Carbapenem-resistant Enterobacteriaceae (CRE) are associated with mortality and morbidity.Reference Gupta, Limbago, Patel and Kallen ¹ Cleaning of high-touch surfaces (HTSs) in the near-patient environment is often suboptimal.Reference Boyce, Havill, Lipka, Havill and Rizvani ^{2 ,} Reference Rupp, Adler and Schellen ³ Significant interest has been directed toward novel “no touch” disinfection mechanisms such as ultraviolet (UV) light for removal of multidrug-resistant organisms from patient rooms.Reference Dancer ⁴ To our knowledge, UV light as a mechanism for removal of CRE from a patient room has not been investigated. In this study, we assessed the efficacy of UV light treatment at reducing CRE in a patient room, and we sought to ascertain whether there is a difference in CRE reduction based on organism (ie, K. pneumoniae vs E. coli vs E. cloacae).

This study was performed in an empty patient room of The Johns Hopkins Hospital in September 2015. Using methods similar to those previously described,Reference Rutala, Gergen and Weber ⁵ a template of a single contact plate (Becton Dickinson, San Jose, CA) was drawn on Formica swatches 12.7 cm×17.8 cm (5×7 inches). A 10 µL aliquot of a 0.5×10⁷ inoculum of a single CRE type was spread onto the contact plate template using a sterile, glass, hockey-stick–shaped spreader. The inoculated swatches were attached to a minimum of 17 high-touch surfaces (HTSs) in the patient room and bathroom. HTSs included those defined by the Centers for Disease Control and Prevention: bed rail, IV pump, vitals monitor, keyboard, over-bed tray table, call box, sink, shower curtain, and toilet seat. ⁶ Each HTS was within ~8 feet of the UV device during at least 1 cycle.

The UV-C Clorox Healthcare Optimum-UV device (Clorox, Oakland CA) emits UV-C light at a wavelength of 254 nm via 157.5-cm (62-inch) maximum-output mercury lamps. This equipment was activated for 5 minutes on each side of the patient bed and 5 minutes in the bathroom (ie, a total of 15 minutes). A contact plate was then pressed onto each swatch. Plates were incubated at 37°C for 48 hours. Total colony-forming units (CFUs) were counted, and CREs were identified. This cycle was repeated for each CRE organism. Color change from yellow to dark green on device dose indicators were used to verify that UV light adequate to kill Clostridium difficile and methicillin-resistant Staphylococcus aureus was emitted. Negative controls (ie, inoculated swatches placed in a box to prevent exposure to UV) were used for all cycles. Proportions of plates with no growth of CRE (or no growth of any organism) post exposure to UV were compared using Fisher’s exact test.

A total of 133 HTSs were sampled: 34 with E. coli, 47 with K. pneumoniae, and 52 with E. cloacae. All negative control swatches grew organisms too numerous to count (TNTC), indicating that any reduction on other swatches was due to UV-C exposure. Only 2 of the plates (1.5%) grew any CRE after exposure to UV light: both E. cloacae plates grew cultures; 3 plates grew CFUs from a bedrail; and a plate from a shower curtain grew CRE TNTC. The other 131 plates did not grow any CRE, demonstrating a 6 log reduction in CRE. Seven plates (5.3%) grew non-pathogenic organisms (eg, filamentous Bacillus organisms).

These results show that UV light treatment was highly effective at killing CRE (K. pneumoniae, E. coli, and E. cloacae) on HTSs in a patient room and bathroom with 15 minutes of exposure. We found complete reduction of CRE from 25 different HTSs in the patient room and bathroom, including the IV pump, vitals monitor, call bell, keyboard, and toilet seat. The only 2 sites where we found growth of CRE (E. cloacae) after UV treatment were a shower curtain and a bed rail. The shower curtain swatch, which grew CRE TNTC, was between 2 curtain folds, and we hypothesize that this area was not exposed to UV light. The privacy curtain in the patient room, which was not folded had complete reduction of CRE, highlights the importance of setting the HTSs to maximize surface exposure to UV, such as straightening the curtains. We found no difference in reduction based on organism. A recent study has suggested that K. pneumoniae may persist in the near-patient environment longer than E. coli or other Gram-negative organisms.Reference Guet-Revillet, Le Monnier and Breton ⁷ Our study shows that UV light treatment removes K. pneumoniae from HTSs as effectively as it removes other Gram-negative organisms.

The limitations of this study include that it was simulated, even though it was performed in an actual patient room. We inoculated HTSs with CRE concentrations that were likely higher than would be seen under patient-care conditions, and we achieved a nearly complete reduction. These results support the likelihood that the lower burden of contamination during actual patient care would also be adequately reduced by UV treatment.

UV technology is an effective method to disinfect CRE from high-touch surfaces in the patient-care environment. Methods such as this may become increasingly important as antimicrobial-resistant Gram-negative pathogens continue to emerge. The short cycle time makes UV disinfection a realistic option for daily disinfection of patient rooms. Studies are needed to evaluate the efficacy of this technology to decrease patient infections and transmission of pathogens in the healthcare setting.