Outdoor Bacteria Research Articles

Impact of outdoor air on indoor airborne microbiome under hazy air pollution: A case study in winter Beijing

Exposure to indoor airborne microbiomes (bioaerosols) is closely associated with human health. However, knowledge regarding the characteristics of indoor bioaerosols in areas affected by serious ambient air pollution is still limited. In this study, indoor bioaerosols were characterized in winter Beijing via quantitative polymerase chain reaction (qPCR) and amplicon sequencing, and compared to outdoor bioaerosols. Concentrations of indoor bioaerosol were significantly lower than those of the adjacent outdoor bioaerosol, and were not significantly affected by outdoor air pollution. Community structures of indoor bioaerosol were distinct from those of outdoor environment, and were differentially affected by ambient air pollution. Specifically, significant change was observed in indoor fungal community impacted by hazy air pollution, while not in bacteria and archaea. Compared to outdoor air, indoor air was preferentially enriched with fungi (~10%) in winter. Besides, about 40% of the bacteria indoors were likely contributed by outdoor bacteria. The results provide useful information regarding the impact of ambient air pollution on indoor bioaerosols, and furtherly highlight the distinction between indoor and outdoor bioaerosol assemblies.

Microbial air contamination with air borne bacteria in the outdoor environment at Janakpurdham, Nepal

Background and Objectives: Bacteria can cause allergic asthma and seasonal allergies, diseases which are increasingly prevalent in developing nations. Allergic asthma is currently affecting millions of people in Nepal. Therefore, the objective of this study was designed to measure the bacterial load in outdoor air.
 Materials and Methods: Airborne outdoor bacteria were assessed during the spring season using conventional methods to investigate the enumeration of airborne microorganisms. This was determined by sampling air using the ‘settle plate technique’. The air samples were collected during the spring season (February-March) from 10 different areas of Janakpur. Counts of airborne bacteria were measured as CFUs collected by gravity onto Nutrients Agar plates. Samples were taken periodically over a period of 2 months of February and March 2017.
 Results: A total of 7,404 bacterial colonies were counted on 30 Petri plates that were exposed for 1 hour. The maximum number of colonies of bacteria was 412. Similarly, the least number of bacterial colonies was 32. Higher numbers of CFUs were found in the petri plates which were exposed for 1 hour in comparison to the petri plates which were exposed for 30 minutes. According to the measurement, 36.6% of total CFUs of bacteria were collected during morning hours, 28.4% during day time and 35% during evening hours. Also, the highest numbers of colonies of bacteria were found in the petri plates that were exposed in ward number 7 and the least number of bacterial colonies were obtained in ward number 9.
 Conclusion: The bacteriological quality of air in janakpur was very poor. Very high microbial load was found in the outdoor air in Janakpur. The microbial count was found higher in morning than the noon and evening.

The abundance of urban endotoxins as measured with an impinger-based sampling strategy

Endotoxins are components of Gram-negative bacteria with inherently high pro-inflammatory potential. In an urban environment, airborne endotoxins may associate with pollutants such as particulate matter, increasing the severity of the immune response by acting as a natural adjuvant to augment inflammatory respiratory disease development. Here, we present a closer look at outdoor urban endotoxins by applying a microbial-targeted collection strategy. Results from 87 samples distributed throughout the city of Antwerp ranged from 0.45 to 93.71 EU/m3, with a geometric mean of 4.49 EU/m3 and 95% confidence interval of 3.53–5.71 EU/m3. Sample collection was also coupled with the use of a Coulter counter, for which the particle count (2.5–10 μm/m3) showed a significant correlation with endotoxin concentration (R2 = 0.24; p < 0.0001; n = 64). In addition, the analysis of the cultivable bacterial colony-forming units on Reasoner’s 2A agar (expressed CFU/m3) showed to be a good indicator for airborne endotoxins (R2 = 0.57; p < 0.0001; n = 58). Moreover, identification of dominant bacterial colonies on these culture plates gave some indications on potential sources of these urban outdoor bacteria and endotoxins.

