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.     

Heterogeneity of microbial community structures inside the up-flow biological activated carbon (BAC) filters for the treatment of drinking water

Filtration using biological activated carbon (BAC) performs well in the removal of biodegradable dissolved organic carbon from water sources. The application of ozonation followed by up-flow BAC filtration has gained increasing attention in the world scale. In this study, a pilotscale up-flow BAC filtration system was constructed for the treatment of polluted lake water. The operational results indicated that this BAC filtration system could effectively remove organic matter. Spatial heterogeneity of the microbial community structure inside the BAC filtration system was identified using bacterial 16S rRNA clone library analysis. A marked decrease of microbial diversity in the BAC filtration system was observed along the flow path. Alphaproteobacteria, Gammaproteobacteria and Acidobacteria were found to be the major bacterial groups in the BAC filters. Moreover, Novosphingobium aromaticivorans-like microorganisms were detected. This work might add some new insights towards microbial communities in regards to BAC filtration for the treatment of drinking water.     

Image quality assessment with dose reduction using high kVp and additional filtration for abdominal digital radiography

PurposeDose reduction using additional filters with high kilovoltage peak (kVp) for abdominal digital radiography has received much attention recently. We evaluated image quality with dose reduction in abdominal digital radiography by using high kVp and additional copper filters at a tertiary hospital.MethodsBetween June 2016 and July 2016, 82 patients underwent abdominal digital radiography using 80 kVp in X-ray room 1 and 82 were imaged using 92 kVp with 0.1-mm copper filtration in X-ray room 2. The effective dose was calculated using a PC-based Monte Carlo program. Image quality of the abdominal radiography acquired in the two rooms was evaluated using a five-point ordinal scale, as well as the signal-to-noise and contrast-to-noise ratios.ResultsThe mean effective dose decreased by 25.8% and 25.7% for the supine and standing positions, respectively, when abdominal digital radiography using 92 kVp with 0.1-mm copper filtration was performed. In the 20 patients who performed abdominal digital radiography twice in each room, visual grading scores for visualisation of psoas outlines and kidney outlines are higher in room 1. However, there was no statistical significant difference of visual grading scores among the 124 patients who underwent only one abdominal radiography in the room 1 or 2 (P > 0.05).ConclusionsDose reduction for abdominal digital radiography can be achieved with comparable image quality by performing abdominal digital radiography using 92 kVp with 0.1-mm copper filtration, despite the higher AEC dose.     

Air Quality Monitoring of the Post-Operative Recovery Room and Locations Surrounding Operating Theaters in a Medical Center in Taiwan

To prevent surgical site infection (SSI), the airborne microbial concentration in operating theaters must be reduced. The air quality in operating theaters and nearby areas is also important to healthcare workers. Therefore, this study assessed air quality in the post-operative recovery room, locations surrounding the operating theater area, and operating theaters in a medical center. Temperature, relative humidity (RH), and carbon dioxide (CO₂), suspended particulate matter (PM), and bacterial concentrations were monitored weekly over one year. Measurement results reveal clear differences in air quality in different operating theater areas. The post-operative recovery room had significantly higher CO₂ and bacterial concentrations than other locations. Bacillus spp., Micrococcus spp., and Staphylococcus spp. bacteria often existed in the operating theater area. Furthermore, Acinetobacter spp. was the main pathogen in the post-operative recovery room (18%) and traumatic surgery room (8%). The mixed effect models reveal a strong correlation between number of people in a space and high CO₂ concentration after adjusting for sampling locations. In conclusion, air quality in the post-operative recovery room and operating theaters warrants attention, and merits long-term surveillance to protect both surgical patients and healthcare workers.     

