UV Air, Water & SURFACE Disinfection Technologies
M o l e c u C a r e ®
the world'S MOST POWERFUL ultraviolet IRRADIATION SYSTEMS
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UV Air, Water & SURFACE Disinfection Technologies |
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M o l e c u C a r e ® |
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the world'S MOST POWERFUL ultraviolet IRRADIATION SYSTEMS |
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The Steady-State™ Irradiation Chamber©: Disinfection Ahead of the Curve!™ Aerosol Challenge Test:
MolecuCare Steady-State™
UV Air Disinfection Technology
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Microorganism |
Interest to Test | Kill
Requirement(1) (100%) in UV Microwatt Seconds / cm2 |
| Bacillus subtilis | Bacterial spore, resistant to drying | 11,000 |
| Staphylococcus aureus | Gram positive coccus, 0.8µm diameter; leading cause of nosocomial infection | 6,600 |
| Pseudomonas aeruginosa | Gram negative rod, 0.5-1.0µm wide -x- 3.0-4.0µm long, leading cause of nosocomial infection | 10,500 |
| ØX-174 bacteriophage | virus, 0.025-0.027µm diameter, commonly used in human virus barrier studies | 6,600(2) |
| Aspergillus niger | mold spore, common contaminant, among the most resistant organisms to UV irradiation | 330,000 |
To facilitate the high CFU concentration of the aerosol challenge, a Leap Air Sampler was used to collect a maximum achievable volume of air containing microorganisms and allow for their quantitation. Air volumes passing into the Leap Air Sampler from the Chamber measured up to 336 cubic feet per minute (CFM), and at a velocity to 960 feet per minute (FPM) with the pre-filter in place. Challenge flow and air pressure through the nebulizer were monitored to control mean particle size (MPS), and aerosol MPS was determined using a six-stage viable particle Andersen sampler.
Bacillus subtilis spores (ATCC #9372) were inoculated onto SCDA and incubated at 37o C ± 2o C for 2-5 days. The spores were then harvested with sterile water and a sterile bent glass rod, removing adherent growth. The suspension was filtered through multiple layers of sterile cheese cloth, then heat shocked for 10 minutes at 85o C ± 1C to destroy vegetative cells. The suspension was titrated by serial dilution and plated onto soybean casein digest agar.
S. aureus (ATCC #6538) and P. aeruginosa (ATCC #9027) cultures were inoculated onto approximately 100 mL aliquots of soybean casein digest broth. The broth was then incubated at 37o C ± 2o C for 24 ± 4 hours.
ØX-174 challenge preparation was performed by inoculating approximately 100 mL of nutrient broth with E. coli C (ATCC #13706) and incubating and rapidly shaking the broth overnight at 37o C ± 2o C. A 1/100 culture dilution was prepared and incubated at 37o C ± 2o C. The culture was allowed to grow to a density of approximately 2-4 -x-108 CFU/mL (about 3 hours). Cell density corresponded to an optical density of 0.3-0.6 on a spectrophotometer at 640 nm. The bacterial culture was then inoculated with 5-10 mL of ØX-174 bacteriophage stock (ATCC #13706-B1), and incubated with rapid shaking for approximately 5 hours at 37o C ± 2o C. The virus suspension was centrifuged at 10,000 -x- G for 40 minutes. Host cell debris was then removed by filtering the supernatant through a sterile 0.22 µm filter.
Aspergillus niger (ATCC #16404) was prepared by inoculating a culture onto potato dextrose agar or other appropriate medium and incubating at 20-25o C for 7 days. The culture was harvested by flooding the plates with 0.9% saline with 0.05% polysorbate 80 (Tween). Culture growth was suspended in the saline using a glass rod, and the saline was then filtered through several layers of sterile gauze to remove clumps and debris. The suspension was then vigorously vortexed to further separate clumps.
The Steady-State Irradiation Chamberã was tested in the upright vertical position on integral castors in a laboratory room 9 ft. -x- 12 ft., where a HEPA filtered biological hood collected discharge (exit) air. The Chamberã was modified to occlude its bottom diffusion outlet, and two flexible 8" aluminum discharge ducts were attached to each of two discharge air plenums which exit from either side of the device. One of the ducts was attached to the Leap Air Sampler and the other discharged into a vertical HEPA filtered biological safety cabinet. Both ducts were curved to preserve airflow, and all attachments were sealed with duct tape.
| A thermal anemometer sensor was positioned in the
opening of the Leap Air Sampler and the value recorded. Five different
values were collected across the opening. Air flow velocity exiting the
Chamber© was also measured by
taking readings across the exit duct openings. Air flow readings were
taken at both high and low flow settings, and with and without the
Chamber©'s 150 g/m2 basis
weight pre-filter in place.
