Biohazard Hood to Prevent Infection During Microbiological Procedures

A microbiological hood was designed to reduce the danger of airborne infection of laboratory workers. The hood uses absolute filters to deliver sterile air in a laminar flow to the work area. An air curtain across the hood opening permits easy access but separates the worker from aerosols produced in the hood, and protects material inside the hood from contamination by room air. Tests with bacterial and viral aerosols showed that the air curtain is at least 99.96% effective in preventing airborne particles from entering the work area.     

Mutagenicity of airborne particles from four cities in Taiwan.

The mutagenicity of airborne particles from 8 urban and suburban locations in each of four cities, Taipei, Hsinchu, Taichung, and Kaohsiung, in Taiwan area were investigated with S. typhimurium strain TA98 by Ames Salmonella/microsomal test. The average mutagenic activity of airborne particulate samples from Taipei and Kaohsiung was higher than that from Hsinchu and Taichung with or without metabolic activation. The major direct-acting mutagenic compounds of airborne particulate samples from Taipei and Kaohsiung was similar to that of standard dinitropyrenes mixture (DNPs) in the retention time of HPLC. Moreover, the contents of DNPs of airborne particulate samples from Taipei and automobile exhaust partially purified through Sephadex LH-20 gel filtration and semipreparative HPLC were determined by HPLC. DNPs was major direct-acting mutagens of the urban air samples from Taipei and their major pollutants might be from automobile exhaust. However, the major mutagenic compounds of airborne particulate samples from Hsinchu and Taichung did not correspond to any of the standard compounds tested. The content of benzo[a]pyrene (B[a]P) of airborne particulate samples was also determined by HPLC. The concentration of B[a] P was 0.05-0.62 ng/m3 air sample. The B[a] P contents of airborne particulate samples from four cities in Taiwan did not show good correlation with their mutagenic activity. Thus, we concluded that B[a] P was not a major indirect-acting mutagenic compound in the tested air samples.     

A Monitor for Airborne Bacteria

A unique agar drum sampler is described which indicates, continuously, the number of viable, bacterial particles per unit volume of air at the time and point of sampling. By selection of the timer and the sampling rate the sampler is suitable for quite a wide range of concentration and time. An impaction line of 484 in. greatly increases the capacity of this device over slit samplers and other instruments designed to give time-concentration data for viable airborne particles. This sampler should prove useful for: (i) monitoring airborne bacteria in hospitals, public places, and food and industrial plants; (ii) decay rate studies of bacterial aerosols; (iii) evaluation of aerial germicides; (iv) determination of effectiveness of air conditioning systems in removing airborne bacteria; and (v) many other studies in aerobiology.     

Medical Applications of Dust-free Rooms. III. Use in an Animal Care Laboratory

Bacterial air sampling in an animal care laboratory showed that dense aerosols are generated during cage changing and cage cleaning. Reyniers and Andersen sampling showed that the airborne bacteria numbered 50 to 200 colony-forming units (CFU)/ft³ of air. Of the viable particles collected by Andersen samplers, 78.5% were larger than 5.5 μm. A low velocity laminar air flow system composed of high-efficiency particulate air (HEPA) filters and a ceiling distribution system maintained the number of airborne viable particles at low levels, generally less than 2 CFU/ft³. Vertical air flow of 15 ft/min significantly reduced the rate of airborne infection by a strain of Proteus mirabilis. Other factors shown to influence airborne infection included type of cage utilized, the use of bedding, the distance between cages, and the number of animals per cage.     