Comparison of aerosol and bioaerosol collection on air filters

Air filters efficiency is usually determined by non-biological test aerosols, such as potassium chloride particles, Arizona dust or di-ethyl-hexyl-sebacate (DEHS) oily liquid. This research was undertaken to asses, if application of non-biological aerosols reflects air filters capacity to collect particles of biological origin. The collection efficiency for non-biological aerosol was tested with the PALAS set and ISO Fine Test Dust. Flow rate during the filtration process was 720 l/h, and particles size ranged 0.246–17.165 μm. The upstream and downstream concentration of the aerosol was measured with a laser particle counter PCS-2010. Tested bioaerosol contained 4 bacterial strains of different shape and size: Micrococcus luteus, Micrococcus varians, Pseudomonas putida and Bacillus subtilis. Number of the biological particles was estimated with a culture-based method. Results obtained with bioaerosol did not confirmed 100% filters efficiency noted for the mineral test dust of the same aerodynamic diameter. Maximum efficiency tested with bacterial cells was 99.8%. Additionally, cells reemission from filters into air was also studied. Bioaerosol contained 3 bacterial strains: Micrococcus varians, Pseudomonas putida and Bacillus subtilis. It was proved that the highest intensity of the reemission process was during the first 5 min. and reached maximum 0.63% of total number of bacteria retained in filters. Spherical cells adhered stronger to the filter fibres than cylindrical ones. It was concluded that non-biological aerosol containing particles of the same shape and surface characteristics (like DEHS spherical particles) can not give representative results for all particles present in the filtered air.     

Degree of bacterial contamination in barbershops using hair dryers in Riyadh

Barbershops provide areas for the growth and transfer of bacterial pathogens and thereby have an impact on public health. Barbershops are ideal places for the interactive spread of infections, including community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Here, the work determines the degree of bacterial contamination of hair dryers used in barbershops. The samples were collected in the city of Riyadh, the Kingdom of Saudi Arabia on March 2019. Significant bacterial contamination was seen, with total bacterial count increasing when the hair dryers were run for 20 instead of 10 s. The study shows a high level of bacterial contamination barbershops using hair dryers, with MRSA being isolated in some. The results suggest that high quality filters should be used inside hair dryers and filters, and theses should be cleaned frequently.     

Diversity of Bacterial Communities that Colonize the Filter Units Used for Controlling Plant Pathogens in Soilless Cultures

In recent years, increasing the level of suppressiveness by the addition of antagonistic bacteria in slow filters has become a promising strategy to control plant pathogens in the recycled solutions used in soilless cultures. However, knowledge about the microflora that colonize the filtering columns is still limited. In order to get information on this issue, the present study was carried out over a 4-year period and includes filters inoculated or not with suppressive bacteria at the start of the filtering process (two or three filters were used each year). After 9 months of filtration, polymerase chain reaction (PCR)–single strand conformation polymorphism analyses point out that, for the same year of experiment, the bacterial communities from control filters were relatively similar but that they were significantly different between the bacteria-amended and control filters. To characterize the changes in bacterial communities within the filters, this microflora was studied by quantitative PCR, community-level physiological profiles, and sequencing 16SrRNA clone libraries (filters used in year 1). Quantitative PCR evidenced a denser bacterial colonization of the P-filter (amended with Pseudomonas putida strains) than control and B-filter (amended with Bacillus cereus strains). Functional analysis focused on the cultivable bacterial communities pointed out that bacteria from the control filter metabolized more carbohydrates than those from the amended filters whose trophic behaviors were more targeted towards carboxylic acids and amino acids. The bacterial communities in P- and B-filters both exhibited significantly more phylotype diversity and markedly distinct phylogenetic compositions than those in the C-filter. Although there were far fewer Proteobacteria in B- and P-filters than in the C-filter (22% and 22% rather than 69% of sequences, respectively), the percentages of Firmicutes was much higher (44% and 55% against 9%, respectively). Many Pseudomonas species were also found in the bacterial communities of the control filter. The persistence of the amended suppressive-bacteria in the filters is discussed with regards to the management of suppressive microflora in soilless culture.     

