Aerosols Of Bacteria Research Articles

Standoff Laser-Induced Fluorescence Sensors for Biological Warfare Agents

ABSTRACT We report comparison studies of two different sensors, the gated intensified charge-coupled device and the multianode photo multiplier tube detector for standoff detection of bio-aerosol. The ultraviolet laser-induced fluorescence technique is considered. Ultraviolet laser-induced fluorescence signals are evaluated under different bacteria aerosol concentrations, ranges, atmospheric conditions, and solar backgrounds. The signal-to-noise ratio is calculated for both the detectors for daylight and twilight solar conditions. The detectable concentration and range for both of the detectors is evaluated. Standoff ultraviolet laser-induced light detection and ranging is applicable in homeland security for early warning of biological warfare agents.

Minimizing the exposure of airborne pathogens by upper-room ultraviolet germicidal irradiation: an experimental and numerical study.

There has been increasing interest in the use of upper-room ultraviolet germicidal irradiation (UVGI) because of its proven effectiveness in disinfecting airborne pathogens. An improved drift flux mathematical model is developed for optimizing the design of indoor upper-room UVGI systems by predicting the distribution and inactivation of bioaerosols in a ventilation room equipped with a UVGI system. The model takes into account several bacteria removal mechanisms such as convection, turbulent diffusion, deposition and UV inactivation. Before applying the model, the natural die-off rate and susceptibility constants of bioaerosols were measured experimentally. Two bacteria aerosols, Escherichia coli and Serratia marcescens, were tested for this purpose. It was found out that the general decay trend of the bioaerosol concentration predicted by the numerical model agrees well with the experimental measurements. The modelling results agree better with experimental observations for the case when the UVGI inactivation mechanism dominates at the upper-room region than for the case without UVGI. The numerical results also illustrate that the spatial distribution of airborne bacteria was influenced by both air-flow pattern and irradiance distribution. In addition to predicting the local variation of concentration, the model assesses the overall performance of an upper-room UVGI system. This model has great potential for optimizing the design of indoor an upper-room UVGI systems.

Performance of Conventional and Antimicrobial-Treated Filtering Facepiece Respirators Challenged with Biological Aerosols

This study evaluated the filtration performance of four commercially available models of National Institute of Occupational Safety and Health (NIOSH)-certified filtering facepiece respirators (FFR) against both biological and inert aerosols at a flow rate of 85 L/min. Conventional N95 and P100 FFRs and two antimicrobial (AM)-treated FFRs (an N95 and a P95, both with iodine-based AM treatments) were tested for both physical penetration (PENP) and viable penetration (PENV) with three different bioaerosols, including MS2 bacteriophage virus, and the spores and vegetative cells of Bacillus atrophaeus bacteria, in addition to inert sodium chloride (NaCl) aerosol. For each FFR model, the PENP measured with NaCl was predictive of its MS2 PENP, and it was observed that spores and bacteria aerosols were also filtered similarly to the inert aerosol. For both conventional FFRs, up to a 1-log reduction in PENV in comparison with PENP was observed and attributed to the experimental variability of the test system. For both models of AM-FFRs, no statistically significant differences between PENV and PENP for any of the three different bioaerosol challenges were observed. Thus, no bioaerosol filtration enhancement over the conventional FFRs was detected for either iodine-based AM-FFR. In the absence of any standardized test methods, we recommend that future studies evaluating the filtration performance of AM-treated FFRs incorporate the experimental best practices described herein. [Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a pdf file containing I. Review of Research on Antimicrobial-Treated Respirators, and II. Microorganism Propagation, Plating, and Enumeration Protocols.]

Improving the discrimination capability of bioaerosols using a dual-channel ultraviolet aerodynamic particle sizer spectrometer

We report on the results of laboratory evaluation of a dual-channel ultraviolet aerodynamic particle sizer spectrometer for real-time, continues monitoring of bio-aerosols. The detected fluorescence light was divided into two channels, simultaneously measuring the blue (400–500 nm) and green (500–600 nm) signal, which were corresponding to the fluorescence spectra of NAD(P)H and riboflavin, respectively. Primary results show the different fluorescence properties of the bacteria aerosols (Escherichia coli, Staphylococci and Bacillus subtilis var. niger spore) and the substrate (TSA eluate solutions, TSB and Nutrient broth). We demonstrated a promising method to improve the discrimination capability of bioaerosols from non-bioaerosol background components and to distinguish different types of bioaerosol particles.

Feasibility of using real-time optical methods for detecting the presence of viable bacteria aerosols at low concentrations in clean room environments

An experimental investigation was carried out to determine the agreement between two methods of viable bacteria aerosol detection. Various amounts of Bacillus globigii (BG) spores were aerosolized in 1-s bursts into a HEPA-filtered air stream and sampled simultaneously with a fluorescence aerosol particle sensor (FLAPS) and a slit to agar biological air sampler. The slit sampler incorporated 150-mm malt extract culture plates, which were incubated at 37°C for at least 12 h before culturable BG particles were counted in terms of colony-forming units (CFU). A relationship between CFU and optically detected viable bacteria particles was determined as culturable particle concentrations decreased. Through further analytical procedures, the FLAPS showed a limit of detection (LOD) of 4.2 bacterial particle/2.5 l of sampled air or 1.7 × 103 m−3. This real-time bacteria aerosol monitor could be used to detect burst contamination events during a surgical procedure. The technology may be used for developing a dose–response relationship between bacterial particle exposure and infection, a tool potentially helpful in determining patient risk.