Human occupancy as a source of indoor airborne bacteria

Exposure to specific airborne bacteria indoors is linked to infectious and noninfectious adverse health outcomes. However, the sources and origins of bacteria suspended in indoor air are not well understood. This study presents evidence for elevated concentrations of indoor airborne bacteria due to human occupancy, and investigates the sources of these bacteria. Samples were collected in a university classroom while occupied and when vacant. The total particle mass concentration, bacterial genome concentration, and bacterial phylogenetic populations were characterized in indoor, outdoor, and ventilation duct supply air, as well as in the dust of ventilation system filters and in floor dust. Occupancy increased the total aerosol mass and bacterial genome concentration in indoor air PM(10) and PM(2.5) size fractions, with an increase of nearly two orders of magnitude in airborne bacterial genome concentration in PM(10). On a per mass basis, floor dust was enriched in bacterial genomes compared to airborne particles. Quantitative comparisons between bacterial populations in indoor air and potential sources suggest that resuspended floor dust is an important contributor to bacterial aerosol populations during occupancy. Experiments that controlled for resuspension from the floor implies that direct human shedding may also significantly impact the concentration of indoor airborne particles. The high content of bacteria specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust indicates that floors are an important reservoir of human-associated bacteria, and that the direct particle shedding of desquamated skin cells and their subsequent resuspension strongly influenced the airborne bacteria population structure in this human-occupied environment. Inhalation exposure to microbes shed by other current or previous human occupants may occur in communal indoor environments.     

Surveillance of airborne adenovirus and Mycoplasma pneumoniae in a hospital pediatric department

This investigation evaluated the distributions of airborne adenovirus and Mycoplasma pneumoniae in public areas in the pediatric department of Children's Hospital in northern Taiwan. The airborne viral and bacterial concentrations were evaluated twice a week for a year using filter sampling with an airflow rate of 12 liters per minute for eight hours in the pediatric outpatient department and 24 hours in the pediatric emergency room. Real-time polymerase chain reaction assays were conducted for analysis. Approximately 18% of the air samples from the pediatric emergency room were found to contain adenovirus. Approximately forty-six percent of the air samples from the pediatric outpatient department contained Mycoplasma pneumoniae DNA products. High detection rates of airborne adenovirus DNA were obtained in July and August in the pediatric public areas. Airborne Mycoplasma pneumoniae was detected only in July in the pediatric emergency room and the peak levels were found from August to January in the pediatric outpatient department. Airborne particles that contained adenovirus and Mycoplasma pneumoniae were the most prevalent in the pediatric public areas. The potential relationship between these airborne viral/bacterial particles and human infection should be examined further.     

Quantitative sampling of indoor air biomass by signature lipid biomarker analysis

Exposure to airborne biocontaminants may result in a multitude of health effects and is related to a pronounced increase in adult-onset asthma. Established culture-based procedures for quantifying microbial biomass from airborne environments have severe limitations. Assay of the phospholipid fatty acid (PLFA) components of airborne microorganisms provides a quantitative method to define biomass, community composition and nutritional/physiological activity of the microbial community. By collecting airborne particulate matter from a high volume via filtration, we collected sufficient biomass for quantitative PLFA analysis. Comparing high (filtration) and low (impaction) volume air sampling techniques at 26 locations within the Eastern United States, we determined that PLFA analysis provided a viable alternative to the established but flawed culture-based techniques for measuring airborne microbial biomass and community composition. Compared to the PLFA analysis, the culture techniques underestimated the actual viable airborne biomass present by between one to three orders of magnitude. A case study of a manufacturing plant at which there had been complaints regarding the indoor air quality is presented. Phospholipid fatty acid characterization of the biomass enabled contamination point source determination. In comparison with samples taken outdoors, increases in the relative proportion of trans PLFA, reflecting shifts in the physiological status of viable airborne Gram-negative bacteria, were detected in the indoor air samples at a majority of sampling sites. Received 29 September 1998/ Accepted in revised form 8 January 1999     

Size distributions of total airborne particles and bioaerosols in a municipal composting facility

Size distributions of total airborne particles and bioaerosols were measured in a full-scale composting facility, using an optical particle counter and an agar-inserted six-stage impactor, respectively. Higher concentrations of total airborne particles and bioaerosols were detected at a sampling location near the screening process preceded by the composting process than at sampling locations in the composting process. At the sampling location near the screening process, the concentrations of total airborne particles were approximately 10(8)particles/m3 at the size of 0.3 microm and 10(5)particles/m3 at 6.2 microm. The concentration of bioaerosols was about 10(4)CFU/m3 in each stage of 7.0 microm (1st stage), 7.0-4.7 microm (2nd), 4.7-3.3 microm (3rd), 3.3-2.1 microm (4th), 2.1-1.1 microm (5th) and 1.1-0.65 microm (6th). Most of submicron particles smaller than 1 microm among the total airborne particles were believed to originate from the ambient air.     

