Nonimpact of Decolonization as an Adjunctive Measure to Contact Precautions for the Control of Methicillin-Resistant Staphylococcus aureus Transmission in Acute Care.

This was an observational study comparing methicillin-resistant Staphylococcus aureus (MRSA) transmission with no decolonization of medical patients to required decolonization of all MRSA carriers during two consecutive periods: baseline with no decolonization of medical patients (16 months) and universal MRSA carrier decolonization (13 months). The setting was a one-hospital, 156-bed facility with 9,200 annual admissions. Regression models were used to compare rates of MRSA acquisition. The chi-square test was used to compare event frequencies. We used rates of MRSA clinical disease as an outcome monitor of the program. Analysis was done on 15,666 patients who had admission and discharge tests; 27.9% of inpatient days were occupied by a MRSA-positive patient (colonized patient-days) who received decolonization while hospitalized during the baseline period (this 27.9% represented those who had planned surgery) compared to 76.0% during the intervention period (P < 0.0001). The rate of MRSA transmission was 97 events (1.0%) for 9,415 admissions (2.0 transmission events/1,000 patient-days) during baseline and was 87 (1.4%) for 6,251 admissions (2.7 transmission events/1,000 patient-days) during intervention (P = 0.06; rate ratio, 0.74; 95% confidence interval [CI], 0.55 to 1.00). The MRSA nosocomial clinical disease rate was 5.9 infections/10,000 patient-days in the baseline period and was 7.2 infections/10,000 patient-days for the intervention period (rate ratio, 0.82; 95% CI, 0.46 to 1.45; P = 0.49). Decolonization of MRSA patients does not add benefit when contact precautions are used for patients colonized with MRSA in acute (hospital) care.

The role of institutional epidemiologic weight in guiding infection surveillance and control in community and hospital populations.

BACKGROUND: Institutions such as hospitals, prisons, and long-term care facilities have been identified as focal points for the transmission of emerging infections. Cost-effective control of these infections in large populations requires the identification of optimal subpopulations for targeted infection control interventions. Our objective was to quantify and compare the relative impact that individual institutions or subpopulations have on wider population-level outbreaks of emerging pathogens. DESIGN: We describe a simple mathematical model to compute the epidemiologic weight (EW) of an institution or subpopulation. The EW represents the rate at which newly infectious individuals exit the institution under consideration. SETTING: A hypothetical academic tertiary-care hospital (700 beds, 5-day length of stay [LOS]) and prison (3098 inmates, 27-day LOS). PATIENTS: Individuals entering a hospital in-patient prison ward and nonprisoners entering both medical and surgical intensive-care units and those admitted to the general medical and surgical wards. RESULTS: The recent example of the community-acquired methicillin-resistant Staphylococcus aureus epidemic is used to illustrate the EW calculation. Hospitals and prisons, which often have vastly dissimilar populations sizes and LOSs and might have differing transmission rates, can have comparable EWs and thus contribute equally to an epidemic in the community. CONCLUSIONS: This method highlights the importance of measuring entrance and exit colonization prevalences for the optimal targeting of prevention measures. The EW not only identified superspreader institutions but also ranks them, enabling public health workers to optimize the allocation of resources to places where they are likely to be of most benefit.

Evaluation of multiple real-time PCR tests on nasal samples in a large MRSA surveillance program.

OBJECTIVES: We evaluated the LightCycler MRSA Advanced Test (Roche Molecular Diagnostics, Pleasanton, CA), the BD MAX MRSA assay (Becton Dickinson, Franklin Lakes, NJ), and the Xpert MRSA assay (Cepheid, Sunnyvale, CA) on nasal samples using the same population. METHODS: Admission and discharge nasal swabs were collected from inpatients using a double-headed swab. One swab was plated onto CHROMagar MRSA (CMA; Becton Dickinson, Sparks, MD) and then broken off into tryptic soy broth (TSB) for enrichment. TSB was incubated for 24 hours and then plated to CMA. The molecular tests were performed on the second swab. We analyzed the cost benefit of testing to evaluate what parameters affect hospital resources. RESULTS: A total of 27,647 specimens were enrolled. The sensitivity/specificity was 98.3%/98.9% for the LightCycler MRSA Advanced Test and 95.7%/98.8% for the Xpert MRSA assay, but the difference was not significant. The positive predictive value was 86.7% for the LightCycler MRSA Advanced Test, 82.7% for the Xpert MRSA assay (P > .1), and 72.2% and for the BD MAX MRSA test (P < .001 compared with the LightCycler MRSA Advanced Test). All three assays were cost-effective, with the LightCycler MRSA Advanced Test having the highest economic return. CONCLUSIONS: Our results suggest that the performance of the three commercial assays is similar. When assessing economic cost benefit of methicillin-resistant Staphylococcus aureus screening, the two measures with the most impact are the cost of the test and the specificity of the assay results.

Patient colonization and environmental contamination by vancomycin-resistant enterococci in a rehabilitation facility.

OBJECTIVES: To determine the frequency of environmental contamination in patient and common-use rooms and patient colonization by vancomycin-resistant enterococci (VRE). DESIGN: Cross-sectional study. SETTING: A 146-bed rehabilitation facility. PARTICIPANTS: Rectal cultures were collected from 74 (80%) of 93 patients. Environmental cultures were obtained from surfaces in 15 patient rooms (5 floors) and common-use areas on 8 floors. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gastrointestinal colonization of patients and environmental contamination of surfaces by VRE. RESULTS: VRE was detected from 13 (18%) of 74 patients and 32 (10%) of 319 surfaces. The frequency of positive environmental cultures varied by location; cultures were more likely to be positive in patient rooms (15%), followed by common areas on patient floors (9%) and common areas separate from patient floors (1.3%). Surfaces were more likely to be positive in rooms with a VRE-colonized patient (24%), compared with rooms in which patient colonization status was unknown (13%, P=.13) or the patient was not colonized (0%, P=.002). Surfaces were more likely to be contaminated in a room that housed an incontinent compared with continent patients (22% vs 7%, P=.01). CONCLUSIONS: Although environmental contamination by VRE was common in patient rooms, contamination of common-use areas separate from patient floors was infrequent. Despite use of common-use areas by colonized patients, isolation practices at this facility appear to have minimized environmental surface contamination in these areas.