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

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

Isolation and Molecular Characterization of Klebsiella pneumonia isolated from Dust

"Dust includes many microorganisms such as airborne bacteria. Most types of these bacteria are harmful to humans and causing severe problems. Klebsiella pneumoniae considered as serious nosocomial pathogen that cause pneumonia, UTIs, wound and liver abscesses. One hundred fifty samples isolated randomly from different indoor and outdoor areas during the period November 2014- February 2015. In the indoor isolates bacterium K. pneumoniae was the commonest pathogen (36.70%) followed by S. aureus (22.78%), S. epidermidis (12.65%), Bacillus spp. (10.12%), P. aeruginosa (5.06%), E. cloacae (5.06%), Streptococcus spp.(2.53%), Citrobacter spp.(1.26%) and Pantoea spp.(1.26%). While S. aureus comprises the majority of outdoor bacteria in (41.66%). Using PCR method for detection of Uge gene and followed with direct DNA Sequencing. The multiple sequence alignment (MSA) showed highly conserved area in all studied strains. However, some variants were observed at different positions (24, 124, 152, 163, 165, 185, 199, 200, 207, 209, 248, 279, 284, 291). Also there were changes in a functional whole areas at the studied gene such as (GGCTGG) at the positions (212-217), (ATCCCG) at positions (226-231), (GCCC) at (233-236), (ACCG) at positions (242-245), (GATT) at (263-266), (TCAA) at (269-272). These differences in the gene sequence may indicates special characterizations for the isolated strain."

Bacterial community structures in air conditioners installed in Japanese residential buildings.

The bacterial community structures in four Japanese split-type air conditioners were analyzed using a next-generation sequencer. A variety of bacteria were detected in the air filter of an air conditioner installed on the first floor. In the evaporator of this air conditioner, bacteria belonging to the genus Methylobacterium, or the family of Sphingomonadaceae, were predominantly detected. On the other hand, the majority of bacteria detected in the air filters and evaporators of air conditioners installed on the fifth and twelfth floors belonged to the family Enterobacteriaceae. The source of bacteria belonging to the family Enterobacteriaceae may have been aerosols generated by toilet flushing in the buildings. Our results suggested the possibility that the bacterial contamination in the air conditioners was affected by the floor level on which they were installed. The air conditioner installed on the lower floor, near the ground, may have been contaminated by a variety of outdoor bacteria, whereas the air conditioners installed on floors more distant from the ground may have been less contaminated by outdoor bacteria. However, these suppositions may apply only to the specific split-type air conditioners that we analyzed, because our sample size was small.

Prevalence of Methicillin Resistant Staphylococcal Bioaerosols in and around Residential Houses in an Urban Area in Central India.

Methicillin resistant staphylococci (MRS) commonly found in clinical samples or associated environment pose a major health challenge globally. The carriage rate of MRS in human population is high, especially in India but research on airborne distribution of MRS is scanty. The present study aimed to evaluate the prevalence of MRS in indoor and outdoor environment of residential houses. Air samples were collected using impactor air sampler. The total counts of viable bacteria, staphylococci, and MRS along with the particles of various sizes were determined from indoor and outdoor environment of 14 residential houses. MRS bacteria were identified as methicillin resistant S. aureus (MRSA) or coagulase negative staphylococci (CNS) employing biochemical and PCR assays. The average concentration of MRS inside and outside of the houses was 5.9% and 4.6% of the total bacteria, respectively. The maximum correlation of total indoor and outdoor bacteria with particulate matter was 10 μm (r = 0.74) and 5 μm (r = 0.84), respectively. Statistically, significant positive correlation of staphylococci and MRS was found with particles of 10–25 μm inside the houses. Molecular surveillance, antibiotic stewardship programme, and infection control policies can help to manage increasing MRS burden in developing countries.

