Collection of Airborne Microorganisms into Liquid by Bubbling through Porous Medium (original) (raw)
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Design and performance of a single-pass bubbling bioaerosol generator
Atmospheric Environment, 2005
We describe and analyze a new particle generator that utilizes a bursting bubble principle and eliminates carrier fluid reuse. In this Liquid Sparging Aerosolizer (LSA), a suspension of particles or microorganisms is pumped at a flow rate of 0.2-2 mL min À1 to the top surface of a porous stainless-steel disk where it forms a thin suspension film. Filtered air is then sparged through the disk into the film causing it to break into bubbles that subsequently burst, releasing particles into the air. The released particles are then captured by the sparging air stream and are carried away. Particles that impinge the glass vessel and liquid droplets not captured by the air stream drain to the bottom of the vessel and play no further role in the aerosolization process. We tested the LSA with disks of different pore sizes (0.2, 0.5, 2.0 and 10.0 mm) and different air flows (2-30 L min À1 ) through the porous disks while generating polydisperse and monodisperse particles. Our tests showed that the use of 0.5 and 2.0 mm porosity disks resulted in the highest output of PSL particles in the desired size range, i.e., comparable to bacterial size. Each pore size seemed to have an optimal air flow rate; the produced aerosol concentration increased with increasing suspension delivery rate. The LSA also demonstrated stability of output concentration when aerosolizing particles over extended periods of time. In addition, the size distribution of injury-sensitive Pseudomonas fluorescens bacteria virtually did not change during 90 min of continuous aerosolization by the LSA. In fact, there was no (0%) viability loss, whereas the bacterial spectrum produced by a Collison nebulizer changed significantly over 90 min and there was a 50% loss in viability. The results indicate that the new instrument could be used to generate particles for the evaluation of pathogen collection methods, inhalation and other studies where extended delivery of stable and undamaged biological aerosols is required. r
Survival of Airborne Microorganisms During Swirling Aerosol Collection
Aerosol Science and Technology, 2000
An earlier study evaluated the physical performance of the Swirling Aerosol Collector, also known as the``BioSampler,'' and found it to have several advantages over the widely used AGI-30 impinger when tested with inert test particles. Th e present study was focused on the physical and biological performance with laboratory-aerosolized microorganisms. The results showed th at the BioSampler has better physical collection ef® ciency for B. subtilis and P.¯uorescens than the AGI-30 wh en water was used as the collection¯uid and the sampling¯ow rate ranged from 8.5 L min I 1 to the standard 12.5 L min I 1 . Additionally, the BioSampler provided equivalent or better microbial recovery for the 2 species than the AGI-30 did. The swirling motion of the collection liquid in the BioSampler generates very few bubbles and therefore causes min imal reentrainmen t of already collected microorganisms. In contrast to the AGI-30, the BioSampler can be used very effectively with nonevaporating liquids, such as mineral oil or glycerol. Min eral oil was found to be a suitable collection¯uid for culture analysis, wh ereas glycerol can be used only for nonculture assays, such as the polymerase chain reaction. By using a more viscous, nonevaporating¯uid, the BioSampler can be used for long-term sampling of low airborne bacterial concentrations, while the AGI-30 impinger, ® lled with a standard evaporating¯uid, can only be used for up to about 30 min.
Evaluation of media for recovery of aerosolized bacteria
Aerobiologia, 1997
Disease transmission by airborne bacteria is well known. Bacterial burden in indoor air is estimated by sampling the air and estimating Colony Forming Units (CFU) using a variety of media. In this study, the recovery of bacteria, after aerosolization in an aerosol chamber, and employing a variety of media, was compared to that achieved using Tryptic Soy Agar medium. The
FEMS Microbiology Letters, 2022
This study examined the water-to-air transfer and viability of the fecal indicator bacteria, enterococci, and compared capture performance of an impactor and aerosol filter. Results show that concentrations of viable enterococci collected by the impactor (70.1 CFU/L) was lower than that using the filter (171.2 CFU/L) at 95% significance. Between the impactor and filter, coefficients of variation equaled 13 and 14%, respectively. Hence, for the collection of aerosolized enterococci in a controlled environment, use of the aerosol filter yielded significantly higher recovery relative to impaction, though equally variable data were collected by both methods. This work confirms that viable enterococci transfer across a simulated air-sea interface and that aerosol filters perform well in capturing viable bacteria. Results from this study are relevant to studies that measure environmentally generated aerosols such as those that occur via wave breaking from sewage contaminated waters.
Evaluation of micro-well collector for capture and analysis of aerosolized Bacillus subtilis spores
PloS one, 2018
Bioaerosol sampling and identification are vital for the assessment and control of airborne pathogens, allergens, and toxins. In-situ analysis of chemical and biological particulate matter can significantly reduce the costs associated with sample preservation, transport, and analysis. The analysis of conventional filters is challenging, due to dilute samples in large collection regions. A low-cost cartridge for collection and analysis of aerosols is developed for use in epidemiological studies and personal exposure assessments. The cartridge collects aerosol samples in a micro-well which reduces particles losses due to the bounce and does not require any coating. The confined particle collection area (dwell~1.4 mm) allows reducing the elution volume for subsequent analysis. The performance of the cartridge is validated in laboratory studies using aerosolized bacterial spores (Bacillus subtilis). Colony forming unit analysis is used for bacterial spore enumeration. Cartridge collecti...