Collection,particle sizing and detection of airborne viruses

Viruses that affect humans, animals and plants are often dispersed and transmitted through airborne routes of infection. Due to current technological deficiencies, accurate determination of the presence of airborne viruses is challenging. This shortcoming limits our ability to evaluate the actual threat arising from inhalation or other relevant contact with aerosolized viruses. To improve our understanding of the mechanisms of airborne transmission of viruses, air sampling technologies that can detect the presence of aerosolized viruses, effectively collect them and maintain their viability, and determine their distribution in aerosol particles, are needed. The latest developments in sampling and detection methodologies for airborne viruses, their limitations, factors that can affect their performance and current research needs, are discussed in this review. Much more work is needed on the establishment of standard air sampling methods and their performance requirements. Sampling devices that can collect a wide size range of virus-containing aerosols and maintain the viability of the collected viruses are needed. Ideally, the devices would be portable and technology-enabled for on-the-spot detection and rapid identification of the viruses. Broad understanding of the airborne transmission of viruses is of seminal importance for the establishment of better infection control strategies.     

Carcinogenic tryptophan pyrolysis products in airborne particles and rain water

This is the first report that carcinogenic tryptophan pyrolysis products are present in airborne particles and rain water. The airborne particles were collected from August 1988 through October 1988 at 4 locations in Japan. The amounts of 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in the air were 0.23 +/- 0.17 pg/m3 air (mean +/- SD, n = 18) and 0.16 +/- 0.15 pg/m3 air (n = 18), respectively. Moreover, these carcinogens were detected in rain water. These results indicate that Trp-P-1 and Trp-P-2 are ubiquitous environmental components.     

Genotoxic activity of extractable organic matter from urban airborne particles in Shanghai, China

The aim of this research is to investigate the impact of air pollution on the population in Shanghai. The genotoxicity of extractable organic matter (EOM) from the air particles was investigated by the means of the Salmonella plate incorporation assay, rat hepatocyte unscheduled DNA repair assay, and mice micronuclei test. The airborne particles were collected in 13 locations during the summer of 1992 and winter of 1993. The crude extracts were fractionated by acid-base partitioning into acid, base and neutral fractions. The neutral fractions were further fractionated by resin-silica gel column chromatography into three subfractions. The induction of revertants with the crude extracts was higher in winter samples than in summer samples. Both indirect-acting and direct-acting mutagenicity were observed. The mutagenicity was detected with TA98, but was not detected with TA100. The mutagenic activity was the greatest in the acid, aromatic and polar fractions from summer samples. The fractions from the winter samples did not show clear differences. There was no substantial location-related variance in the mutagenic potencies of EOM, but substantial location- or time-related variances in the mutagenic potencies of the airborne particles per cubic meter air were found. While rat hepatocyte unscheduled DNA synthesis (UDS) assay revealed genotoxicity for all the samples, there was no big variance in the genotoxicity of the fractions. The mouse micronuclei test showed results similar to the UDS assay. The difference of locality did not have statistical significance.     

Environmental monitoring in stem cell banks

The processing of stem cell lines for application in human therapy requires a physical environment in which air quality (i.e., the number of airborne particles) is controlled to minimize risk of contamination. The processing facility should be constructed and operated to minimise the introduction, generation and retention of particles and microorganisms. A formal program of environmental monitoring should be maintained in each stem cell bank to specify and assess key factors and their influence on the microbiological quality of the process and product. This program should assure the manipulation of cells involved in the derivation of stem cell lines and their culture under established limits for airborne particles and for microbial contamination of the air and surfaces. Environmental monitoring should also address the regulatory requirements in the countries in which the cells will be used. The monitoring programme will depend on local conditions in each processing centre or cell bank. Each centre will need to evaluate its specific needs and establish appropriate monitoring procedures which should not become intrusive to the extent that they might compromise the quality of the cell banks or products.     

Allergological aerobiology

Summary Aerobiology, in the strict sense, is the science which is studying the transportation of biological particles through the air. This process includes the release, the staying airborne, and deposition of particles of biological origin. Until recently, most of the allergological research has been done on the processes before and after the strict aerobiological pathway. The allergological studies were primarily dealing with the allergenic properties of the particles, irrespective of their aerobiological characteristics. Also, many studies have been done about the effects of allergens in sensitized people, after deposition in the respiratory organs. But for a more complete knowledge of the allergic process, allergological aerobiology in the strict sense is indispensable. The understanding of symptoms of respiratory allergy requires knowledge of the aerodynamic properties of airborne allergen carrying particles.     

