Culturable Bacterial Concentrations Research Articles

Concentrations and Community Structures of Culturable Bacteria in Aerosols of Household Garbage Stations in Shanghai

The airborne microorganism has attracted increasing attention, and household garbage carries various pathogenic bacteria that affect the surrounding environment and public health. In this study, the culturable bacteria in the air were collected by using a six-level Anderson sampler, and the temperature, relative humidity, PM2.5, and PM10 in the garbage stations and their surrounding environment were recorded. The relationships between environmental factors and culturable bacterial pollution in the air were also analyzed. The results showed that the culturable bacterial concentrations in five sampling sites (the garbage station of a villa and the area downwind, the garbage station of a campus, the roof of an office building, and the garbage station of a residential area) were (1254±92), (280±123), (172±47), (84±18), and (175±174) CFU·m-3, respectively. The concentrations of the culturable bacteria in the garbage station of the villa were significantly higher than those of other sampling sites, mainly because there were biochemical treatment facilities for the on-site treatment of wet garbage in the garbage house. The sizes of the culturable bacteria in the garbage station of the villa mainly ranged from 1.1-4.7 μm, and the bacterial sizes at the other four sampling sites were primarily larger than 7 μm, with a few bacteria ranging from 1.1-2.1 μm. In this study, Proteobacteria and Firmicutes were the dominant phyla, and Corynebacterium and Bacillus were the dominant genera. More importantly, some opportunistic pathogens such as Corynebacterium, Staphylococcus, and Acinetobacter were also detected. The concentrations of the culturable bacteria in the garbage station of the villa were highly correlated with temperature, relative humidity, PM2.5, and PM10. Exiguobacterium in the air was highly correlated with PM10, temperature, and relative humidity. The health hazard quotient (HQ) values of the five sampling sites were all less than 1; however, the results of microbial quantitative risk assessment showed that the health risks of the male and female staff in the three garbage houses were all higher than the corresponding reference values. This study revealed the influence of garbage stations on the bioaerosol in the surrounding environment and provided references for the evaluation of air quality in and around garbage stations.

Comparison of airborne bacteria and fungi in different types of buildings in a temperate climate zone city, Kunming, China

The characteristics of airborne bacteria and fungi in different types of buildings are still unclear. This article applied the culturing and next-generation sequencing methods to characterize the airborne bacteria and fungi in five types of buildings during winter in Kunming, China. Results showed that the mean concentrations of fungi in different buildings were similar (approx. 387 ± 388 CFU/m3). The highest culturable bacterial concentration was found in residences, while the lowest was in the library. Lowering relative humidity, PM2.5 concentration and occupant density can reduce the bacterial concentrations. The major bacterial size in residences and in a hospital was 1.1–2.1 μm, while in other buildings was 2.1–3.3 μm. The PM2.5 concentration and occupant activities are key factors that could affect the microorganism size distributions . The community structures of the bacteria in the library and fungi in the hospital showed distinctive differences from the results in other buildings. The community structure of outdoor microorganisms showed great differences between soil and air samples. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and provide valuable data for the formulation of indoor bioaerosol standards in China.

Health risk assessment of airborne bacteria and fungi in different-type buildings in Kunming, a typical temperate Chinese city

The risk assessment of airborne bacteria and fungi between different-type buildings located in temperate climate zone is still unclear. We applied the culturable method to characterize the airborne bacteria and fungi in 10 residences, 1 school, 2 office buildings, 1 hospital, and 1 library during winter in Kunming, China. In a total of 79 rooms, 152 culturable microbial samples were investigated. Results showed that there were significant disparities in bacterial concentrations among various types of buildings. The highest culturable bacterial concentration was found in residences, while the lowest was in the library. In contrast, the fungal concentrations showed little difference. The risk assessment indicated that occupants in different types of buildings in Kunming had an acceptable exposure risk (hazard index < 1) for bioaerosols. The exposure risk for bacteria in residence was significantly higher than in the others, while the mean hazard index of fungi in residence was significantly higher than in schools, hospitals, and libraries. Ventilation could reduce the HI of bioaerosols in rooms. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and highlight the significance of evaluating the microbial concentrations in residence in temperate climate zone in China.