Efficacy of iodine-treated biocidal filter media against bacterial spore aerosols

Aims: To assess the effectiveness of iodine-treated biocidal filter media against bacterial spore aerosols. Methods and Results: Bacillus subtilis spores were aerosolized and introduced into a filtration system. Both treated and untreated filters exhibited high viable removal efficiency (>99·996%) with negligible variation in pressure drop during the entire experiment. The viability of collected spores on the filter was investigated by enumeration of spores extracted from the filter by vortexing. At room temperature and low relative humidity (RH), the survival fraction of the treated filter was significantly lower than that of the untreated filter (P-value < 0·05). Meanwhile, at room temperature and high RH and at high temperature and high RH, the survival fractions on the treated medium were statistically the same as the untreated control at room temperature and low RH. Conclusions: Both treated and untreated filters achieved excellent viable removal efficiency for spores. The pressure drop of the treated filter was not affected by the iodine treatment. The viability of collected bacterial spores was decreased because of the exertion of iodine disinfectant. Significance and Impact of the Study: The evaluation demonstrates that the iodine-treated filter is a viable medium for respiratory protection against infectious spore aerosols. The results warrant further evaluation of smaller biological agents, which exhibit higher penetration.     

Antimicrobial Air Filters Using Natural Euscaphis japonica Nanoparticles

Controlling bioaerosols has become more important with increasing participation in indoor activities. Treatments using natural-product nanomaterials are a promising technique because of their relatively low toxicity compared to inorganic nanomaterials such as silver nanoparticles or carbon nanotubes. In this study, antimicrobial filters were fabricated from natural Euscaphis japonica nanoparticles, which were produced by nebulizing E. japonica extract. The coated filters were assessed in terms of pressure drop, antimicrobial activity, filtration efficiency, major chemical components, and cytotoxicity. Pressure drop and antimicrobial activity increased as a function of nanoparticle deposition time (590, 855, and 1150 µg/cm2_filter at 3-, 6-, and 9-min depositions, respectively). In filter tests, the antimicrobial efficacy was greater against Staphylococcus epidermidis than Micrococcus luteus; ~61, ~73, and ~82% of M. luteus cells were inactivated on filters that had been coated for 3, 6, and 9 min, respectively, while the corresponding values were ~78, ~88, and ~94% with S. epidermidis. Although statistically significant differences in filtration performance were not observed between samples as a function of deposition time, the average filtration efficacy was slightly higher for S. epidermidis aerosols (~97%) than for M. luteus aerosols (~95%). High-performance liquid chromatography (HPLC) and electrospray ionization-tandem mass spectrometry (ESI/MS) analyses confirmed that the major chemical compounds in the E. japonica extract were 1(ß)-O-galloyl pedunculagin, quercetin-3-O-glucuronide, and kaempferol-3-O-glucoside. In vitro cytotoxicity and disk diffusion tests showed that E. japonica nanoparticles were less toxic and exhibited stronger antimicrobial activity toward some bacterial strains than a reference soluble nickel compound, which is classified as a human carcinogen. This study provides valuable information for the development of a bioaerosol control system that is environmental friendly and suitable for use in indoor environments.     

Significance of Algal Excretory Products for Growth of Epilimnetic Bacteria

Light-stimulated uptake of ¹⁴CO₂ and differential filtration through Nucleopore filters were used to estimate the significance of phytoplankton excretion as a source of bacterial carbon in water samples collected at different seasons of the year in Lake Mendota, Wis. On an annual basis, about 14% of the estimated bacterial production was accounted for by algal excretion, although at certain times of year the fraction of bacterial carbon derived from algal excretion was considerably higher. About 20% of the annual primary production was estimated to pass through the bacterial component.     

