Clostridium difficile infection is the most common cause of healthcare-associated diarrhea, which can potentially lead to costly and life-threatening complications.Reference Zhang, Palazuelos-Munoz, Balsells, Nair, Chit and Kyaw 1 Spores shed in high numbers by C. difficile–colonized or –infected patients are resistant to some disinfectants and can be difficult to eradicate from the hospital environment by manual cleaning.Reference Ali, Moore and Wilson 2 Spores remain viable for long periods on surfaces and may be a source of infection, so reducing environmental contamination by C. difficile may decrease the risk of transmission.
Although disinfectants with sporicidal activity may be used during manual cleaning, it can be difficult to ensure that staff members are consistent in applying the correct concentrations and to ensure full coverage of surfaces in a clinical setting. Sublethal concentrations of disinfectants allow bacteria to persist on surfaces, and continued exposure may promote the development of tolerance. If an insufficient volume of disinfectant is used on cloths or mops during cleaning, wet contact time is reduced and drying promotes transfer and spread of spores.
At a large teaching hospital, whole-room aerial decontamination with hydrogen peroxide vapor (HPV) after patient discharge has been introduced to supplement manual cleaning in an effort to eradicate environmental reservoirs of C. difficile spores.Reference Ali, Moore and Wilson 2 , Reference Ali, Muzslay, Bruce, Jeanes, Moore and Wilson 3 A sensitive method to detect C. difficile in the environment was developed in earlier work.Reference Ali, Moore and Wilson 2 Sampling of surfaces in the patient rooms after manual cleaning (routine/terminal cleaning) and after enhanced cleaning (hydrogen peroxide decontamination) was implemented to identify reservoirs of C. difficile contamination and to direct cleaning toward areas most frequently demonstrating residual spores. Using sponge swabs, it was possible to isolate and quantify the amount of C. difficile bioburden on each surface. Where contact plates are limited to 25-cm2 sample areas, sponge swabs allow quantitative sampling of larger areas with greater sensitivity.Reference Ali, Muzslay and Wilson 4 The purpose of this study was to determine the surfaces in the ward environment where C. difficile most commonly persist after routine cleaning or terminal disinfection with and without hydrogen peroxide decontamination in order to refine cleaning protocols.
METHODS
Clinical Setting and Selection Criteria
At a London teaching hospital, single-isolation patient rooms and patient bed bays were selected randomly when terminal cleaning was requested regardless of the C. difficile infection status of the patient just discharged. All rooms and bed bays were selected between 9:00 and 17:00 on week days. No other selection criteria were applied. No room or bed bay was sampled more than once after it had been disinfected with aerial hydrogen peroxide. Rooms were cleaned daily at variable times. Sampling was conducted immediately before and after terminal cleaning and hydrogen peroxide decontamination. Patients that recovered from diarrhea but still carried C. difficile were defined as colonized.
Decontamination and Cleaning Policy
All routine cleaning and terminal cleaning was performed manually using microfiber cloths (for surfaces) and microfiber mops (for floor areas) pretreated with a peracetic acid-based disinfectant (DiffX, MTP Innovations, UK)Reference Humphreys, Finan and Rout 5 and prepared in house by domestic cleaning staff. Both routine and terminal cleaning applied to all reusable equipment, furniture, nonporous surfaces, and floors.
Routine cleaning was performed while a patient was present in the room using microfiber and disinfectant at a concentration of 1,000 ppm for all surfaces. A higher concentration (3,000 ppm) was only used when sporicidal activity was needed (eg, patient had diarrhea) to limit cost. Floors were mopped with solution at 750 ppm. A sachet of peracetic acid–generating powder (20 g) was dissolved in 1–4 L of warm water (as required) with a 20-minute dwell time.Reference Humphreys, Finan and Rout 5 Equipment, curtains, bed handrails and frames, furniture, doors, window sills, and call bells were cleaned with cloths soaked in the solution. Surfaces were dusted and floors were mopped both dry and wet. Spot cleaning was done by nurses with detergent or sporicidal wipes (Clinell, Gama Healthcare, UK). When the patient was discharged or moved to another room, terminal cleaning was performed. Peracetic acid cloths were used to clean mattresses, bed frames, clean equipment, surfaces, call bells, entertainment systems, lockers, bed tables, furniture, switches, and ceiling vents. Bedding and crockery were removed. The walls were washed and curtains were removed (if an infected patient had been present) and the floor was mopped both dry and wet. If the patient had a known infection due to C. difficile, norovirus, vancomycin-resistant enterococci or multidrug-resistant organisms, terminal cleaning was followed by decontamination using the Deprox system (Hygiene Solutions, UK), operated by dedicated personnel provided by the manufacturer. Aerial concentrations of hydrogen peroxide were 29–46 ppm at peak and at a mean of 3.3 ppm at end of cycle, with mean peak delta relative humidity of 15.4% and a cartridge concentration of 4.9%.Reference Ali, Yui, Muzslay and Wilson 6
Sampling Sites and Processing of Swabs
Up to 16 sites in patient single-isolation rooms and up to 10 sites in the bed-bay areas were selected to represent high-frequency touch sites within and beyond the near-patient vicinity and difficult-to-clean surfaces.
