Infection Control Today

FEB 2019

ICT delivers to infection preventionists & their colleagues in the operating room, sterile processing/central sterile, environmental services & materials management, timely & relevant news, trends & information impacting the profession & the industry

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40 ICT January/February 2019 Introduction Surgical site infection (SSI) represents a signifcant source of potentially preventable morbidity and mortality. In the U.S., there are approximately 290,000 incidences of SSI per year, representing an economic loss of $8.36 billion. 1 A signifcant portion of SSIs have been proven to be airborne in origin, particularly deep wound infections. 2 Infection rates in joint replacement surgery have been shown to closely correlate with air bacterial concentrations near the surgical site. 3 Use of ultraviolet light and HEPA air filtration have been employed to reduce air bacterial levels in health care settings. Ultraviolet light, particularly the 270nm C-band wavelength (UVC), is effectively biocidal via DNA inactivation. Recently, a new device, a HEPA-ultraviolet air recirculation system (HUAIRS), has been developed which incorporates a combination of UVC irradiation plus HEPA fltration in a portable unit for placement within the operating room. HEPA and ultraviolet technologies act synergistically: Small pathogens such as viruses tend to be sensitive to UVC and resistant to fltration, while larger organisms such as spore-forming bacteria tend to be resistant to UVC and sensitive to fltration. The HUAIRS device also incorporates technology to prolong exposure and dosage of ultraviolet irradiation within the airstream to maximize inactivation. Objective The objective was to measure, using bacterial microbiology and laser particle measurements, operating theater contami- nation levels to determine whether the use of the HUAIRS system would signifcantly reduce contamination levels in the operating room environment. Materials and Methods The surgical setting was a 36m3 operating room in an outpatient surgical center using conventional, turbulent ventilation. The number of occupants was constant during the control and experimental groups. Sampling was performed on two adjacent days, with the control sampling on the frst day and experimental sampling on the second day. Reconstructive procedures utilizing the same In Practice Reduction of Operating Room Airborne Bacteria with HUAIRS surgeon and techniques were employed in both groups. An air sampling impactor and agar media plates were placed in multiple locations to measure the number of colony forming units (CFU) per cubic meter of bacteria. Measurements in the HUAIRS group were compared to the control group at the same room locations on subsequent days. Results were analyzed using a paired Students T-Test. The HUAIRS device (Aerobiotix, West Carrollton, Ohio) is a novel in-room air disin- fection-recirculation unit. It utilizes a hybrid of biological and physical systems to remove bacteria, fungi and viruses from the air. Its key biocidal technology is a reactor system which provides simultaneous physical fltration and irradiation of high-volume air fow. The reactor system utilizes germicidal c-band ultraviolet light (UVC) focused on a reaction chamber flled with a multitude of clear cylindrical silicate crystals. The silicate crystals function as a solid media flter, slowing and trapping organisms as they pass via the air stream. A unique feature of silicate crystal is that it can be effciently penetrated by UVC irradiation. Therefore, while organisms are slowed or trapped in the solid crystalline matrix, they are inactivated by the penetrating UVC dosage. This increases the inactivation effciency over prior UV technologies. Importantly, the HUAIRS ultraviolet chamber is enclosed and shielded within the device, and does not expose room occupants or materials to ultraviolet irradiation. Further air decontamination is performed by a HEPA flter and preflter to add additional physical filtration and prevent particulate contamination of the reac tor system. Additionally, the HEPA system serves to trap residual particles. For the control group, the HUAIRS device was placed in the room, but was not activated. For the HUAIRS group, the unit was activated and running at a fow rate of 12.7 m3/min. Adherence to all relevant regulations for environmental devices was utilized in the deployment of the HUAIRS device and collection of data. Airborne Particulate Sampling and Analysis Air samples were taken utilizing a real-time particulate monitoring system (Oberon, State College, Penn.). The indoor air quality assessment consisted of measurement of 0.5, 2.5 and 5.0 µM/m3 particulate sizes. A total of 210 particle readings were taken in each of the control group and the HUAIRS group for each of the different particle sizes over a seven hour period. Although particulates represent a mixture of viable and non-viable particles levels, particularly those in the 5 µm range, are considered surrogate measures for bioaerosols, which fall into the same size range. 4 Measurements were taken in a fully occupied general operating room during the procedure while reconstructive procedures were taking place, outside of the sterile feld. The bacteriological analysis was performed independently by EMLab P&K (San Bruno, Calif.) to determine the number of colony forming units (CFU) per m3. Data collected from bacterial CFU counts were analyzed using a paired T-Test. The highest and lowest data point was excluded. Results Air Particulate Sampling The data from airborne par ticulate sampling demonstrated baseline mean levels per sample of 6,889,035; 548,518; 41,886 for 0.5, 2.5 and 5.0 µm particle sizes respectively. In the HUAIRS group, mean particle levels per sample were 2,209,157; 151,508; 14,183. This represented a reduction in particle levels of 68.1%, 72.5%, and 66.3% for 0.5, 2.5 and 5.0 µm particle sizes respectively in the HUAIRS group. Air Bacteriological Sampling The data from airborne bacteriological sampling demonstrated baseline a mean level of 23.8 (range 8-63, SD = 14.8) CFU/m3 in the control group. For the HUAIRS group, the mean levels 11.0 CFU/m3 (range 2-21, SD=4.6). This represented a reduction in CFU levels of 53.8% in the HUAIRS group compared to control (p =.016). Conclusion The HUAIRS device signifcantly decreased the level of airborne bacteria in the operating room. Further studies will demonstrate whether this reduction will translate into a decrease in SSI in surgical patients. By David Kirschman, MD

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