Use of Hydrogenophaga pseudoflava Penetration To Quantitatively Assess the Impact of Filtration Parameters for 0.2-Micrometer-Pore-Size Filters

Filters rated as having a 0.2-μm pore size (0.2-μm-rated filters) are used in laboratory and manufacturing settings for diverse applications of bacterial and particle removal from process fluids, analytical test articles, and gasses. Using Hydrogenophaga pseudoflava, a diminutive bacterium with an unusual geometry (i.e., it is very thin), we evaluated passage through 0.2-μm-rated filters and the impact of filtration process parameters and bacterial challenge density. We show that consistent H. pseudoflava passage occurs through 0.2-μm-rated filters. This is in contrast to an absence of significant passage of nutritionally challenged bacteria that are of similar size (i.e., hydrodynamic diameter) but dissimilar geometry.The 0.2-μm-pore-size filter class (0.2-μm-rated filters) includes a large and diverse set of products (22). They include air filters, particle reduction filters, filters used for bioburden reduction, lab-grade filters, and “sterilizing-grade” filters used in sterile-dosage-form manufacture. ASTM F 838-05, the Brevundimonas diminuta challenge test, is a standard for the “sterilizing-grade” filters (4), a subset of the 0.2-μm-rated filters. The “0.2-μm” designation is applied to the larger and more diverse set of products. This designation is based on physical measurements (e.g., the bubble point, the force necessary to extrude air through the capillary network of a wet filter) and mathematical extrapolations (5, 14, 29).The current filter validation approach for parenteral pharmaceuticals involves a demonstration of removal of 7 log₁₀ CFU/cm² of nutritionally starved B. diminuta from bulk drug product liquids (4, 8, 11, 29). B. diminuta can penetrate 0.2-μm-rated filters, but only sporadically and at low levels (12, 21). Larger bacteria (Listeria monocytogenes) have been demonstrated to be able to penetrate 0.2-μm filters after long-term exposure (27). Recently, a species of small waterborne bacteria, Hydrogenophaga pseudoflava, has been shown to penetrate 0.2-μm-rated filters (31-36) to a greater extent than the above-described bacteria. None of these bacteria are actually physically smaller than 0.2 μm, even H. pseudoflava (25, 37, 38).Because H. pseudoflava penetrates 0.2-μm-rated filters in a potentially quantifiable manner, it can be used to study filtration efficiency. In this report, we evaluate the impact of filtration process parameters and bacterial challenge density on passage. We benchmark H. pseudoflava passage against that of nutritionally challenged bacteria which are of similar size (i.e., hydrodynamic diameter) but dissimilar geometry.     

Changes of biomass and bacterial communities in biological activated carbon filters for drinking water treatment

Biological activated carbon (BAC) filtration can usually perform well in removal of biodegradable organic compounds in drinking waters. In this study, a pilot-scale down-flow BAC filtration system was constructed for treatment of ozonated waters. The changes of biomass concentration and bacterial community in the BAC filters with contact time and service time were characterized using phospholipid fatty acid (PLFA) analysis and 16S rRNA gene clone library analysis, respectively. The operational results indicated the BAC filtration system could effectively remove dissolved organic carbon (DOC) and assimilable organic carbon (AOC). Biomass concentration decreased with contact time, but showed only a slight change with service time. Contact time and service time could affect the microbial community structure. Alphaproteobacteria was the largest bacterial group and might have important links with the DOC and AOC removal. This work might provide some new insights into microbial community and biological process in the drinking water biofilters.     

Bacterial community structure of a full-scale biofilter treating pig house exhaust air

Biological air filters represent a promising tool for treating emissions of ammonia and odor from pig facilities. Quantitative fluorescence in situ hybridization (FISH) and 16S rRNA gene sequencing were used to investigate the bacterial community structure and diversity in a full-scale biofilter consisting of two consecutive compartments (front and back filter). The analysis revealed a highly specialized bacterial community of limited diversity, dominated by a few groups of Betaproteobacteria (especially Comamonas) and diverse Bacteroidetes. Actinobacteria, Gammaproteobacteria, and betaproteobacterial ammonia oxidizers (Nitrosomonas eutropha/Nitrosococcus mobilis-lineage) were also quantitatively important. Only a few quantitative differences existed between the two filter compartments at the group level, with a lower relative abundance of Actinobacteria and a higher relative abundance of the Cytophaga-Flavobacteria group in the back filter compared to the front filter. These results confirmed the N. eutropha/Nc. mobilis-lineage as the main ammonia oxidizers in pig house air filters and allowed first hypotheses for the key organisms involved in odor removal.     

