Prior Room Occupant Research Articles

Editorial Commentary: Climbing the Evidentiary Hierarchy for Environmental Infection Control

Increasing concern over multidrug-resistant organisms (MDROs), especially vancomycin-resistant enterococci (VRE), Clostridium difficile, and multidrugresistant gram-negative bacteria (MDRGNB), has led to increasing attention being paid to the role of high-touch environmental surfaces in transmission. Our current understanding of the roles of environmental surfaces in MDRO transmission include the following: (1) a primary role with transmission from source patient to environmental surface to subsequent patient, and (2) a secondary role from source patient to environmental surface to hands of healthcare personnel to subsequent patient. Either a prior room occupant or a contemporaneous patient sharing reusable medical equipment is the source patient in most primary transmission events. Standard environmental cleaning and disinfection entails manual cleaning and application of a disinfectant, often utilizing a detergent disinfectant. In addition to new disinfectants with greater potency and shorter contact times, new technological advances include “nontouch disinfection” (NTD) methods, the most developed of which are hydrogen peroxide vapor (HPV), and automated germicidal ultraviolet irradiation. Both methods appear highly efficacious in inactivating the microbial bioburden present on surfaces, and both remove much of the variance inherent in human cleaning activity via a high degree of automation and feedback loops for verification that contact or irradiation times are adequate [1–3]. Despite these advances, demonstrating the clinical impact of both old and new environmental cleaning and disinfection technologies remains challenging. We propose an evidentiary hierarchy for assessing any environmental disinfection strategy (Figure 1), beginning with a foundation (ie, level I) of laboratory efficacy studies similar to those required for registration by the Environmental Protection Agency [4]. Numerous patient and practice factors confound the relationship between environmental bioburden reductions and MDRO transmission interruption, from the number of patients on antibiotics with wounds, devices, and diarrhea (rendering them either more contagious or susceptible to colonization), to rates of compliance with hand hygiene and isolation, to interventions aimed at source control such as chlorhexidine bathing. Because only a small proportion of all MDRO acquisitions lead to eventual infection, linking infection reductions to environmental bioburden reductions (ie, level V of Figure 1) is even more challenging. However, because infections correlate more closely than colonization with mortality, excess length of stay, and cost, such linkage will eventually become necessary to calculate the cost-effectiveness of new technologies. Such a hierarchy can assist the development of a new disinfection technology, guiding industry in demonstrating achievement at a lower level in the hierarchy before investment is made at a higher level. It also highlights the need for tools to link achievements at lower levels (eg, achievable log10 reductions in the laboratory or as part of an in-use study) to the likelihood of success at a higher level. Standardized methods for environmental and hand sampling, microbiologic cultures, and assessment of adherence to standard environmental cleaning, hand hygiene, and isolation precautions will all be important to make the climbing of this hierarchy more efficient. The report by Passaretti et al in this issue of Clinical Infectious Diseases, in which investigators found that HPV decontamination of MDRO patient rooms was associated with a 45% reduction in environmental contamination and 80% reduction in acquisition of VRE among patients with a prior MDRO-colonized Received 11 September 2012; accepted 18 September 2012; electronically published 5 October 2012. Correspondence: L. Clifford McDonald, MD, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Rd, MS07, Atlanta, GA 30333 (cmcdonald1@cdc.gov). Clinical Infectious Diseases 2013;56(1):36–9 Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved 2012. DOI: 10.1093/cid/cis845

Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit

The objective of this prospective cohort study was to determine whether admission to an intensive care unit (ICU) room previously occupied by a patient with multidrug-resistant (MDR) Gram-negative bacilli (GNB) increases the risk of acquiring these bacteria by subsequent patients. All patients hospitalized for >48 h were eligible. Patients with MDR GNB at ICU admission were excluded. The MDR GNB were defined as MDR Pseudomonas aeruginosa, Acinetobacter baumannii and extended spectrum β-lactamase (ESBL) -producing GNB. All patients were hospitalized in single rooms. Cleaning of ICU rooms between two patients was performed using quaternary ammonium disinfectant. Risk factors for MDR P. aeruginosa, A. baumannii and ESBL-producing GNB were determined using univariate and multivariate analysis. Five hundred and eleven consecutive patients were included; ICU-acquired MDR P. aeruginosa was diagnosed in 82 (16%) patients, A. baumannii in 57 (11%) patients, and ESBL-producing GNB in 50 (9%) patients. Independent risk factors for ICU-acquired MDR P. aeruginosa were prior occupant with MDR P. aeruginosa (OR 2.3, 95% CI 1.2–4.3, p 0.012), surgery (OR 1.9, 95% CI 1.1–3.6, p 0.024), and prior piperacillin/tazobactam use (OR 1.2, 95% CI 1.1–1.3, p 0.040). Independent risk factors for ICU-acquired A. baumannii were prior occupant with A. baumannii (OR 4.2, 95% CI 2–8.8, p <0.001), and mechanical ventilation (OR 9.3, 95% CI 1.1– 83, p 0.045). Independent risk factors for ICU-acquired ESBL-producing GNB were tracheostomy (OR 2.6, 95% CI 1.1–6.5, p 0.049), and sedation (OR 6.6, 95% CI 1.1–40, p 0.041). We conclude that admission to an ICU room previously occupied by a patient with MDR P. aeruginosa or A. baumannii is an independent risk factor for acquisition of these bacteria by subsequent room occupants. This relationship was not identified for ESBL-producing GNB.

Environmental Cleaning Intervention and Risk of Acquiring Multidrug-Resistant Organisms From Prior Room Occupants

Admission to intensive care unit rooms previously occupied by carriers of methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enteroccoci (VRE) had been found to confer a 40% increased risk of acquisition, presumably through environmental contamination. Subsequently, a cleaning intervention was shown to reduce MRSA and VRE room contamination. We now evaluate the effect of this intervention on the risk of acquiring MRSA and VRE from prior room occupants. We conducted a retrospective cohort study of patients admitted to 10 intensive care units at a 750-bed academic medical center during the enhanced cleaning intervention (from September 1, 2006, through April 30, 2008; n = 9449) vs baseline (from September 1, 2003, through April 30, 2005; n = 8203) periods. The intervention consisted of targeted feedback using a black-light marker, cleaning cloths saturated with disinfectant via bucket immersion, and increased education regarding the importance of repeated bucket immersion during cleaning. Intensive care units included medical, cardiac, burn/trauma, general surgery, cardiac surgery, thoracic surgery, and neurosurgery units. We calculated the number of room stays involving the potential for MRSA and VRE acquisition and then assessed the frequency at which eligible patients were exposed to rooms in which the prior occupants had MRSA-positive or VRE-positive status. Acquisition of MRSA and VRE was lowered from 3.0% to 1.5% for MRSA and from 3.0% to 2.2% for VRE (P < .001 for both). Patients in rooms previously occupied by MRSA carriers had an increased risk of acquisition during the baseline (3.9% vs 2.9%, P = .03) but not the intervention (1.5% vs 1.5%, P = .79) period. In contrast, patients in rooms previously occupied by VRE carriers had an increased risk of acquisition during the baseline (4.5% vs 2.8%, P = .001) and intervention (3.5% vs 2.0%, P < .001) periods. Enhanced intensive care unit cleaning using the intervention methods may reduce MRSA and VRE transmission. It may also eliminate the risk of MRSA acquisition due to an MRSA-positive prior room occupant.

Evaluation of Hospital Room Assignment and Acquisition of Clostridium difficile Infection

Clostridium difficile spores persist in hospital environments for an extended period. We evaluated whether admission to a room previously occupied by a patient with C. difficile infection (CDI) increased the risk of acquiring CDI. Retrospective cohort study. Medical intensive care unit (ICU) at a tertiary care hospital. Patients admitted from January 1, 2005, through June 30, 2006, were evaluated for a diagnosis of CDI 48 hours after ICU admission and within 30 days after ICU discharge. Medical, ICU, and pharmacy records were reviewed for other CDI risk factors. Admitted patients who did develop CDI were compared with admitted patients who did not. Among 1,844 patients admitted to the ICU, 134 CDI cases were identified. After exclusions, 1,770 admitted patients remained for analysis. Of the patients who acquired CDI after admission to the ICU, 4.6% had a prior occupant without CDI, whereas 11.0% had a prior occupant with CDI (P = .002). The effect of room on CDI acquisition remained a significant risk factor (P = .008) when Kaplan-Meier curves were used. The prior occupant's CDI status remained significant (p = .01; hazard ratio, 2.35) when controlling for the current patient's age, Acute Physiology and Chronic Health Evaluation III score, exposure to proton pump inhibitors, and antibiotic use. A prior room occupant with CDI is a significant risk factor for CDI acquisition, independent of established CDI risk factors. These findings have implications for room placement and hospital design.