Effect of traffic congestion and vegetation on airborne bacteria in a city of a developing country

The study was designed to determine the variations in the diversity and the total abundance of airborne bacteria in the atmosphere of nine locations in Kandy City, the cultural capital of Sri Lanka. Culturable microorganisms were identified using 16S rDNA sequencing. Quantification of total bacterial abundance was calculated using real-time PCR. Twenty-eight bacterial species were identified by 16S rDNA sequencing. Bacillus cereus, Bacillus pumilus, Pseudomonas aeruginosa, Pseudomonas stutzeri, and Brevundimonas vesicularis were present in all the sampling sites. Most of the recorded species were opportunistic human pathogens of the respiratory tract (Pseudomonas spp., B. cereus, B. vesicularis, Klebsiella pneumoniae), gastro intestine (B. cereus, K. pneumoniae), and skin (B. cereus). The highest total bacterial load (1.42×1010 cells/m2) was at the railway station where traffic congestion was the highest while significantly high mean culturable bacterial concentration (5.35×106 CFU/m2) (p < 0.05) was recorded from the site close to a tea plantation with heavy vegetation cover. This study shows the impact of vegetation and traffic congestion on airborne microorganisms. The presence of opportunistic pathogens highlights the need for risk assessment and management of air quality in congested urban areas.

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.

A portable sensor system for bacterial concentration monitoring in metalworking fluids

Abstract. The detection of bacterial concentrations in metalworking fluids (MWFs), oil-in-water emulsions used in the cutting industries for cooling and lubrication, is important in order to extend the product life-cycle and plan its disposal according to regulations and legislations. The standard method of measuring culturable bacterial concentration is the plate count technique (PCT) that, however, has long response times and is not suitable for automatic implementation outside a laboratory. In this paper a portable sensor system that measures the bacterial concentration in liquid and semi-liquid media exploiting impedance microbiology is presented and tested for the application of MWF microbial monitoring. A set of MWF samples, taken from metalworking plants, have been tested and good agreement has been found between the system response and that of the PCT. The proposed system allows automated bacterial concentration measurements with shorter response times than the PCT (4 to 24 h vs. 24 to 72 h) and is suitable for in-the-field MWF monitoring.

Seasonality in airborne bacterial, fungal, and (1→3)-β-D-glucan concentrations in two indoor laboratory animal rooms

AimsThe purpose of this study was to assess the temporal changes in the concentrations of bioaerosols in a laboratory mouse room (LMR) and laboratory rabbit room (LRR), and to determine...

Characteristics of airborne bacteria in Mumbai urban environment

Components of biological origin constitute small but a significant proportion of the ambient airborne particulate matter (PM). However, their diversity and role in proinflammatory responses of PM are not well understood. The present study characterizes airborne bacterial species diversity in Mumbai City and elucidates the role of bacterial endotoxin in PM induced proinflammatory response in ex vivo. Airborne bacteria and endotoxin samples were collected during April–May 2010 in Mumbai using six stage microbial impactor and biosampler. The culturable bacterial species concentration was measured and factors influencing the composition were identified by principal component analysis (PCA). The biosampler samples were used to stimulate immune cells in whole blood assay. A total of 28 species belonging to 17 genera were identified. Gram positive and spore forming groups of bacteria dominated the airborne culturable bacterial concentration. The study indicated the dominance of spore forming and human or animal flora derived pathogenic/opportunistic bacteria in the ambient air environment. Pathogenic and opportunistic species of bacteria were also present in the samples. TNF-α induction by PM was reduced (35%) by polymyxin B pretreatment and this result was corroborated with the results of blocking endotoxin receptor cluster differentiation (CD14). The study highlights the importance of airborne biological particles and suggests need of further studies on biological characterization of ambient PM.