Background culturable bacteria aerosol in two large public buildings using HVAC filters as long term, passive, high-volume air samplers

Background culturable bacteria aerosols were collected and identified in two large public buildings located in Minneapolis, Minnesota and Seattle, Washington over a period of 5 months and 3 months, respectively. The installed particulate air filters in the ventilation systems were used as the aerosol sampling devices at each location. Both pre and final filters were collected from four air handing units at each site to determine the influence of location within the building, time of year, geographical location and difference between indoor and outdoor air. Sections of each loaded filter were eluted with 10 ml of phosphate buffered saline (PBS). The resulting solutions were cultured on blood agar plates and incubated for 24 h at 36 degrees C. Various types of growth media were then used for subculturing, followed by categorization using a BioLog MicroStation (Biolog, Hayward, CA, USA) and manual observation. Environmental parameters were gathered near each filter by the embedded on-site environmental monitoring systems to determine the effect of temperature, humidity and air flow. Thirty nine different species of bacteria were identified, 17 found only in Minneapolis and 5 only in Seattle. The hardy spore-forming genus Bacillus was the most commonly identified and showed the highest concentrations. A significant decrease in the number of species and their concentration occurred in the Minneapolis air handling unit supplying 100% outdoor air in winter, however no significant correlations between bacteria concentration and environmental parameters were found.

Evaluation of a new device against bacterial penetration

Objective: This study analyzed how effectively bacteria penetrate through a new filtering device (Muski™) aimed at providing temporary protection against hazardous air contaminants. Materials and methods: A 1.5–7×108 cfu/ml bacterial or spore suspension was aerosolized. Fragments of the Muski filter, previously sterilized by gamma rays, were placed in a sterile stainless steel Seitz filter holder, plugged into an Erlenmeyer vacuum flask connected to a vacuum pump to force the bacteria aerosol through the Muski filter. As a control the same apparatus was used without the Muski filter. To evaluate the bacteria passing through the apparatus, diluent solution was introduced in the Erlenmeyer flask, which was then subjected to mechanical shaking. Both the contents of Erlenmeyer flask and the diluent solution, used to rinse out the Erlenmeyer flask, were filtered through a membrane filtration apparatus. The filtration membrane was transferred to the surface of a Petri dish containing a suitable culture medium f...

A survey of preprocedural antiseptic mouth rinse use in Army dental clinics.

The objective of this project was to evaluate the use of preprocedural mouth rinses in Army dental clinics. Three hundred six-question surveys were distributed to 10 Army dental organizations throughout the United States and Germany during the period from March 2001 to March 2002. Two hundred fifty-four surveys were completed and returned. Simple mathematics were used to evaluate answers to the questionnaires. The 254 respondents included military dentists (n = 190), civilian dentists used by the military (n = 27), registered dental hygienists (n = 20), and military-trained dental hygiene technicians (n = 17). Eighty-four and one-tenth percent of respondents (n = 216) use preprocedural rinses in their practices to prevent possible disease transmission (n = 85) or to decrease chances of postoperative infection (n = 167). Chlorhexidine gluconate (n = 170) and phenol-based essential oil preparations (n = 84) are the most commonly used products. The perceived greatest benefits of preprocedural rinsing are to decrease oral bacterial load (38%), to decrease incidence of postoperative infection (21%), and to decrease aerosolization of bacteria (8.66%). Army dental clinics make extensive use of antimicrobial preprocedural rinses. Chlorhexidine and Listerine (Warner-Lambert Consumer Healthcare, Morris Plains, NJ) are the most commonly used products. Currently available literature appears to support the use of these products in preventing or diminishing the chances of postoperative infection.

Detection of Bioaerosols Using Multiwavelength UV Fluorescence Spectroscopy

This article describes the development of an aerosol generation apparatus to investigate the fluorescence spectra of bioaerosols. The experimental system was set up in a Biosafety Level II Laboratory. The system included an aerosol generator, chamber, aerosol monitoring instrumentation, and laser-induced-fluorescence detection system. The aerosol generators, chamber, and monitors were housed in an enclosure with the exhaust vented through a double HEPA filtration system. A Hospitak nebulizer using aqueous suspensions generated aerosols of bacteria. Aerosols of pollens were generated using a small-scale dry powder generator. The aerosol chamber, with four windows for optical access, was designed with the aid of a computational fluid dynamics code to optimize the generation of aerosol beams with a well-defined geometry for reproducible fluorescence measurements. Aerosol concentrations and aerodynamic diameters in the chamber were determined using a filter, an impinger, a modified Andersen impactor, and an Aerodynamic Particle Sizer. Geometric size and particle shapes were determined using microscopy and imaging analysis. The well-characterized aerosol stream allowed reproducible fluorescence measurements to be made with the aerosol generation methods developed in this work. Fluorescence spectra of four bacteria, Escherichia coli, Staphylococcus aureus , Bacillus subtilis var niger , and Bacillus thuringiensis , were found to be very similar. Calibrations of the fluorescence instrumentation allowed cross sections of live cells, killed cells, and spores to be measured with an uncertainty of about 2 to 5.

33.O.04 Evaluation of protective equipment against biological aerosols in a containement cabinet

Tests of hight efficiency filter with bacteria aerosols.

The quantitative assay of mono-dispersed aerosols of bacteria and bacteriophage by electostatic precipitation.

Three tubular electrostatic precipitators are described for the assay of bacterial and bacteriophage aerosols. Particles can be sampled directly on agar or on agar-impregnated paper in a wide range of aerosol concentrations, or sampled into a fluid for the assay of airborne micro-organisms. Rapid consecutive sampling is possible with the samplers and a collection efficiency approaching 100% is readily obtained. Their sampling efficiency is compared with that of the slit sampler and the liquid impinger.