Assessment of the bacterial contamination of hand air dryer in washrooms

The present study was carried out, using standard techniques, to identify and count the bacterial contamination of hand air dryers, used in washrooms. Bacteria were isolated from the air flow, outlet nozzle of warm air dryers in fifteen air dryers used in these washrooms. Bacteria were found to be relatively numerous in the air flows. Bacterially contaminated air was found to be emitted whenever a warm air dryer was running, even when not being used for hand drying. Our investigation shows that Staphylococcus haemolyticus, Micrococcus luteus, Pseudomonas alcaligenes, Bacillus cereus and Brevundimonad diminuta/vesicularis were emitted from all of the dryers sampled, with 95% showing evidence of the presence of the potential pathogen S. haemolyticus. It is concluded that hot air dryers can deposit pathogenic bacteria onto the hands and body of users. Bacteria are distributed into the general environment whenever dryers are running and could be inhaled by users and none-users alike. The results provide an evidence base for the development and enhancement of hygienic hand drying practices.     

Rapid Detection of Meat Spoilage by Measuring Volatile Organic Compounds by Using Proton Transfer Reaction Mass Spectrometry

The evolution of the microbial spoilage population for air- and vacuum-packaged meat (beef and pork) stored at 4°C was investigated over 11 days. We monitored the viable counts (mesophilic total aerobic bacteria, Pseudomonas spp., Enterobacteriaceae, lactic acid bacteria, and Enterococcus spp.) by the microbiological standard technique and by measuring the emission of volatile organic compounds (VOCs) with the recently developed proton transfer reaction mass spectrometry system. Storage time, packaging type, and meat type had statistically significant (P < 0.05) effects on the development of the bacterial numbers. The concentrations of many of the measured VOCs, e.g., sulfur compounds, largely increased over the storage time. We also observed a large difference in the emissions between vacuum- and air-packaged meat. We found statistically significant strong correlations (up to 99%) between some of the VOCs and the bacterial contamination. The concentrations of these VOCs increased linearly with the bacterial numbers. This study is a first step toward replacing the time-consuming plate counting by fast headspace air measurements, where the bacterial spoilage can be determined within minutes instead of days.     

Population Size and Distribution of Rhizobium leguminosarum bv. trifolii in Relation to Total Soil Bacteria and Soil Depth

Bacterial cells small enough to pass through 0.4-μm-pore-size filters made up 5 to 9% of the indigenous bacterial population in 0- to 20-cm-depth samples of Abiqua silty clay loam. Within the same soil samples, cells of a similar dimension were stained with fluorescent antibodies specific to each of four antigenically distinct indigenous serogroups of Rhizobium leguminosarum bv. trifolii and made up 22 to 34% of the soil population of the four serogroups. Despite the extensive contribution of small cells to these soil populations, no evidence of their being capable of either growth or nodulation was obtained. The density of soil bacteria which could be cultured ranged between 0.5 and 8.5% of the >0.4-μm direct count regardless of media, season of sampling, or soil depth. In the same soil samples, the viable nodulating populations of biovar trifolii determined by the plant infection soil dilution technique ranged between 1 and 10% of the >0.4-μm direct-immunofluorescence count of biovar trifolii. The <0.4-μm cell populations of both total soil bacteria and biovar trifolii changed abruptly between the 10- to 15-cm and 15- to 20-cm soil depth increments, increasing from 5 to 20% and from 20 to 50%, respectively, of their direct-count totals. The increase in density of the small-cell population corresponded to a significant increase in soil bulk density (1.07 to 1.21 g cm⁻³). The percent contribution of the <0.4-μm direct count to individual serogroup totals increased with soil depth by approximately 2-fold (39 to 87%) for serogroups 17 and 21 and by 12-fold (6 to 75%) for serogroups 6 and 36.     

