Xenon lamps produce pulsed flashes of germicidal UV light at wavelengths from 200-315 nm, killing microbes on environmental surfaces.
Ultraviolet (UV) light can destroy pathogenic bacteria, including Clostridioides difficile spores, but measuring the effectiveness of UV can be tricky, as investigators with Penn State Health, Milton S. Hershey Medical Center, found out. Their recent study in the American Journal of Infection Control1describes the impact of portable pulsed-xenon UV disinfecting devices in 6 units of their hospital that had registered high C. diff infection (CDI) rates. The C. diff rates were measured over a 9-month period before and a 9-month period after the devices were installed, with no difference in C. diff contamination.
“Appropriate terminal cleaning evaluated by fluorescent marking environmental auditing did not significantly change over phase 1 and 2 study periods with an average of 87% of 6510 tested high-touch surfaces demonstrating adequate removal of fluorescent marker,” the study states. “Use of UV devices during the 9-month phase 2 study period in 2017 averaged 93.6% of 8298 targeted terminal discharges without notable differences in use between units.”
The rate of healthcare-associated C. diff infection (HA-CDI) per 1000 patient-days for the units during phase 1 was 1.57 of 1000 patient-days compared with 1.61 of 1000 patient-days during the phase 2 study for the same hospital units.
Fibi Attia, MD, MPH, CIC, the study’s corresponding author and a member of Infection Control Today®’s Editorial Advisory Board, tells ICT® that although the findings didn’t necessarily surprise her, they did cause her to re-examine how best to use UV disinfection.
“Although we were optimistic that UV disinfecting devices would reduce the burden of pathogens in the environment, we always try to evaluate our techniques and processes,” Attia says. “When we didn’t see any impact on our infection data, we studied it in more depth. We also know that there are many factors that contribute to C. difficile infection rates. Even if microbe burden is decreased on surfaces that can be treated with UV, this in itself may not be sufficient to cut down C. difficile infection rates.”
Phase 1 of the study (when portable pulsed-xenon UV disinfecting devices were not used) occurred from January 2016 through September 2016. The devices were installed from October 2016 to December 2016, with full implementation by January 2017, which was when the 9-month phase 2 period of the study started. “Compliance reports for UV device utilization were generated automatically each time the device was used,” the study states.
Terminal cleaning focuses on infection spread and can vary from hospital to hospital, but often involves cleaning walls and floors, and removing all detachable objects and disinfecting them before they are returned to the room. It is usually conducted by environmental services (EVS).
The hospital rooms in the study were cleaned with a sporicidal disinfectant cleaning product: sodium hypochlorite in 2016, acid/hydrogen peroxide-based sporicidal in 2017. Randomly selected rooms were then subjected to fluorescent tagging to see how well they’d been cleaned.
The diagnosis of HA-CDI was based on molecular detection of toxin-producing C. difficile on a unformed stool specimen collected on or after the third calendar day of admission to a room.
“Directly following room cleaning, UV disinfection devices are placed in the room to deliver UV in 2 or 3 positions, with a 5-minute run time per position,” the study states. “A room with a bathroom has 3 UV device positions per room (on either side of the bed and in the bathroom). If the room does not have a bathroom, 2 positions are used (on either side of the bed).”
Attia says that “even if microbe burden is decreased on surfaces that can be treated with UV, this in itself may not be sufficient to cut down C. difficile infection rates. The control of HA-CDI likely requires a multifaceted approach which includes not only maximal decontamination of the environment, but optimization of diverse factors from disinfection of medical equipment to antimicrobial stewardship.”
The study also notes that it’s unclear how some of the mitigating circumstances for the pulsed-xenon UV disinfection in the final stage of terminal room cleaning may have affected HA-CDI rates. “The control of HA-CDI likely requires optimization of a multifaceted approach, including: excellent hand hygiene compliance, early identification of those with CDI and possibly also those with C. difficile colonization, optimal environmental cleaning, dedicated medical equipment, excellent antimicrobial stewardship, and other measures that may enhance maximal decontamination of the environment,” the study states. “It is possible that one or more of these factors, if suboptimal, negated any positive.”
Attia reiterates that “it is known that UV disinfection can destroy microbes, including C. difficile spores. However, we have alluded to the many other factors that increase risk of C. difficile. At this point it is difficult to ascertain how much each risk factor contributes to overall risk of C. difficile, including the benefit of UV disinfection after manual cleaning at the time patients are discharged.”
Attia F, Whitener C, Mincemoyer S, Houck J, Julian K. The effect of pulsed xenon ultraviolet light disinfection on healthcare-associated Clostridioides difficile rates in a tertiary care hospital. Am J Infect Control. 2020;Jan 22. pii: S0196-6553(19)31083-1. doi: 10.1016/j.ajic.2019.12.019.