a vehicle of dissemination. However, the ability of this airborne microbial community to contaminate the milk, like the sources of origin of these microorganisms, has not been well studied in dairy farms until now. This review examines the importance of different factors that affect the environmental quality of dairy farms, and must, therefore, be taken into account when considering the importance of environmental microbiology as a tool in the improvement of the quality of milk and dairy products.This review attempts to reflect the importance of different factors that affect the environmental quality of dairy farms and must, therefore, be taken into account when considering the importance of environmental microbiology as a tool in the improvement of the quality of milk and dairy products. The effect of a factor such as temperature is vital for the dairy farm environment, especially when the temperatures are extreme, because a proper choice of temperature range improves the quality of the air and, thus, animal welfare. Similarly, the appropriate level of relative humidity in the environment should be taken into consideration to avoid the proliferation of microorganisms on the farm. Air quality, well-designed livestock housing, proper hygienic practices on the farm, stocking density, and the materials used in the livestock houses are all important factors in the concentration of microorganisms in the environment, promoting better welfare for the animals. In addition, a ventilation system is required to prevent the pollution of the farm environment. It is demonstrated that proper ventilation reduces the microbial load of the environment of dairy farms, enhancing the quality of the air and, therefore, the wellbeing of the animals. All this information is very useful to establish certain standards on dairy farms to improve the quality of the environment and, thereby, achieve better quality milk and dairy products.

Assessment of culturable airborne bacteria of indoor environments in classrooms, dormitories and dining hall at university: a case study in China.

University students’ health may be adversely affected by exposure to indoor bacterial contaminants on their campuses. This study aims (1) to quantify culturable bacterial concentrations in three indoor environments at a university, (2) to investigate the influence of meteorological factors and gender, to assess the relationship between indoor and outdoor, and (3) to estimate the bacterial dose for university students in different indoor environments. Airborne bacteria samples were collected in 12 classrooms, in 12 living rooms and four bathrooms in two dormitory buildings, and in a dining hall. The results showed that the microenvironment in the female dormitory had the highest mean bacterial concentration (2847 CFU/m3), whereas the lowest mean bacterial concentration was observed in classrooms (162 CFU/m3). Indoor bacterial concentrations in male dormitories were significantly lower than in female dormitories probably because of crowding and increased ventilation. Outdoor weather conditions were associated with the indoor concentrations with regard to insufficient ventilation and varying outdoor concentration. The occupants’ activity level was also more closely related to the indoor bacteria concentration in the residential setting. Students experienced about four times higher dose of airborne bacteria in the dormitories than in the classrooms and dining hall.

Human Inhalation Exposure to Aerosol and Health Effect: Aerosol Monitoring and Modelling Regional Deposited Doses.

Since poor air quality affects human health in the short and long term, much research has been performed on indoor and outdoor aerosol exposure; however, there is a lack of specific data on the exposure and health risks of inhalable aerosols that contain bioaerosol in different environments of human life. To investigate the potential exposure to inhalable aerosols (in the monitoring of particulate matter (PM) based on R modeling, variations of PM depend on the ventilation system and bioaerosols based on size distribution) in various environments, the special viability and culturability of bioaerosols and their deposition doses in the respiratory system were evaluated. We conducted exposure assessments on inhalable aerosols in various indoor environments (childcare facilities, schools, commercial buildings, elderly and homes). The fractions of PM (PM10, PM4 and PM2.5) were investigated and, for the bioaerosol, the viability, culturability, inhalation daily dose and the deposited dose of the aerosol in the respiratory system were calculated to evaluate the human health effects. For two years, the distribution of the indoor PM concentration was high in all PM fractions in schools and commercial buildings, and low in the elderly and at homes. For airborne bacteria, the highest concentrations were shown in the childcare facility during the four seasons, while airborne fungi showed high concentrations in the buildings during the spring and summer, which showed significant differences from other investigated environments (between the buildings and elderly and homes: p < 0.05). The viability and culturability for the bioaerosol showed no significant difference in all environments, and the correlation between inhalable PM and bioaerosol obtained from the six-stage impactor showed that the coefficient of determination (R2) between coarse particles (PM10–2.5, the size of stage 2–3) and cultivable airborne bacteria ranged from 0.70 (elderly and homes) to 0.84 (school) during the summer season.

