48 Methods
We performed a prospective cohort study at 2 hospitals: Duke University Hospital (a 921-bed tertiary-care academic medical center in Durham, North Carolina) and Duke Regional Hospital (a 250-bed community hospital in Durham, North Carolina). The study was designed to characterize the baseline and temporal profile of microorganisms on environmental surfaces of acute-care hospital rooms and on patients admitted to these newly disinfected rooms. We sought to characterize the nature of bacterial transfer events between patients and environmental surfaces using 4 ‘mar- ker’ MDROs: methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Clostridium difficile ,and multidrug-resistant (MDR) Acinetobacter baumannii. These organisms were chosen due to their importance as pathogens in HAIs and their propensity to contaminate and persist on hospital surfaces.2 The study was approved by the Duke University Health Sys-
tem Institutional Review Board and was registered on Clin-
icalTrials.gov (trial no. NCT01803100). Additionally, the current study was performed in the study hospitals contemporaneously with the BETR Disinfection study (trial no. NCT01579370),4 the first controlled, cluster-randomized multicenter study investigat- ing the efficacy of reducing incidence of HAIs with use of enhanced terminal cleaning strategies. In short, participating hospitals were randomized to terminally clean all patient rooms with (1) reference (quaternary ammonium disinfectant except for C. difficile, for which bleach was used); (2) UV (quaternary ammonium disinfectant and disinfecting ultraviolet [UV-C] light except for C. difficile, for which bleach and UV-C were used); (3) bleach only; or (4) bleach and UV-C. Every strategy was used at each hospital in 4 randomly assigned consecutive 7-month peri- ods. Thus, each participating hospital would implement all 4 cleaning strategies for 6 months with 1 month of washout between different cleaning methods. The routine daily cleaning of the patient rooms continued during the study with quaternary ammonium for all rooms or bleach for rooms that had housed patients with Clostridium difficile infection (CDI) according to standard practice at participating hospitals. We enrolled 20 sub- jects for each type of terminal disinfection strategy.
Subject enrollment
We prospectively identified subjects for enrollment using the admissions and transfer data from of the health system electronic medical record. All patients admitted to newly cleaned rooms at participating hospitals were eligible. To enhance the ability to detect and document bacterial transmission events between patients and hospital environments, study personnel specifically sought out (1) patients housed in rooms whose antecedent patient was placed on contact precautions for any reason and (2) patients with anticipated hospital stay of≥48 hours. Informed consent was obtained from all subjects enrolled in the study. Patients were excluded if they had already been placed in the newly cleaned room prior to screening procedures, baseline sampling, or informed consent.
Specimen collection
Study personnel made study visits to collect specimens from the patient and environmental room surfaces at the time of enroll- ment (day 0) and at defined intervals thereafter (ie, study days 3 and 7 and each week after study enrollment). Importantly, the
Luke F. Chen et al
environmental specimens were obtained on day 0 after terminal disinfection but prior to subject entry into the room. Where possible, a final set of specimens was collected from the patient and environmental room surfaces on the day of discharge from the room. Study personnel performed hand hygiene and donned contact isolation equipment prior to entering the room and taking microbiological specimens to reduce introduction of microorganisms. Study personnel obtained 2 microbiological swabs from 4 body
sites (nares, oropharynx, axilla, and perineum) at each study visit5,6 and a fecal specimen if available on the day of the visit.7,8 Microbiological samples were also collected from 7 high- frequency touch surfaces in the hospital room of the enrolled subject; these surfaces included the bed rail, overbed table, top of the nearest bedside table, arm rest of chair, sink, toilet seat, and the floor of the shower bloc.9 Each surface area was sampled repeatedly using 10 individual Rodac plates (5 for aerobic and 5 for anaerobic culture) to enhance microbiological yield and to reduce sampling error.10
Outcomes
We identified 2 primary outcomes of interest: (1) The baseline and subsequent patterns of patient colonization and hospital surface contamination, and (2) the number of microbiological and molecularly proven bacterial transfer events between hospital surfaces and patients. We also identified 2 secondary outcomes of interest: (1) the direction and timing of bacterial transfer events and (2) the clonal relatedness of bacterial isolates involved in transfer events. We defined microbiological bacterial transfer (MBT) events as the detection of microorganisms from patients and environmental surfaces of the same genus, species, and antibiotic susceptibility (for MRSA and VRE). The likely direction of bacterial transmission was surmised based on the sequence of detection. For example, if an organism was found on environ- mental surfaces prior to identification in patient specimens, we categorized the MBT event as an environment-to-patient trans- mission. If an organism was detected on patient and environ- mental specimens at the same study visit, the direction of the MBT was defined as indeterminate. Microbiological methods for patient-derived specimens, spe-
cimens from environmental sampling and the molecular analysis and relatedness testing are described in detail in the supplemental appendix.
Statistical analysis
We used standard descriptive statistics, including medians and interquartile ranges (IQRs) for nonnormally distributed con- tinuous variables. For quantitative analyses of data from Rodac plates, culture results were aggregated to obtain the number of colony-forming units (CFUs) per environmental site, not per plate.10
Results Demographics
We enrolled and collected data on 80 patient–room encounters that occurred in 68 general ward rooms; 67 of the patients (84%) were white, and 54 (68%) were female (Table 1). Collectively, 79% of the enrolled patients were admitted under 2 medical services:
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