Comparison of Microbial Contamination Levels Among Hospital Operating Rooms and Industrial Clean Rooms

Microbial contamination in industrial clean rooms was compared quantitatively and qualitatively with that of hospital operating rooms. The number of aerobic mesophilic microorganisms which accumulated on stainless-steel strips exposed for periods up to 21 weeks to the intramural air of four operating rooms was at least 1 log higher than the accumulation on strips exposed in four clean rooms, and was essentially the same as that found in two factory areas. Volumetric air samplings showed that there were significantly higher numbers of airborne viable particles per cubic foot of air in operating rooms than in industrial clean rooms. In contrast to clean rooms, where most of the airborne contaminants were those associated with human hair, skin, and respiratory tract, the hospital operating rooms showed a very high level of microorganisms associated with dust and soil.     

Indoor sources of mutagenic aerosol particulate matter: smoking, cooking and incense burning

The emission of aerosol particles and their mutagenic activity as well as the emission of some gaseous pollutants has been studied experimentally in order to compare the emission from some indoor pyrolysis processes. Cigarette (tobacco and herbal) smoking, incense and mosquito-coil burning and frying of experimental lean minced pork emitted particulate matter. Their extracts were mutagenic in the Ames Salmonella test with TA98 and activation as well as, with a higher response, in a microsuspension test with the same strain and activation condition. The response of the particles from the smoking and burning processes varied from 3000 to 50,000 revertants per gram of smoked or burnt material in the conventional Salmonella test and from 50,000 to 350,000 revertants per gram in the microsuspension assay. The frying of lean minced pork gave an airborne emission of about 53 and 560 revertants per gram of fried pork, respectively, in the 2 assays. The frying of some common food items following cookbook recipes also emitted mutagenic aerosol particles but the emitted activity was less than that in the pork experiment. Carbon monoxide, isoprene and benzene were present in the emissions from the smoking and burning processes but were not detectable in the frying fumes. The results suggest that incense and mosquito-coil burning can cause indoor air pollution akin to that from cigarette smoking. Indoor air pollution from cooking requires further study.     

Dust and ammonia in horse stalls with different ventilation rates and bedding

Airborne particles and ammonia were monitored in horse stalls managed under four conditions. Two ventilation rates, high (27 air changes per h) and low (5 air changes per h) and two bedding types, paper and straw, were employed. At both ventilation rates, the number of airborne particles generated while the stalls were mucked out was higher with straw than with paper. Particles were more efficiently cleared at the higher ventilation rate in both the straw and paper stalls. Ammonia measurements reflected an accumulation over time. In the stalls with low ventilation, ammonia levels were significantly higher than in those stalls with high ventilation regardless of bedding type. Management decisions and their relationships to respiratory disorders are discussed.     

Bioaerosol mass spectrometry for rapid detection of individual airborne Mycobacterium tuberculosis H37Ra particles

Single-particle laser desorption/ionization time-of-flight mass spectrometry, in the form of bioaerosol mass spectrometry (BAMS), was evaluated as a rapid detector for individual airborne, micron-sized, Mycobacterium tuberculosis H37Ra particles, comprised of a single cell or a small number of clumped cells. The BAMS mass spectral signatures for aerosolized M. tuberculosis H37Ra particles were found to be distinct from M. smegmatis, Bacillus atrophaeus, and B. cereus particles, using a distinct biomarker. This is the first time a potentially unique biomarker was measured in M. tuberculosis H37Ra on a single-cell level. In addition, M. tuberculosis H37Ra and M. smegmatis were aerosolized into a bioaerosol chamber and were sampled and analyzed using BAMS, an aerodynamic particle sizer, a viable Anderson six-stage sampler, and filter cassette samplers that permitted direct counts of cells. In a background-free environment, BAMS was able to sample and detect M. tuberculosis H37Ra at airborne concentrations of >1 M. tuberculosis H37Ra-containing particles/liter of air in 20 min as determined by direct counts of filter cassette-sampled particles, and concentrations of >40 M. tuberculosis H37Ra CFU/liter of air in 1 min as determined by using viable Andersen six-stage samplers. This is a first step toward the development of a rapid, stand-alone airborne M. tuberculosis particle detector for the direct detection of M. tuberculosis bioaerosols generated by an infectious patient. Additional instrumental development is currently under way to make BAMS useful in realistic environmental and respiratory particle backgrounds expected in tuberculosis diagnostic scenarios.     