Concentrations of bacteria and bacterial and fungal spores calculated from chemical tracers associated with size-segregated aerosol in a composting plant

The lack of information on biological risks in workplaces arises from the difficulty to measure bioaerosol. This study aimed to develop and improve the bioaerosol monitoring technique that uses proper biomarkers as a tool. Muramic and dipicolinic acids, and ergosterol were used as tracers for bacteria cells, bacterial spores, and fungal spores, respectively. Furthermore, 12- and 13-methyltetradecanoic acids (iso- and anteiso- C15:0) were used to study the presence of airborne bacteria and 3-hydroxy fatty acids were used to determine the concentration of peptidoglycan. Airborne particulate matter was sampled in a municipal indoor waste composting facility by multistage impactor samplers, during three main stages of composting process. The microorganism content, in airborne particles with aerodynamic diameter minor then 1 μm and between 1 and 10 μm, was determined starting from the aforementioned biomarker concentrations. For iso- and anteiso- C15:0, a conversion factor to transform its concentration into bacterial content was tentatively proposed. The results show that the chemical method covers some gaps in the information about bioaerosol presence in polluted atmospheres. Differences up to two orders of magnitude are observed, by comparing the results obtained by biomarkers and by cultivation-dependent methods. The microbial content, expressed as a percentage by mass on respect the PM, ranged from 4 to 28% with higher percentages during shredding and mixing stages and lower values during biocell opening operations. Bacterial spores, bacterial cells, and fungal spores detected were high in number, compared with the findings in similar studies elsewhere.

Bacterial Diversity and Community Structure Antibiotic-resistant Bacteria in Bioaerosol of Animal Farms

Confined animal feeding operations generate high concentrations of airborne antibiotic-resistant bacteria, including pathogenic strains that may pose a health risk to both animals and farm workers and pollute the local air environment. In this study, tetracycline and erythromycin-resistant bacteria were used as examples to study the biodiversity and community structure of airborne antibiotic-resistant bacteria in animal farms. The Anderson sampler was used to collect bioaerosols samples from the inside environment and outside atmospheric environments. A comparative analysis of biological differences of antibiotic-resistant bacteria was conducted on fine and coarse particles, bioaerosol samples inside the house, fecal samples, and inside and outside bioaerosol samples based on the result of the Illumina MiSeq sequencing. The key genus that drives the above differences was also studied. Results showed that the biodiversity of airborne erythromycin-resistant bacteria was higher than that of airborne tetracycline-resistant bacteria, and the biodiversity of bioaerosol samples in the house was higher than that in fecal samples. There were no significant differences in the biodiversity and community structure of airborne antibiotic-resistant bacteria between fine and coarse particles. Actinobacteria is one of the key bacteria responsible for the differences between erythromycin-resistant bacteria and other bacterial populations. Staphylococcus is one of the key genera of tetracycline-resistant flora that is distinguished from erythromycin resistance and all bacterial flora. The results of the community structure showed that there was no significant difference in the dominant flora and the community structure of tetracycline and erythromycin-resistant bacteria. The community structure of feces and bioaerosol samples is different at the genus level, and the dominant bacteria are likewise different. The results of this study provide basic data for the accurate assessment of the current status of antibiotic-resistant bacteria in animal farms and their ecological risks.

Investigation of indoor air quality in the ventilated ice rink arena

The indoor air quality (IAQ) of an ice rink, located in the Upper Silesia Region of Southern Poland, was assessed during the winter holidays. Ice rinks are characterized by unusual conditions and multiple sources of pollution. This study evaluated the relative importance of the ventilation system (VS) for maintaining the indoor microenvironment in the ice rink. A preliminary investigation of the concentration levels and characteristics of the indoor and outdoor bacterial aerosol was conducted. Bacterial concentration levels were obtained using a six-stage Andersen cascade impactor. Bioaerosol particles, captured on nutrient media on Petri dishes, were quantitatively evaluated and qualitatively identified using a GEN III Biolog system. Concentration levels of airborne bacteria were above 103 CFU/m³, both when the VS system was turned off (990 CFU/m3) and when it was operational (740 CFU/m3). Results show that the mean concentration of bacteria aerosol was lower when the VS was active. There was a dominance of Gram-positive cocci identified in the indoor environment, which indicates that most of the bacteria present in the studied building were relatively fresh and mostly of human-origin. These data were used to estimate the ice rink exposure dose (IRED) of bioaerosols for building personnel and for children. The highest value of IRED over the study period was obtained for children (220 CFU kg−1).