P11.01 Resistance of Acanthamoeba spp. cysts to disinfection treatments

P11.01 Resistance of Acanthamoeba spp. cysts to disinfection treatments

Prior Environmental Contamination Increases the Risk of Acquisition of Vancomycin-Resistant Enterococci

Patients colonized with vancomycin-resistant enterococci (VRE) frequently contaminate their environment, but the environmental role of VRE transmission remains controversial. During a 14-month study in 2 intensive care units, weekly environmental and twice-weekly patient surveillance cultures were obtained. VRE acquisition was defined as a positive culture result >48 h after admission. To determine risk factors for VRE acquisition, Cox proportional hazards models using time-dependent covariates for colonization pressure and antibiotic exposure were examined. Of 1330 intensive care unit admissions, 638 patients were at risk for acquisition, and 50 patients (8%) acquired VRE. Factors associated with VRE acquisition included average colonization pressure (hazard ratio [HR], 1.4 per 10% increase; 95% confidence interval [CI], 1.2-1.8), mean number of antibiotics (HR, 1.7 per additional antibiotic; 95% CI, 1.2-2.5), leukemia (HR, 3.1; 95% CI, 1.2-7.8), a VRE-colonized prior room occupant (HR, 3.1; 95% CI, 1.6-5.8), any VRE-colonized room occupants within the previous 2 weeks (HR, 2.5; 95% CI, 1.3-4.8), and previous positive room culture results (HR, 3.4; 95% CI, 1.2-9.6). In separate multivariable analyses, a VRE-colonized prior room occupant (HR, 3.8; 95% CI, 2.0-7.4), any VRE-colonized room occupants within the previous 2 weeks (HR, 2.7; 95% CI, 1.4-5.3), and previous positive room culture results (HR, 4.4; 95% CI, 1.5-12.8) remained independent predictors of VRE acquisition, adjusted for colonization pressure and antibiotic exposure. We found that prior room contamination, whether measured via environmental cultures or prior room occupancy by VRE-colonized patients, was highly predictive of VRE acquisition. Increased attention to environmental disinfection is warranted.

Risk of Acquiring Antibiotic-Resistant Bacteria From Prior Room Occupants

Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) occurs during the care of patients harboring these organisms and may increase the risk of transmission to subsequent room occupants. Twenty-month retrospective cohort study of patients admitted to 8 intensive care units performing routine admission and weekly screening for MRSA and VRE. We assessed the relative odds of acquisition among patients admitted to rooms in which the most recent occupants were MRSA positive or VRE positive, compared with patients admitted to other rooms. Of 11 528 intensive care unit room stays, 10 151 occupants were eligible to acquire MRSA, and 10 349 were eligible to acquire VRE. Among patients whose prior room occupant was MRSA positive, 3.9% acquired MRSA, compared with 2.9% of patients whose prior room occupant was MRSA negative (adjusted odds ratio, 1.4; P = .04). VRE, Among patients whose prior room occupant was VRE positive, these values were 4.5% and 2.8% respectively (adjusted odds ratio, 1.4; P = .02). These excess risks accounted for 5.1% of all incident MRSA cases and 6.8% of all incident VRE cases, with a population attributable risk among exposed patients of less than 2% for either organism. Acquisition was significantly associated with longer post-intensive care unit length of stay. Admission to a room previously occupied by an MRSA-positive patient or a VRE-positive patient significantly increased the odds of acquisition for MRSA and VRE. However, this route of transmission was a minor contributor to overall transmission. The effect of current cleaning practices in reducing the risk to the observed levels and the potential for further reduction are unknown.