Ultraviolet-C Reduces Bacterial Pathogens in Hospital Rooms

Daniel M. Keller, PhD

November 02, 2012

SAN DIEGO, California — Automated ultraviolet-C (UVC) light emitters placed in hospital rooms after patients were discharged substantially reduced the contamination from several important pathogens, including spores, in real-world settings. Deverick Anderson, MD, MPH, from the Duke Infection Control Outreach Network in Durham, North Carolina, reported here at IDWeek 2012 that in a multicenter, prospective study, UVC was effective in decreasing levels of vancomycin-resistant enterococci (VRE), Clostridium difficile, and Acinetobacter both by direct line-of-sight and indirect (reflected) illumination.

"The environment plays a role in the transmission of pathogens in hospitalized patients," Dr. Anderson said in a news conference. "Many of the hospital environment surfaces aren't cleaned appropriately even in the best of situations...[and bacteria] can actually live on the environment long enough to be present when the next patient comes in." He said that on average, 50% of hospital room surfaces get missed by the environmental services in a terminal cleaning of a room between patients. Especially objects such as light switches and remote controls can often be missed.

UVC Reduced Bacterial Counts Even With Deck Stacked Against It

For this interventional study, performed in collaboration with the University of North Carolina at Chapel Hill, the researchers identified patients under contact precautions with infections caused by any of these bacteria at 2 tertiary care centers involving 9 hospitals. After the patients were discharged but before terminal room cleaning, the researchers took 3 environmental cultures from each of 5 or more locations in each patient room. Twenty-seven rooms had housed patients with VRE, 10 with C difficile, and 2 with Acinetobacter species.

The investigators then placed a commercial UVC-emitting device into each room. The rooms were illuminated with UVC until a bactericidal dose of 12,000 μWs/cm2 or greater was achieved for vegetative bacteria or 22,000 μWs/cm2 was achieved for spores. While the device was in operation, barriers at the door kept anyone from entering the room. Sensors had also been put in place.

The team then resampled the rooms, taking environmental cultures from the same 5 locations to compare the number of colony forming units (CFUs) before and after UVC treatment.

Culture sites included the bedside rail, bedside table, chair arm, over-bed table, sink, supply cart, toilet, shower floor, and bathroom floor next to the toilet.

In the 39 rooms analyzed, a greater than 1 log10 reduction in CFUs occurred in cultures from sites in both direct and indirect line of sight for all 3 organisms after UCV treatment compared with pretreatment cultures (see Table, below). The reductions were statistically significant for VRE and C difficile cultures but not for Acinetobacter species. Because of the low frequency of Acinetobacter infections in the target hospitals, the study was underpowered to detect such changes.

The investigators concluded that the UVC emitter significantly decreased the burden of VRE and C difficile pathogens in patient rooms and that the treatments were effective through both direct and reflected (indirect) exposure.

Dr. Anderson emphasized that the UVC treatment was performed before the standard terminal cleaning of the rooms between patients. "Essentially what we were trying to do is stack the cards against the machine, and even in that situation, it worked quite well," he said.

It remains unclear whether this sort of procedure would reduce transmission of the target pathogens or particular drug-resistant organisms. "We actually have a study going on right now. What we really need to determine is what actually happens to the next patient in the room," Dr. Anderson said. He expects those results in a couple of years.

At least 3 companies make UVC-emitting devices. Some are single units, and others use multiple emitters placed around the room. The cost of a complete system is in the neighborhood of $100,000, based on information from exhibitors at IDWeek 2012. The units themselves generally stand about 5 to 6 feet in height and calculate the dose of UVC by measuring either reflected light delivered or the amount of light emitted.

To kill vegetative forms of bacteria requires about 20 minutes. Spores require up to 40 minutes. These times are in addition to the standard room cleaning by environmental services. Using UV-reflective paint in hospital rooms could potentially reduce those times. Given the additional time and the costs of the machines, Dr. Anderson said they would have to be targeted to specific rooms as needed and not used in every room after every patient.

The infectious diseases and public health fields have "really woken up to the idea that environment is a very strong player in driving infection," said news conference moderator Liise-Anne Pirofski, MD, chief of the Division of Infectious Diseases at Albert Einstein College of Medicine and Montefiore Medical Center in New York City and an IDWeek 2012 chair. "So I think that research that focuses on ways to be decontaminating rooms is going to be extremely important."

She added that the public is extremely concerned about infections, and many groups are focusing on hospital-acquired infections. "So I think that innovation that assures the public that their [hospital] rooms are protected would probably bring a lot of public confidence," she said.

Table: UVC Decontamination of Patient Rooms (Combined Direct and Indirect UVC Exposures)

Organism CFU Before UCV CFU After UCV CFU Reduction (%) CFU Reduction (log10) P-Value
VRE 712 15 98 1.68 < .001
C difficile 724 51 93 1.15 < .001
Acinetobacter 52 1 98 1.71 .25


Lumalier Inc, a manufacturer of one of the UVC-emitting devices, lent 8 machines but had no input into the study design, data review, or poster presentation. Dr. Anderson is a grant investigator and is on the Speaker's Bureau of Merck. He has a licensing and royalty agreement with UpToDate Online. Dr. Pirofski has disclosed no relevant financial relationships.

IDWeek 2012. Abstract 929. Presented October 19, 2012.