Background: The role of environmental contamination in nosocomial cross-transmission of antibiotic-resistant bacteria has been unresolved. Using vancomycin-resistant enterococci (VRE) as a marker organism, we investigated the effects of improved environmental cleaning with and without promotion of hand hygiene adherence on the spread of VRE in a medical intensive care unit.
Methods: The study comprised a baseline period (period 1), a period of educational intervention to improve environmental cleaning (period 2), a "washout" period without any specific intervention (period 3), and a period of multimodal hand hygiene intervention (period 4). We performed cultures for VRE of rectal swab samples obtained from patients at admission to the intensive care unit and daily thereafter, and we performed cultures of environmental samples and samples from the hands of health care workers twice weekly. We measured patient clinical and demographic variables and monitored intervention adherence frequently.
Results: Our study included 748 admissions to the intensive care unit over a 9-month period. VRE acquisition rates were 33.47 cases per 1000 patient-days at risk for period 1 and 16.84, 12.09, and 10.40 cases per 1000 patient-days at risk for periods 2, 3, and 4, respectively. The mean (+/-SD) weekly rate of environmental sites cleaned increased from 0.48+/-0.08 at baseline to 0.87+/-0.08 in period 2; similarly high cleaning rates persisted in periods 3 and 4. Mean (+/-SD) weekly hand hygiene adherence rate was 0.40+/-0.01 at baseline and increased to 0.57+/-0.11 in period 2, without a specific intervention to improve adherence, but decreased to 0.29+/-0.26 in period 3 and 0.43+/-0.1 in period 4. Mean proportions of positive results of cultures of environmental and hand samples decreased in period 2 and remained low thereafter. In a Cox proportional hazards model, the hazard ratio for acquiring VRE during periods 2-4 was 0.36 (95% confidence interval, 0.19-0.68); the only determinant explaining the difference in VRE acquisition was admission to the intensive care unit during period 1.
Conclusions: Decreasing environmental contamination may help to control the spread of some antibiotic-resistant bacteria in hospitals.