Airborne Decontamination of an Intensive Care Isolation Room using 405 nm Antimicrobial Light Technology

Lighting systems which incorporate antimicrobial 405nm light have been developed for safe continuous, environmental decontamination, with previous studies demonstrating efficacy for decontamination of frequently-touched surfaces around clinical areas. This study provides first direct evidence of the effects of this decontamination system for control of airborne contamination. The study was conducted in a patient-occupied ICU isolation room over a 15-day period, with air samples collected at set times (before, during and after daily use of the decontamination system). Samples were also collected in the empty room prior to occupation. Environmental monitoring occurred every second day using a sieve-impactor sampler (500L air samples collected every 10-min over 2-hr (n=13)). Room activity was logged and bacterial contamination levels recorded as cfu/m3of air. After 2-day use of the system, airborne contamination significantly decreased from a mean of 905.2 cfu/m3 to 48.8 cfu/m3 (P=0.002). Levels then remained fairly consistent over the remaining period of system use (48.8-189.8 cfu/m3) before significantly rising after the system was turned off for 3-days (P=0.001). Additional samples collected in isolation rooms without the decontamination system demonstrate that the levels of airborne bioburden tend to increase upon increasing patient stay, however low levels were maintained as patient occupation increased when the system was in use. This study provides first direct evidence of the susceptibility of airborne bacteria to 405nm light within a clinical setting. This patient-safe technology has the potential to improve infection control strategies by complementing existing measures, which could reduce the number of infections arising from environmental sources.

Disinfection by in-duct ultraviolet lamps under different environmental conditions in turbulent airflows.

In this study, we investigated the effects of environmental factors such as airflow velocity, relative humidity (RH), temperature, and duct reflectance on the performance of in-duct UVC lamps. Staphylococcus epidermidis, Pseudomonas alcaligenes, and Escherichia coli were used as the test bacteria. The UV irradiance, disinfection efficacy, and UV susceptibility constant (Z value) of the test bacteria were experimentally determined. The results showed that the UV disinfection efficacy decreased as the airflow velocity and RH increased. The maximum UV disinfection efficacy was obtained at temperature of 20-21°C compared with the performance at lower temperature (15-16°C) and higher temperature (25-26°C). When the RH increased from 50% to 90%, the Z values of airborne bacteria reduced by 40%, 60%, and 38% for S epidermidis, P alcaligenes, and E coli, respectively. Besides, susceptibility constants had lower values under both cooling temperature (15-16°C) and heating temperature (25-26°C) compared with that under the temperature of 20-21°C. It was observed that S epidermidis generally had the highest resistance to the UV irradiance. The results also showed that the UV disinfection efficacy was lower in the duct with a black surface than in the clean duct.

LIVE/DEAD BacLight染色による浮遊細菌の濃度と生存率の測定

LIVE/DEAD BacLight染色による浮遊細菌の濃度と生存率の測定

Indoor exposure to airborne bacteria and fungi in sensitive wards of an academic pediatric hospital

Airborne bacteria and fungi in hospital environments are of great concern due to their potential role as a source of nosocomial infections. The aim of this study was to evaluate concentration and diversity of airborne bacteria and fungi in relation to particle mass concentration in sensitive wards of a pediatric hospital. The study was performed in the cardiac care unit (CCU), the neonatal intensive care unit (NICU), the cancer blood ward (BW), the ENT (ear, nose, throat) operation room (OT1) and the eye operation room (OT2). The air samples were collected by impaction using the single-stage Andersen sampler. The flow rate and sampling time of the pump were adjusted to 28.3 l/min for 5 min. The mean concentration of indoor airborne fungi and bacteria ranged from 0–63 to 19–356 CFU/m3, respectively. OT2 and CCU wards were the most contaminated wards for airborne bacteria and fungi, respectively (243 ± 77 vs. 30 ± 7 CFU/m3). The airborne Gram-positive cocci (Staphylococcus and Micrococcus) were the most detected bacterial genera (75%) in all indoor air samples, and the most prevalent genera in indoor environment were Cladosporium spp. (19%) followed by Penicillium spp. (16%), Aspergillus spp. (16%) and Paecilomyces spp. (10%). Results showed that the outdoor airborne bacteria and PM concentration at different sizes were significantly higher than indoors, suggesting that the indoor airborne particle may have originated from the outdoor air. There were significant positive relationships between indoor airborne fungi concentrations with indoor PM2.5 and PM10.