Aerobiological study in the Mexico City subway system

Monitoring campaigns in two different seasons were carried out at two underground stations (Tacubaya and Azcapotzalco) of the subway of Mexico City, in order to assess airborne bacterial and fungi concentrations, as well as their relationship with several factors, such as depth of the station, sampling site, temperature, and relative humidity. Sixteen sampling sites were selected according to the depth of the lines and the transit of passengers in the corridors, concourses, and platforms. In addition, samples were also collected in the carriages when they were in movement. Outdoor samples were taken at the two stations for comparison. Two-stage multi-orifice cascade impactors were used to collect aerobiological particles, and with the aid of macroscopic and microscopic characterization were found 57 fungi and 61 bacteria colonies. Outdoor bacteria concentrations ranged from 1 to 68 CFU m−3, while fungi concentrations varied from 6 to 80 CFU m−3. The indoor concentration levels of bacteria and fungi ranged from 1 to 484 CFU m−3 and from 51 to 715 CFU m−3, respectively. Fungi and bacteria indoor concentrations in the subway were higher than outdoor, up to 8 times. Most of bacteria were identified as Gram-positive nonsporulating short bacillus, while the most abundant fungi genera identified were Aspergillus, Penicillium, and Alternaria in that order of frequency. Statistical analysis showed significant differences between the stations and the lines of different depths, showing a greater microorganisms’ concentration with a greater depth. Although bacteria and fungi concentrations were higher in the spring than in winter, this difference was not significant. Even if indoor microbiological pollution in underground stations was higher than outdoor, the concentrations found in this study were lower than indoor air international standards.

Assessment of airborne bacteria and fungi in food courts

A study was undertaken to determine the effect of variations in temperature, relative humidity, occupancy density and location (indoor/outdoor) on the concentrations of viable airborne bacterial and fungal spores at an air-conditioned and a non air-conditioned food stall in Singapore. Typically, bioaerosols consisted of 50.5% bacteria and 49.5% fungi in the indoor environment. In contrast, for the outdoor environment, bacteria on an average only accounted for 20.6% of culturable airborne microorganisms whereas fungal concentrations were 79.4%. Results on bioaerosol size distributions revealed that 67% of indoor bacteria and 68% of outdoor bacteria, 85% of indoor fungi and 68% of outdoor fungi were associated with fine mode particulates (<3.3 μm). Occupant density was the key factor that affected indoor airborne bacteria concentrations while concentrations of outdoor airborne bacteria depended strongly on ambient temperature. Indoor fungal concentration was positively correlated to relative humidity whereas outdoor fungal concentration was positively correlated to relative humidity and negatively correlated to temperature. The study also compared the biological air quality between a non air-conditioned food stall (Stall A) and an air-conditioned food stall (Stall B). The dining area of the former had lower bacterial concentrations as compared to the latter, while fungal spore’s concentrations showed a reverse trend. The dominant airborne bacteria genera were Staphylococcus, Pseudomonas, Alcaligens, and Corynebacterium whereas Penicillium, Aspergillus and Cladosporium were the most common fungal genera and groups in both food stalls.

Assessment of airborne bacteria and fungi in an indoor and outdoor environment

Airborne indoor and outdoor bacteria and fungi were assessed during the spring season using conven- tional methods to investigate the enumeration and identification of airborne micro-organisms. This was determined through air quality sampling using the 'open plate technique'. The air samples were collected during the spring season (March-May) from four different locations. Conventional enumeration of airborne micro-organisms relies on culture- based or microscopic methods. Although a culture-based analysis is most widely used for bio-aerosol, four public places located in urban residential areas were selected for indoor/outdoor air bio-pollutant measurement. The public places included kitchens, classrooms, recreational areas, laboratories. Public parks are an important facility associated with the environmental exposure of children. Cultivation and total microscopic enumeration methods were employed for the sample analysis. 26 groups of bacteria and fungi, either of human or environmental origin were detected. Environmental agents generally predominated while significantly higher counts were detected as the level of hygiene or standard of housing dropped. Seven genera of fungi, mainly members of the genus Aspergillum, were isolated from all residents. Bacteria shows higher growth numbers as opposed to the slow growing fungi. Sample collection and pretreatment, determination techniques and performance results are summarized and discussed.