Are We Biologically Safe with Snow Precipitation? A Case Study in Beijing

In this study, the bacterial and fungal abundances, diversities, conductance levels as well as total organic carbon (TOC) were investigated in the snow samples collected from five different snow occurrences in Beijing between January and March, 2010. The collected snow samples were melted and cultured at three different temperatures (4, 26 and 37°C). The culturable bacterial concentrations were manually counted and the resulting colony forming units (CFUs) at 26°C were further studied using V3 region of 16 S rRNA gene-targeted polymerase chain reaction -denaturing gradient gel electrophoresis (PCR-DGGE). The clone library was constructed after the liquid culturing of snow samples at 26°C. And microscopic method was employed to investigate the fungal diversity in the samples. In addition, outdoor air samples were also collected using mixed cellulose ester (MCE) filters and compared with snow samples with respect to described characteristics. The results revealed that snow samples had bacterial concentrations as much as 16000 CFU/ml for those cultured at 26°C, and the conductance levels ranged from 5.6×10−6 to 2.4×10−5 S. PCR-DGGE, sequencing and microscopic analysis revealed remarkable bacterial and fungal diversity differences between the snow samples and the outdoor air samples. In addition, DGGE banding profiles for the snow samples collected were also shown distinctly different from one another. Absent from the outdoor air, certain human, plant, and insect fungal pathogens were found in the snow samples. By calculation, culturable bacteria accounted for an average of 3.38% (±1.96%) of TOC for the snow samples, and 0.01% for that of outdoor air samples. The results here suggest that snow precipitations are important sources of fungal pathogens and ice nucleators, thus could affect local climate, human health and agriculture security.

Most probable number quantification of hypophosphite and phosphite oxidizing bacteria in natural aquatic and terrestrial environments

Concentrations of hypophosphite and phosphite oxidizing bacteria were found to be high, relative to bacterial concentrations growing on phosphate, in sediment and soil during winter and summer seasons from 12 common terrestrial and aquatic sites using a most probable number method. The percent of total culturable bacterial concentrations that could use these reduced phosphorus compounds as a sole source of phosphorus were as follows: hypophosphite, 7-100%; phosphite, 10-67%; aminoethylphosphonate, 34-270%. The average MPN/g (±SEM) was as follows: phosphate, 6.19×10(6) (±2.40×10(6)); hypophosphite, 2.61×10(6) (±1.35×10(6)) phosphite, 1.91×10(6) (±1.02×10(6)); aminoethylphosphonate, 3.90×10(6) (± 1.95×10(6)). Relatively high concentrations of reduced phosphorus oxidizing bacteria were found in both pristine sites and sites with urban and agricultural disturbance. Concentrations of reduced phosphorus oxidizing bacteria in anoxic sediments and soil were equivalent. Our data indicate that reduced phosphorus oxidizing bacteria are abundant in the environment and provide strong evidence for the importance of bacterial P oxidation in nature.

Impact of Asian dust events on airborne bacterial community assessed by molecular analyses

Abstract Impact of Asian dust events (ADE) on atmospheric bacterial communities was studied using both cultivation and culture-independent methods. In addition, size-segregated aerosol mass concentrations and their chemical compositions were measured and backward trajectory analysis was performed. During the days affected by ADE, culturable bacterial population levels showed significant positive correlations with total suspended particles (TSP) and particulate matter with aerodynamic diameter 10 ), whereas no significant correlation was found during non-Asian dust (NAD) days. Asian dust seemed to directly impact the airborne bacterial communities, as abrupt changes of denaturing gradient gel electrophoresis (DGGE)-band patterns and significant differences in the 16S rDNA clone library between ADE and NAD days were observed. In addition, the changes of DGGE patterns were in agreement with the shift of PM 2.5 chemical composition, suggesting that the outdoor bacterial community was affected by the source and transport pathways of air masses. The isolation sources of clone libraries reflected the sampled air mass transport pathways, which were simulated by backward trajectories. The results of this study revealed that the airborne culturable bacterial concentration was significantly increased and the ambient bacterial community structure was abruptly changed during ADE.