Dust and ammonia in horse stalls with different ventilation rates and bedding

Airborne particles and ammonia were monitored in horse stalls managed under four conditions. Two ventilation rates, high (27 air changes per h) and low (5 air changes per h) and two bedding types, paper and straw, were employed. At both ventilation rates, the number of airborne particles generated while the stalls were mucked out was higher with straw than with paper. Particles were more efficiently cleared at the higher ventilation rate in both the straw and paper stalls. Ammonia measurements reflected an accumulation over time. In the stalls with low ventilation, ammonia levels were significantly higher than in those stalls with high ventilation regardless of bedding type. Management decisions and their relationships to respiratory disorders are discussed.     

Evaluation of an electrostatic particle ionization technology for decreasing airborne pathogens in pigs

Influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV) and Staphylococcus aureus are important swine pathogens capable of being transmitted via aerosols. The electrostatic particle ionization system (EPI) consists of a conductive line that emits negative ions that charge particles electrically resulting in the settling of airborne particles onto surfaces and potentially decreasing the risk of pathogen dissemination. The objectives of this study were to determine the effect of the EPI system on the quantity and viability of IAV, PRRSV, PEDV and S. aureus in experimentally generated aerosols and in aerosols generated by infected animals. Efficiency at removing airborne particles was evaluated as a function of particle size (ranging from 0.4 to 10 µm), distance from the source of ions (1, 2 and 3 m) and relative air humidity (RH 30 vs. 70 %). Aerosols were sampled with the EPI system “off” and “on.” Removal efficiency was significantly greater for all pathogens when the EPI line was the closest to the source of aerosols. There was a greater reduction for larger particles ranging between 3.3 and 9 µm, which varied by pathogen. Overall airborne pathogen reduction ranged between 0.5 and 1.9 logs. Viable pathogens were detected with the EPI system “on,” but there was a trend to reducing the quantity of viable PRRSV and IAV. There was not a significant effect on the pathogens removal efficiency based on the RH conditions tested. In summary, distance to the source of ions, type of pathogen and particle size influenced the removal efficiency of the EPI system. The reduction in infectious agents in the air by the EPI technology could potentially decrease the microbial exposure for pigs and people in confinement livestock facilities.     

Dispersal of fungal spores from three types of air handling system duct material

Exposure to airborne microorganisms in indoor environments may result in infectious disease or elicit an allergic or irritant response. Air handling system components contaminated by fungi have been implicated in the dispersal of spores into the indoor environment, thereby serving as a route of exposure to occupants. This study was conducted to provide quantitative data on the dispersal of spores from fungal colonies growing on three types of duct material. Galvanized metal, rigid fibrous glass ductboard, and fiberglass duct liner were soiled and contaminated with a known concentration of Penicillium chrysogenum spores. The duct materials were incubated in humidity chambers to provide a matrix of growing, sporulating fungal colonies at a contamination level of 109 colony forming units (CFU) per duct section, consistent for all materials. For each experiment a contaminated duct section was inserted into the air handling system of an experimental room, and the air handling system was operated for three 5-minute cycles with an air flow of 4.2 m3 min–1. The duct air velocity was approximately 2.8 m sec–1. The airborne concentration of culturable P. chrysogenum spores (CFU m–3), total P. chrysogenum spores (spores m–3), and total P. chrysogenum-sized particles (particles m–3) were measured in the room using Andersen single-stage impactor samplers, Burkard slide impactor samplers, and an aerodynamic particle sizer, respectively. The highest airborne concentrations (104 CFU m–3; 105 spores m–3; 104 particles m–3) were measured during the first operating cycle of the air handling system for all duct materials with decreasing airborne concentrations measured during the second and third cycles. There was no significant difference in spore dispersal from the three contaminated duct materials. These data demonstrate the potential exposure for building occupants to high concentrations of spores dispersed from fungal colonies on air handling system duct materials during normal operation of the system.