The aerosol challenge testing occurred with the Chamber©'s pre-filter in place, though the aerosol nozzle was positioned to bypass the filter and discharge directly into the Chamber© air intake path. Air temperature and relative humidity for both ambient air and air entering and exiting the Chamber© were measured using a temperature probe and an electronic hygrometer, respectively. Approximately 25 mL of the culture suspension being tested (prepared as per above) was placed into a sterile test tube, serving as the challenge reservoir during testing. Sterile silicone tubing was placed into the suspension and seeded to a peristaltic pump. The tubing and nebulizer were purged of air bubbles. The other end of the tubing was connected to a Chicago nebulizer, and the nebulizer was then connected to the inlet pressure source equipped with a pressure gauge. With the Chamber©'s fan operating at low speed, the Leap Air Sampler was turned on, and peptone water was pumped onto the surface of the rotating Sampler collection plate. A vacuum source inside the Sampler drew air directly onto the rotating plate and aerosol particles were impinged onto the peptone water surface. Sampler plate rotation caused the peptone water to migrate to the edge of the plate, where it was continuously drawn off for collection into a sterile bottle. |
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| Pictured above: an early prototype H-10 UV air disinfection unit (positioned horizontally at far right) undergoing extensive high volume airflow testing in a separate series of procedures conducted in the Torrington Research labs in Connecticut. |
The nebulizer was positioned (bypassing the Chamberã's 150 g/m2 filter), UV lights inside the Chamberã were turned on, and challenge aerosol from the nebulizer was directed into the Chamber's® air intake. Nebulizer air pressure was maintained at 5 PSIG and the peristaltic pump was turned on to initiate the aerosol challenge. The Leap Air Sampler collected the effluent air for 10 minutes, after which the pump and Sampler both were turned off, and the assay fluid was collected and titrated using a standard assay procedure.
A control run (zero reset) prior to each test run employed the fan, but not the UV exposure, of the Chamberã, and was conducted under standard test conditions to measure aerosol concentration being delivered to the device. The control ran for 10 minutes and assay fluid was collected and titrated using standard assay procedure.
Mean Particle Size (MPS) was determined during the test
using a six-stage Andersen Sampler, and calculated as follows:
| Stage Number | 1 | 2 | 3 | 4 | 5 | 6 |
| Size of Particles | P1 | P2 | P3 | P4 | P5 | P6 |
| Plate counts | C1 | C2 | C3 | C4 | C5 | C6 |
Where: P1 = 9 µm, P2 = 5.8 µm, P3 = 4.0 µm, P4 = 2.7 µm, P5 = 1.6 µm, P6 = 0.875 µm.
(P1 x C1) + (P2 x C2) + (P3 x C3) + (P4 x C4) + (P5 x
C5) + (P6 x C6)
C1 + C2 + C3 + C4 + C5 + C6
The denominator is equal to a statistically converted stage count. If more than one control set is used, the MPS shall be averaged:
(MPS1 + MPS2 + ... + MPSn) / n
After the Chamberã was allowed to run for 10-20 additional minutes with the UV lamps illuminated, a blank run was performed by turning on the Leap Air Sampler for 10 minutes and collecting the assay fluid (zero reset). The assay fluid was evaluated using standard plate count technique.
Following the blank run the aerosol challenge procedure was again tested with the Chamberã fan setting on high; testing was done exactly as detailed above for the low flow test, for a 10-minute challenge interval. A control run was also performed to evaluate the challenge concentration.
After each test run, 0.1 mL aliquots of the effluent titer of the assay fluid (peptone water) were plated into appropriate agar media and incubated at 37o C ± 2o C for 48 ± 4 hours. Exceptions: the ØX-174 bacteriophage was incubated at 37o C ± 2o C for 18-24 hours, and the A. niger spores were incubated at 20-25o C for up to 7 days. Assay plates were then counted and the log reduction value of the test run calculated using this equation:
| LRV = Log10 |
Total Number
of Organisms in Challenge |
| ORGANISM | LOW AIR FLOW | HIGH AIR FLOW | ||||
| MPS µm | LRV | % REDUCT | MPS µm | LRV | % REDUCT | |
| B. subtilis | 2.3 | 1.3 | 95.2 | 3.0 | 1.2 | 94.3 |
| S. aureus | 3.0 | >4.7 | 99.998 | 3.1 | 1.2 | 94.0 |
| Ps. aeruginosa | UFA(3) | 1.8 | 98.2 | 3.2 | 0.9 | 88 |
| ØX-174 | 2.8 | 3.6 | 99.98 | 2.5 | 1.2 | 93.3 |
| A. niger | 2.8 | 0.9 | 87 | 3.2 | 1.5 | 96.9 |
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Challenge levels used in this study were all greater than 105 CFU per 10-minute test run -- levels difficult to generate free in any room -- and the selected microorganism types were representative of clinical or industrial environments. Since bacterial spores are among the most resistant life forms in nature, Nelson Laboratories concluded that the kill rates of bacterial spores in such brief exposure, in a single pass, in the MolecuCare Steady-State™ Irradiation Chamber© are "significant". The results are encouraging enough to engender interest in the technology from health care providers world wide; devices featuring the Chamberã technology are now in several years of real-world on-site operation in chronic ambient-air contaminant and nosocomial infection environments around the United States. Read the full Nelson Laboratories Inc Report: "Test Results for MolecuCare UV Aerosol Challenge" 1. 1 American Ultraviolet Company, Santa Ana, CA. Applied Ultraviolet Technology, table, "Incident Energies at 253.7 Nanometer Radiation Necessary to Inhibit Colony Formation in 90% of the Organisms and for Complete Destruction", Form No. A-601. 2. 2 Figure reflects UV kill requirement for E. Coli bacteria. 3. 3 Unsuitable for analysis. There were no counts on any of the Andersen sampler plates, thus the MPS could not be measured. U.S. and International Patents, Patent Applications and Patents Pending. |
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| Pictured above; long term beta testing of early mobile prototype H-10 UV air disinfection units in one of several hospitals. |
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© 1997/2012 MolecuCare Inc, New Milford, Connecticut 06776 USA |