Formation of bacterial streamers during filtration in microfluidic systems

Bacterial behavior during filtration is complex and is influenced by numerous factors. The aim of this paper is to report on experiments designed to make progress in the understanding of bacterial transfer in filters and membranes. Polydimethylsiloxane (PDMS) microsystems were built to allow direct dynamic observation of bacterial transfer across different microchannel geometries mimicking filtration processes. When filtering Escherichia coli suspensions in such devices, the bacteria accumulated in the downstream zone of the filter forming long streamers undulating in the flow. Confocal microscopy and 3D reconstruction of streamers showed how the streamers are connected to the filter and how they form in the stream. Streamer development was found to be influenced by the flow configuration and the presence of connections or tortuosity between channels. Experiments showed that streamer formation was greatest in a filtration system composed of staggered arrays of squares 10 μm apart.     

Silica Desiccant Packets for Storage and Transport of Streptococcus pneumoniae and Other Clinically Relevant Species

Bacterial isolates are often transported between laboratories for research and diagnostic purposes. Silica desiccant packets (SDPs), which are inexpensive and do not require freezing, were evaluated for storage and recovery of bacterial isolates. Conditions such as inoculum size, swab type and temperature of storage were investigated using ten Streptococcus pneumoniae isolates. The optimized protocol was then tested using 49 additional S. pneumoniae isolates representing 40 serogroups. Overall, S. pneumoniae growth was considered satisfactory (>100 colony forming units) for 98/109 (89.9%) and 20/20 (100%) swabs after 14 days at room temperature or 28 days at 4° C, respectively. Storage in SDPs did not impact on the ability of S. pneumoniae isolates to be subsequently serotyped. When the survival of nine other clinically relevant bacterial species was tested, seven were viable after 28 days at room temperature, the exceptions being Neisseria gonorrhoeae and Haemophilus influenzae. SDPs are suitable for transport and short-term storage of bacterial species including S. pneumoniae.     

Improved Method for Determining Bacterial Filtration Rates in Zooplankton

Filtration rates were determined for a natural population of zooplankton grazers (Bosmina longirostris [Müll.], Cyclops vicinus vicinus [Ulianine], Acanthodiaptomus denticornis [Wierz.], and Daphnia longispina [Müll.]) by using ³H-labeled bacteria as food for these organisms. There was a relationship between filtration rates of the major zooplankton grazers and the prevailing algal and bacterial composition in the lake water. Low filtration rates were obtained in the presence of colonial and filamentous cyanobacteria. The rapid process of bacterial adhesion to the external organs of grazers can result in an overestimation of filtration rates. By using the simple method presented here, filtration rates, with simultaneous correction for bacterial adhesion, can be quickly determined.     

Limax Amoebae in Public Swimming Pools of Albany, Schenectady, and Rensselaer Counties, New York: Their Concentration, Correlations, and Significance

A survey was conducted on 30 halogenated public swimming pools, located in Albany, Schenectady, and Rensselaer counties, to determine their open-water limax amoeba densities. Six were outdoor pools. Other variables measured were the standard plate count, total seston, free residual chlorine or bromine, total alkalinity, total hardness, orthophosphate, total soluble phosphorus, specific conductance, pH, temperature, and several engineering parameters including the rate and type of filtration as well as a saturation index. Amoebae were isolated on agar plates at 37°C using heat-killed bacterial suspensions of Enterobacter cloacae or Escherichia coli. Most probable number estimates of amoebic densities ranged from not detectable (<0.01) to 110 amoebae per liter. The median concentration of amoebae was 0.9/liter. Eighty percent of the pools examined had less than 5 amoebae per liter. Significant correlations (P < 0.05) were found between amoebic densities and the log₁₀ of the standard plate count, orthophosphate, and total soluble phosphorus. No significant difference was found between amoebic densities in outdoor and indoor pools. Preliminary tests for the presence of the human pathogen Naegleria fowleri were inconclusive.