A valuable experimental setup to model exposure to Legionella’s aerosols generated by shower-like systems

The mechanism underlying Legionella aerosolization and entry into the respiratory tract remains poorly documented. In previous studies, we characterized the aerodynamic behaviour of Legionella aerosols and assessed their regional deposition within the respiratory tract using a human-like anatomical model. The aim of this study was to assess whether this experimental setup could mimic the exposure to bioaerosols generated by showers. To achieve this objective we performed experiments to measure the mass median aerodynamic diameter (MMAD) as well as the emitted dose and the physiological state of the airborne bacteria generated by a shower and two nebulizers (vibrating-mesh and jet nebulizers). The MMADs of the dispersed bioaerosols were characterized using a 12-stage cascade low-pressure impactor. The amount of dispersed airborne bacteria from a shower was quantified using a Coriolis® Delta air sampler and compared to the airborne bacteria reaching the thoracic region in the experimental setup. The physiological state and concentration of airborne Legionella were assessed by qPCR for total cells, culture for viable and cultivable Legionella (VC), and flow cytometry for viable but non-cultivable Legionella (VBNC). In summary, the experimental setup developed appears to mimic the bioaerosol emission of a shower in terms of aerodynamic size distribution. Compared to the specific case of a shower used as a reference in this study, the experimental setup developed underestimates by 2 times (when the jet nebulizer is used) or overestimates by 43 times (when the vibrating-mesh nebulizer is used) the total emitted dose of airborne bacteria. To our knowledge, this report is the first showing that an experimental model mimics so closely an exposure to Legionella aerosols produced by showers to assess human lung deposition and infection in well-controlled and safe conditions.

Conflicting effects of a portable ultra-clean airflow unit on the sterility of operating rooms: A numerical investigation

The onset of post-operatory surgical-site infections is significantly correlated with the concentration of viable airborne bacteria that are shed from the surgical team or entering the operating room during door openings and are deposited directly on the patient's wound or on surgical instruments.The ultra-clean vertical laminar airflow ventilation system is often used to protect the main surgical area of operating rooms. The clean zone provided by the laminar airflow system is crowded with staff and furniture. As a result, some surgical instruments might remain outside the protected area. We use a numerical simulation to investigate the capability of a portable ultra-clean airflow unit to reduce the contamination of the principal instrumentation table by airborne bacteria, during a sham operation. The numerical model is thoroughly validated against the experimental data available for a test room. The portable air-cleaning device maintains sterile conditions on the principal instrumentation table over a range of flow rates of the general ventilation, although it induces higher levels of bacterial contamination in other zones of the room at the same time.

Simplified methods of monitoring airborne bacteria for quality and environmental management in the Japanese food industry

Airborne microbes are examined generally by sampling them on culture media and counting the number of their colonies formed. However, because it takes at least two days for bacteria and five days for fungi to be cultivated, reliable data may not be obtained in a time of need. Therefore, the development of simple and quick detection methods is required. In this study, rapid detection methods of indoor airborne bacteria for the improvement of quality and environmental management were reviewed, and a basic study on simplified monitoring techniques of airborne bacteria applicable to food factories was carried out.

Distribution of total bacteria and staphylococci in PM2.5, PM10 and total dust in the emission of two fattening pig houses/Verteilung von Gesamtbakterien und Staphylokokken in PM2,5, PM10 und Gesamtstaub in der Emission von zwei Mastschweineställen

The particle size distribution of airborne bacterial conglomerates is an important factor in calculating possible spread distances of the bacteria over the air. Therefore, a size-selective collection system based on an emission impinger was developed to compare the distribution of total bacteria and staphylococci in particle fractions PM2.5, PM10 and total dust in the emission of two fattening pig stables. Mean emissions of 7.2 × 104 cfu/m³ total bacteria, 6.1 × 104 cfu/m³ staphylococci and 2.8 × 106 cells/m3 measured. About 30% of total bacteria and staphylococci were found in the PM2.5 particle size fraction and about 60% in PM10. The average dust distribution was 80% PM10 and 60% PM2.5. The results show that airborne bacteria from fattening pig units mainly occur on larger particles and do not correlate with dust fractions. The found conditions should be considered in future dispersion modelling.