Use of gelatin filter and BioSampler in detecting airborne H5N1 nucleotides, bacteria and allergens

In this study, the pure influenza A virus (H5N1) nucleotides, dermatophagoides allergens (Der f 1 and Der p 1), and Bacillus subtilis vegetative cells were aerosolized and collected by a Button Aerosol Sampler equipped with gelatin filter and a BioSampler, which were operated at 4 and 12.5 L/min, respectively, for 1–5 min. The collected air samples were analyzed by quantitative polymerase chain reaction (qPCR) and enzyme-linked immuosorbent assay (ELISA). In addition, the performances of the samplers when quantifying total outdoor bacteria were also studied. The cycle threshold (Ct) value for 0.1 fg/μl RNA positive control was observed around 26, and the Ct value for the negative control was about 30. Gelatin filters were shown to report 1-2 times higher nucleotides and B. subtilis concentrations than those obtained by the BioSampler. When sampling outdoor bacteria, both samplers however obtained similar concentration levels ( p-value=0.36). In contrast, the BioSampler reported substantially higher dust mite allergen concentration levels, especially for Der f 1 than the gelatin filters in this study. The sampling time up to 5 min was shown not to have a statistically significant effect on the performance of qPCR when the gelatin filter was used. Such finding was also observed with the performance of ELISA for the sampling time up to 15 min. This study suggests that the bioaerosol sampler, collection medium and analysis methods such as qPCR and ELISA would play overall roles in characterizing airborne biological materials.

Bacteria and Fungi Levels in Various Indoor and Outdoor Environments in Ankara, Turkey

AbstractIn this study, different types of indoor environments (primary school, kindergarten, cafeteria, restaurant, dormitory, dwelling, office, sport salon, library, classroom, and laboratory) and their outdoor environments were investigated in terms of bioaerosol contamination. A total of 120 environments were investigated in Ankara, Turkey. The single‐stage Andersen sampler was used for viable bioaerosol sampling. During the sampling, indoor and outdoor temperature, relative humidity, and CO2 concentration were measured. Total bacteria counts (TBC) and fungi concentrations varied on a large scale within and between the sampling site groups (10–103 CFU/m3). The highest TBC levels were measured in kindergartens, primary schools, restaurants, high schools, and homes, while the highest mold levels were measured in kitchens, bathrooms, and offices. Micrococcus spp., Staphylococcus auricularis, and Bacillus spp. were predominant bacteria species and Penicillium spp., Aspergillus spp., and Cladosporium spp. were the most observed mold genera detected in the samples. Indoor‐to‐outdoor (I/O) ratios of the observed fungi counts were calculated as approximately around 1, and for bacteria counts these ratios were higher than 1. There was no statistical difference between indoor and outdoor mold levels, while a significant difference was found between indoor and outdoor bacteria levels (p &lt; 0.001). A significant correlation between indoor CO2 and bioaerosols indicates insufficient ventilation.

INFERENCE IN DIRICHLET PROCESS MIXED GENERALIZED LINEAR MODELS BY USING MONTE CARLO EM

SummaryGeneralized linear mixed models are widely used for describing overdispersed and correlated data. Such data arise frequently in studies involving clustered and hierarchical designs. A more flexible class of models has been developed here through the Dirichlet process mixture. An additional advantage of using such mixture models is that the observations can be grouped together on the basis of the overdispersion present in the data. This paper proposes a partial empirical Bayes method for estimating all the model parameters by adopting a version of the EM algorithm. An augmented model that helps to implement an efficient Gibbs sampling scheme, under the non‐conjugate Dirichlet process generalized linear model, generates observations from the conditional predictive distribution of unobserved random effects and provides an estimate of the average number of mixing components in the Dirichlet process mixture. A simulation study has been carried out to demonstrate the consistency of the proposed method. The approach is also applied to a study on outdoor bacteria concentration in the air and to data from 14 retrospective lung‐cancer studies.