As previously described, surfaces were sampled with sponge swabs (Technical Service Consultants, UK) premoistened with 10 mL neutralizer solution (0.1% sodium thiosulphate, 3.0% Tween 80, 0.3% lecithin prepared in phosphate-buffered saline [PBS]).Reference Ali, Muzslay, Bruce, Jeanes, Moore and Wilson 3 Sponge swabs were transferred into sterile blender bags (VWR, UK) containing 30 mL neutralizer solution and were manually homogenized (massaged between the fingertips) for 30 seconds. The solution was passed through a 0.45-µm nitrocellulose filter membrane (Advantec, Ehime, Japan) by syringe filtration. Filter membranes were plated onto Braziers selective agar plates (90 mm diameter; Oxoid, UK) and incubated anaerobically at 37°C for 48 hours. Presumptive C. difficile colonies were isolated using standard microbiology techniques (ie, colony morphology, odor, Gram staining) and were confirmed using a latex agglutination test (Oxoid, UK). Results of sampling were reported back to facilities staff on a fortnightly basis to highlight the surfaces most likely to harbor residual contamination.
Statistical Analysis
Means (±standard deviation) were compared using a χ2 test. One-tailed tests were used for all analyses, and differences were considered statistically significant when P<.05.
RESULTS
Over a period of 1 year, 2,529 clinical sites in 146 single-isolation rooms and 44 bed bays were sampled for vegetative and spore C. difficile contamination. In bed areas occupied by known C. difficile–infected or –colonized patients, C. difficile was recovered from 83 of 213 sites (38.9%) of samples after routine cleaning, from 56 of 272 sites (20.6%) after terminal cleaning, and from 23 of 276 sites (8.3%) after hydrogen peroxide decontamination. In bed areas where the C. difficile status of the occupying patient was unknown, C. difficile was recovered from 48 of 359 sites (13.4%) after routine cleaning, from 49 of 687 sites (7.1%) after terminal cleaning, and from 20 of 691 sites (2.9%) after hydrogen peroxide decontamination (Table 1).
Percentage of Sites Positive for C. difficile Contamination After Cleaning
NOTE. HPV, hydrogen peroxide vapor system.
The floor corner and bathroom floor were the sites most frequently positive for C. difficile contamination after routine cleaning and terminal cleaning. Hydrogen peroxide decontamination reduced the numbers of spores and frequency of C. difficile isolation but was less effective on the bathroom floor, where 9 of 57 surfaces (15.8%) remained contaminated.
Ceiling vents were identified as reservoirs of C. difficile, with 6 of 19 sites (31.6%) positive after terminal cleaning. Decontamination of these surfaces was not stipulated within the criteria for routine cleaning; only the exposed surfaces of the vent were cleaned as part of the terminal cleaning protocols. All vents were covered and sealed during hydrogen peroxide decontamination to avoid circulation and spread to adjacent areas via the duct work. Despite enhanced cleaning, C. difficile persisted on 6 of 18 vents (33.3%). Notably, where single isolation rooms were decontaminated, C. difficile was isolated on the outer door handles after both terminal cleaning (2 of 61; 3.3%) and hydrogen peroxide decontamination (4 of 61; 4.9%).
The efficacy of removal of C. difficile was assessed over 4 periods of 3 months in 2013–2014 (Table 2). During the first quarter (January –March), C. difficile was recovered from 31 of 101 sites (30.7%), from 43 of 347 sites (12.4%), and from 25 of 390 sites (6.4%) of after routine cleaning, terminal cleaning, and terminal cleaning with hydrogen peroxide decontamination, respectively. Following feedback of the commonly contaminated sites to the cleaners, these numbers decreased to 28 of 134 sites (20.9%), 25 of 304 sites (8.2%), and 6 of 256 sites (2.3%), respectively, by the third quarter of the year (July–September). The reduction in recovery after hydrogen peroxide was significant between the first and third quarters (P<.05). Clostridium difficile isolated after terminal cleaning decreased from 12.8% to 8.2% between the second quarter (April–June) and the third quarter, suggesting an improvement in cleaning technique because there was no change in C. difficile after routine cleaning for the same period (Table 2). This improvement coincided with increased training of the cleaning staff on the use of warm water to activate the disinfectant, coverage and the surface area to be cleaned by each mop or cloth, and the quality of the microfibers, as observation by supervisors showed some deficiencies. The concentration of the solution could not be checked at the time.
