Infection Control & Hospital Epidemiology
Table 1. Demographic and Admission Characteristics of Subjects Enrolled in the Current Study
Variable
Age, y, median (IQR) Female
Caucasian
General medicine service Oncology
Only 1 collection 2 collections ≥3 collections
Length of hospital stay, d median (IQR) Note. IQR, interquartile range.
Full Cohort (N=80), No. (%) 60 (55–69) 54 (68) 67 (84) 22 (28) 29 (36) 15 (19) 48 (60) 17 (21)
4.9 (3.1–12.0)
49
Table 2. Baseline Contamination of Hospital Surfaces at Enrollment by Pathogen
Variable
Rooms with contamination, no. (%)
MRSA VRE
Clostridium difficile Acinetobacter
15 (18.8) 18 (22.5) 21 (26.3) Median CFU/cm2 (IQR) 6 (3–13) 8 (5–38) 3 (1–11) 9 (11.3) 4 (1–9)
Note. MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant enter- ococci; CFU, colony-forming units; IQR, interquartile range.
encounters (2.5%). Notably, 1 of these patients (1.25%) was concurrently colonized with MRSA and C. difficile. Hospital room surfaces were contaminated with MDROs
despite terminal disinfection in 44 of 80 patient rooms (55%) at time of study enrollment. Clostridium difficile was detected in 21 rooms (26.3%); VRE was detected in 18 rooms (22.5%); MRSA was detected in 15 rooms (18.8%); and MDR Acinetobacter was detected in 9 rooms (11.3%). Contamination with multiple MDROs was observed in 19 (23.8%) rooms; 2 MDROs were identified in 17 rooms (21.3%), and 3 MDROs (2.5%) were identified in 2 rooms. The bioburden of MDROs on tested hospital surfaces was
generally low at enrollment (median, 6 CFU of MDROs/cm2; interquartile range [IQR], 2–16 CFU/cm2). Notably, the bio- burden was similarly low regardless of the organism detected (Table 2).
Bacterial transfer events
Fig. 1. Included and excluded study patients and results of bacterial transfer events. Percentages of the total population displayed. MTE, microbiological transfer event; ME, microbiologically evaluable.
general medicine and oncology/hematology. The median length of hospital stay for enrolled patients was 4.9 days. Of the 80 patients, 15 (18.8%) were discharged before the day 3 study visit and provided only baseline specimens (Fig. 1). The remaining 65 patient–room encounters (81.3%) provided the baseline and at least 1 other pair of patient–environmental specimens on sub- sequent study visits for comparison; this group of 65 patients were considered the microbiologically evaluable (ME) cohort.
Baseline and temporal pattern of patient colonization and surface contamination
In total, 9 patients (11.3%) were asymptomatically colonized with MDROs at study entry: MRSA colonization was observed in 6 encounters (7.5%), VRE colonization was observed in 2 encounters (2.5%), and C. difficile colonization was found in 2
We detected 12 microbiological bacterial transfer (MBT) events (18.5%) among the 65 patients of the ME cohort: 2 (16%) were associated with MRSA, 5 (42%) were associated with VRE, and 5 (42%) were related to C. difficile (Tables 3). We categorized these 12 MBT events into 3 categories based on likely direction of bacterial transfer (Table 3): 4 MBT events (33%) occurred from patient to environment; 4 events (33%) occurred from environ- ment to patient; and in 2 environment-to-patient transfer events (50%), a molecularly similar organism was detectable on hospital room surfaces at baseline. The other 2 apparent environment-to- patient MBT events involved molecularly dissimilar organisms of the same genus and species. Notably, 4 MBT events (33%) were of indeterminate direction because a marker organism was detect- able in both the patient and the environment at the same post- baseline visit. We attempted to perform molecular relatedness testing on
patient and environmental isolates obtained from these 12 MBT events; however, 3 patient-derived VRE isolates failed to amplify despite repeated attempts. Thus, complete clonal relatedness data were only available for 9 (75%) of 12 MBT events (Table 3). Molecular sequencing of isolates captured in MBT events showed that MDRO transmission frequently involved both molecularly related and molecularly dissimilar isolates of the same organism. For instance, 3 MBT events (33%) involved molecularly dissimilar isolates (ie, not true transmission events), and 4 other MBT events (44%) involved a combination of molecularly dissimilar and molecularly related isolates. Only 2 MBT events (22%) involved strictly molecularly related isolates. Moreover, 4 distinct MRSA pulsotypes were identified in the 2
MBT events (Supplemental Fig. 1). None of the pulsotypes mat- ched control MRSA types tested (ie, USA 100, 200, 300, 400, 500,
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