Journal of Aerosol Science, 2011
Experimental bioaerosol generators are widely used in scientific studies. However, the choice of such a generator for a given application is made difficult by the lack of information on the performances or limits of these systems. In this article, we venture the assumption that a bubbling liquid generator constitutes a promising choice to produce experimental bioaerosols with known and controlled characteristics. A generator inspired by the Liquid Sparging Aerosolizer (LSA) developed by was used to aerosolise microorganisms by bubbling compressed air through a bacterial suspension film.
Removal of aerosols by bubbling through porous media submerged in organic liquid
Chemical Engineering Science, 2002
Aerosols can be ÿltered by passing the carrier gas through a ÿbrous ÿlter immersed in water . Bubble ÿltering through porous media. Aerosol Science and Technology, 31, 249 -257. Using water as the irrigating uid signiÿcantly increases the e ciency of ÿltration of particles and adds the possibility for simultaneous removal of alien gases from the carrier. Organic compounds (gaseous and particulate) form a signiÿcant proportion of pollutants in the atmosphere, and e ective puriÿcation is needed for ambient air as well as for cleaning exhaust streams. Water does not have a high level of solubility for gaseous organic compounds, and alternative irrigating liquids need to be considered. Experiments were conducted using sun ower oil as the irrigating uid. The ÿltration e ciencies of the oil are better than for water, for liquid di-ethyl-hexyl-sebacate particles. As the solubility of organic vapours is much higher in oil compared with the one in water, oil provides an excellent opportunity for utilizing as the irrigating liquid for high-e cient simultaneous removal of organic particles and vapours from air carrier. ?
Particuology, 2015
Widely used bioaerosol generators like Collison nebulizer probably produce electrostatically charged particles, but the electrical charges carried by laboratory-generated airborne microorganisms using bubbling aerosolizers are poorly understood. In this study, we measured the fraction of neutral particles and number of elementary charges per particle as a function of the aerodynamic diameter of airborne bacteria (Escherichia coli and Enterococcus hirae). Bioaerosols were produced by a liquid sparging aerosolizer-type bubbling generator, with particle sizes ranging from roughly 0.6 to 2 m. The experimental setup included an electrostatic precipitator and real-time devices including an electrometer, aerodynamic particle sizer, and electrical low-pressure impactor. Experimental results obtained for various operating conditions showed that aerosols produced with a higher bubbling airflow contained a larger proportion of neutral particles (from around 30% to 50%) and that bacteria carried a greater average absolute number of elementary charges (from around-10 to-60 elementary units) than those under lower airflow. Under the investigated conditions, a neutralization step is unnecessary because it may have a negative effect on the viability of sensitive microorganisms. Our results suggest that the neutral fraction can be used downstream of an electrostatic precipitator, and that this setup may have advantages over bipolar neutralizers.
Aerosol Science and Technology, 2011
By sampling aerosolized microorganisms, the efficiency of a bioaerosol sampler can be calculated depending on its ability both to collect microorganisms and to preserve their culturability during a sampling process. However, those culturability losses in the nonsampling processes should not be counted toward the sampling efficiency. Prior to the efficiency assessment, this study was designed to investigate the culturability losses in three non-sampling processes: (1) the tracer uranine induced loss; (2) the loss during aerosolization (pre-sampling process); and (3) the bacteria and uranine recovery in air sample handling procedures for the samples of the Andersen 6-stage impactor and the Airport MD8 (postsampling process). The results indicated that uranine had no significant effect on the culturability of Enterococcus faecalis, Escherichia coli, and Mycoplasma synoviae in suspensions (P > 0.05), but negatively affected the culturability of Campylobacter jejuni (P = 0.01). The culturability of E. faecalis, E. coli, and M. synoviae was not affected by stresses caused by aerosolization (P > 0.05). Only 29% of C. jejuni were still culturable during aerosolization (P = 0.02). In the air sample handling procedures, the four species of bacteria were recovered without significant losses from the samples of the Andersen impactor, but only 33-60% uranine was recovered. E. faecalis, E. coli, and M. synoviae were recovered without significant losses from the samples of the Airport MD8. More C. jejuni was recovered (172%), probably due to multiplication or counting variation.
EC Microbiology, 2018
The study describes the results of a series of comparative experiments aimed at determining the differences in the ability to collect bacteria and fungi colonies by seven different impaction air samplers. The tests were performed simultaneously under identical environmental conditions in a "clean" room routinely used for cell culture or in a biochemistry room generally used for chemical experiments in the microbiological research laboratory of the University of Milan. The air flow in the rooms was switched-off for all the time of the experiments. The seven different air samplers were positioned on a cart, side by side, and operated simultaneously to collect 1m 3 of atmosphere each. The results demonstrated that the numbers of airborne microorganisms impacted on TSA-containing Petri dishes, and grown as single colonies (CFU/m 3), were different for each air sampler, although the difference was not statistically significant. Head to head tests were also performed with two identical TRIO.BAS apparatuses calibrated to 100 or 200 litres of aspirated air per minute. This test aimed at determining if a shorter aspiration time could negatively influence the cell viability and/or the bacterial concentration in the bioaerosol, as determined by counting the number of CFU/m 3. The data ruled out this possibility and suggest that an aspiration time of 200 litres per minute might save time, especially when a repeated air sampling is mandatory for the control of sterility in virology laboratory "clean rooms", pharmaceutical manufacturing areas and surgical rooms in the hospitals.