C. difficile Positive Sites Over Assessment Periods After Routine Cleaning, Terminal Cleaning, and Terminal Cleaning With Hydrogen Peroxide Decontamination in 2013–2014
NOTE. HPV, hydrogen peroxide vapor system.
a P=.03; χ2 test.
The method used for sampling allowed quantitative measurement of the amount of C. difficile on each surface (Table 3). The most contaminated surfaces by number of colonies were the nurse call buttons, bathroom floors, and floor corners. Terminal cleaning reduced the amount of C. difficile on all surfaces with the exception of the ceiling vent. Hydrogen peroxide decontamination further reduced contamination in rooms that had recently housed colonized patients (Table 4).
Clostridium difficile Contamination on Surfaces After Cleaning
NOTE. CFU, mean colony-forming units; SD, standard deviation; HPV, hydrogen peroxide vapor system.
Clostridium difficile Contamination in Bed Areas After Cleaning
NOTE. HPV, hydrogen peroxide vapor system; SIR, single isolation room; SD, standard deviation.
aCounts expressed as mean colony forming units (CFU) per single isolation room (SIR) or bed bay (± standard deviation).
During the study, rates of C. difficile infections were reported to Public Health England. Stool samples were tested without selection, both formed and unformed. The hospital-apportioned C. difficile rate per 100,000 patient bed days was 37.1 in 2013–2014, 40.2 in 2014–2015 and 36.2 in 2015–2016. Cancer and medical specialties accounted for 60% of the patients with C. difficile in the hospital, and this proportion increased over the study period.
DISCUSSION
In the healthcare setting, acquisition of C. difficile infection is associated with environmental contamination as much as it is associated with person to person spread.Reference Otter, Yezli, Salkeld and French 7 Previous occupants of the same bed area who were infected with pathogens that survive well in the environment are a risk factor for acquisition of the pathogen.Reference Mitchell, Dancer, Anderson and Dehn 8 Clostridium difficile spores persist in the environment up to 5 months. Reference Mitchell, Dancer, Anderson and Dehn 8 A retrospective cohort study demonstrated that even the administration of antibiotics to patients previously occupying a bed increased the risk of the next patient in that bed acquiring C. difficile. Reference Freedberg, Salmasian and Cohen 9 Improved hand hygiene and source isolation can reduce transmission between patients, but C. difficile persists in the environment with a wide range of ribotypes present, most likely disseminated by asymptomatic patients.Reference Eyre, Cule and Wilson 10 Previous studies in this hospital have shown that hydrogen peroxide systems are effective in reducing C. difficile in the environment.Reference Ali, Muzslay, Bruce, Jeanes, Moore and Wilson 3 Furthermore, the use of hydrogen peroxide or ultraviolet irradiation to decontaminate single-isolation rooms after discharge of the patient is associated with a gradual reduction in the incidence of C. difficile infections in patients.Reference Pegues, Han, Gilmar, McDonnell and Gaynes 11 , Reference McCord, Prewitt, Dyakova, Mookerjee and Otter 12 A large-cluster, randomized study of various types of terminal disinfection across 9 hospitals showed addition of UV-C to standard cleaning reduced the overall chance of a patient acquiring 1 of the 4 target organisms from a previous occupant.Reference Anderson, Chen and Weber 13 However, the incidence of C. difficile infection was not significantly different with or without UV-C devices, nor were spore counts affected significantly in 92 rooms that were sampled. The tests were made at 10 sites using 10 Rodac plates each (5 with aerobic media and 5 with anaerobic media, 125 cm2). For C. difficile using general anaerobic media, only 2.9 to 4.5 mean colony-forming units (CFU) per room were detected. In contrast, the current study used hydrogen peroxide and a more sensitive environmental detection method.
The rate of isolation of C. difficile from the environment following routine daily cleaning or terminal disinfection did not change significantly between the start and finish of the intervention period, suggesting that feedback of sites requiring additional cleaning to the cleaners had limited effect. However, there was a significant reduction over time in residual C. difficile numbers following hydrogen peroxide decontamination. The number of patients entering the hospital with C. difficile was not known because there was no universal screening. Any effect on the incidence of C. difficile infections was confounded by a rising number of cancer patients admitted.
Many more bed areas contained sites where C. difficile was detected than had housed patients known to be carrying the organism. Contamination was found in 38.9% of sites after routine cleaning in patient bed areas occupied by patients known to be colonized with C. difficile. In bed areas with no known C. difficile patients, contamination was found in 13.4% of sites. After discharge of the patient, rooms were terminally cleaned in preparation for subsequent patients, but 10.6% of sites sampled remained positive. Manual cleaning alone, even to the terminal disinfection standard, was inadequate to eradicate environmental contamination by C. difficile. The need for monitoring the environment and the methods used have been extensively reviewed. 14 The main weakness of monitoring methods lies in not knowing the safe level of contamination with respect to preventing transmission.