Quality of Airborne Bacteria in Operating Theaters in Several Hospitals in Jakarta and Its Surrounding Areas in 2018-2019

Nosocomial infection is an infection obtained by a patient or hospital staff while in hospital. This infectionplays a role in causing morbidity and mortality in hospitals and can occur in various hospitals rooms, includingoperating theaters. Nosocomial infections can occur due to various factors, one of which is contamination fromairborne bacteria. In some countries, regulations are set to limit the concentration of airborne bacteria, both in theoperating theaters and other rooms in hospitals, hence the need for monitoring and supervision of air quality asareflection on the cleanliness conditions in hospitals. Based on this, it is necessary to know the bacteriological airquality in the operating theaters in several hospitals in Jakarta and surrounding areas as one of the steps to preventnosocomial infections. The method uses an air sampler with the principle of impaction. Air sampler works byseparating the particles from the air by utilizing the inertia of the particles to force the bacteria to settle to thesurface of the medium. A total of 217 examinations in the operating theaters were carried out in 17 hospitals inJakarta and surrounding areas during January 2018 to June 2019. The majority of the operating theaters inhospitals in Jakarta and surrounding areas have air quality that met appropriate quality standards. In 2018, 120 of137 (87.59%) examination in the operating theaters met the quality standar. Meanwhile in 2019, 70 of 80(87.50%) operating theaters met the standard determined by the Ministry of Health of the Republic of Indonesia. Key words: air sampler method, operating theater, quality of air bacteria

Klarite as a label-free SERS-based assay: a promising approach for atmospheric bioaerosol detection.

Detecting atmospheric bioaerosols in a quantitative way is highly desirable for public health and safety. This work demonstrates that surface-enhanced Raman spectroscopy (SERS) is a simple and rapid analytical technique for the detection of atmospheric bioaerosols, on a Klarite substrate. For both simulated and ambient bioaerosols, this detection assay results in an increase in the enhancement factor of the Raman signal. We report a strong SERS signal generated by bioaerosols containing living Escherichia coli deposited on Klarite. Furthermore, we demonstrate that SERS mapping can be used to estimate the percentage of airborne, living Escherichia coli. Moreover, Klarite provides differently distinct SERS spectra at different bacterial growth phases, indicating its potential to identify changes occurring in the bacterial envelope. Finally, we applied SERS for the rapid detection of Escherichia coli in ambient bioaerosols without using time-consuming and laborious culture processes. Our results represent rapid, culture-free and label-free detection of airborne bacteria in the real-world environment.

Detection of airborne bacteria from patient spaces in tuberculosis hospital.

The spread of nosocomial bacterial infection greatly threatens public health and the impact of nosocomial infection worsens if highly pathogenic bacteria, Mycobacterium tuberculosis as an instance, involves. In this study, we have investigated the presence of airborne M. tuberculosis in a specialized tuberculosis hospital. The study sites selected were waiting room I, II, and ward VI patient lounge, Masan National Tuberculosis Hospital, where the modern ventilation system is on the operation for opportunistic infection prevention. The air samples were collected from the different sites three times for 1 day, and after air collection, air sampled disposable filter membrane was incubated for 4 weeks on nine Middlebrook 7H11 agar plates. Our data showed that out of nine incubated 7H11 plate agars, four plates showed bacterial growth and these grown bacterial colonies were isolated and identified. Among bacterial species identified, there was a colony of Mycobacterium mageritense, one of nontuberculous Mycobacteria. Although there was no M. tuberculosis, the cause of tuberculous disease and transmitted through the nosocomial infection, all pathogens detected were known to be associated with nosocomial infection. Hospitals dealing with infectious diseases should always be wary that ventilation system does not guarantee safety from airborne pathogen exposure hence should continuously monitor the presence of other hospital-associated infection causing pathogenic microorganisms.