A weak association has been reported previously between audit and feedback of cleaning performance using fluorescent markers and reduced rates of C. difficile infection.Reference Smith, Taggart, Lebovic, Zeynalova, Khan and Muller 15 Such markers were not used during this study, but audit and immediate feedback of cleaning standards by domestic supervisors by direct observation and using ATP (AdenosineTri-Phosphate) bioluminesence (Clean-Trace Clinical Hygiene Monitoring System, 3M Health Care Ltd. Loughborough, UK) had been in use at this hospital for several years.Reference Moore, Smyth, Singleton and Wilson 16 Although not specific to bacteria, this method provides real-time results and indicates the adequacy of removal of organic debris from a surface to a level below a predetermined threshold that may be immediately relayed to the cleaner.
Aerial hydrogen peroxide was effective in reducing the level of contamination after terminal cleaning but had limited effect in areas where shielding occurred or when debris remained. In some areas, such as the bathroom floor, C. difficile persisted despite terminal disinfection and use of hydrogen peroxide. Previous studies here have shown uneven distribution of hydrogen peroxide, which may result in lower efficacy in en-suite bathrooms.Reference Ali, Moore and Wilson 2 The hydrogen peroxide decontamination system used in this study consisted of a single unit. Systems are available that combine an HPV generation unit with 1 or more aeration units to aid distribution. In some cases, failures of eradication of pathogens have been reported, but direct comparative trials between systems are needed.Reference Gray 17
Hydrogen peroxide vapor systems, as used in this study, deliver 3%–7% hydrogen peroxide with or without silver ions, and they reduce spores by at least 4 log10 CFU.Reference Boyce 18 A microcondensation HPV system that uses 35% hydrogen peroxide has been reported to reduce counts by 6 log10 CFU.Reference Otter and French 19 A trial at this hospital suggested similar efficacy against various pathogens, including C. difficile spores, between the 2 HPV types.Reference Ali, Muzslay, Bruce, Jeanes, Moore and Wilson 3 Another study compared the same vaporizor system and an aerosolizer using hydrogen peroxide and peracetic acid and found similar reductions in environmental load, but C. difficile spores were not tested in this study.Reference Blazejewski, Wallet and Rouzé 20
Decontamination failures are often associated with physical obstruction. In this study, the bed control and nurse call button were initially left in holders during aerial decontamination. However, this may have shielded the posterior surface of the device from hydrogen peroxide. A change in protocol to suspend these items prior to the decontamination process was implemented to improve exposure. Ceiling vents must be sealed during decontamination to prevent leakage of hydrogen peroxide to other areas. Consequently, C. difficile spores remained in the vents. Ceiling vents and vent covers must therefore be included in all manual cleaning protocols. If local infrastructure allows, isolating air flow instead of using covers may be beneficial to allow hydrogen peroxide decontamination of vents.
Nurse call buttons were the most highly contaminated surfaces after both routine and terminal cleaning. This high-frequency touch surface, regularly used by patients, may be an important reservoir of C. difficile. This finding highlights the importance of hand hygiene policies for staff, patients, and visitors. Whole-room aerial decontamination was effective at reducing C. difficile on surfaces inaccessible or hard to reach by manual cleaning. However, effective removal of dirt and organic debris by manual cleaning was essential for highest efficacy and may have improved as a result of feedback.
Manual cleaning was often insufficient to remove all C. difficile from the environment. Identification of highly contaminated sites led to a temporary improvement in terminal cleaning of affected areas and reduction in C. difficile isolated. Removal of soil was important in improving the long-term efficacy of hydrogen peroxide decontamination with the aim of reducing the risk of transmission.
ACKNOWLEDGMENTS
The authors acknowledge and thank Nives Pupovac for assistance in facilitating the work and for advice. This project was supported by researchers at the National Institute for Health Research University College London Hospitals Biomedical Research Center. Ethics approval was not required because no patients were involved.
Financial support: This work was funded by University College London Hospitals NHS Trust. The work was performed as a service evaluation of hydrogen peroxide used to decrease the risk of C. difficile infection. The funder did not influence the design of the study but a monthly review of the results was carried out as part of feedback. The manufacturer of the hydrogen peroxide system did not have any role in gathering or analysis of data or preparation of the manuscript.
Potential conflicts of interest: A.P.R.W. serves on advisory panels for 3M and Merck. All other authors report no conflicts of interest relevant to this article.
