Room Assignment and VRE Transmission

Abstract & Commentary

Synopsis: Among all factors associated with VRE transmission, VRE acquisition may depend on room contamination, even after extensive cleaning.

Source: Martinez JA, et al. Role of environmental contamination as a risk factor for acquisition of vancomycin-resistant enterococci in patients treated in a medical intensive care unit. Arch Intern Med. 2003;163(16):1905-1912.

The recent emergence and spread of vancomycin-resistant enterococci (VRE) is one of the most important issues in critical care today. This study was conducted to further define risk factors for VRE acquisition in the ICU setting, including the role of room contamination. The setting was a 10-bed MICU in a university-affiliated hospital that had implemented active surveillance monitoring for VRE colonization, but continued to experience a high number of VRE cases, of which 80% were believed to be hospital-acquired. Per the surveillance protocol, a rectal swab was to be obtained from all patients within 48 hours of admission and weekly as long as findings of previous cultures remained negative and the patient remained in the unit. Hospital isolation precautions included placing infected patients in a private room, gown and gloves for all room entries, and hand washing with antiseptic soap. Acquisition of VRE was defined as absence of clinical samples positive for VRE at MICU admission, a negative first-rectal culture, and any positive findings at follow-up (after 48 hours).

During the study period, there were 365 admissions, and 169 (46%) underwent screening for VRE colonization. Of these, 31 (23%) acquired VRE during their MICU stay and were termed cases. Two controls were identified for each of 30 of the cases, and these 90 subjects (60 controls, 30 cases) were subjects for the study. The remaining case was not included because an appropriate control could not be identified.

Using multivariate logistic regression, 4 variables were identified as the best independent predictors associated with VRE acquisition: administration of vancomycin before or after MICU admission (P = 0.03); having received quinolones before MICU admission (P = 0.03); a stay of longer than 1 week in the hospital before transfer to the MICU (P = 0.04); and location in a high-risk room (P = 0.02). Rooms designated as high risk (2/10) had a variety of contaminated surfaces, including a light switch, toilet flusher, telephone handle, bathroom faucet, and IV pumps.

Comment by Leslie A. Hoffman, PhD, RN

In this study, length of hospital stay before MICU admission, use of quinolones before MICU admission, use of vancomycin before or during MICU admission, and placement in a particular room were the most important predictors for VRE transmission. It is well known that many surfaces in rooms of infected or colonized patients can become contaminated. However, it has been difficult to confirm that surface contamination is an important factor in VRE transmission. Since their first appearance in 1988, VRE have become endemic in many hospitals. Data supporting the use of contact precautions are mixed, with some studies reporting benefits while others do not.

Findings of the present study may be a partial explanation for these conflicting findings. If VRE infection results from suboptimal room cleaning, isolation procedures would not have an effect. Findings of the present study also provide additional support for the role of exposure to antibiotics as a risk factor for VRE acquisition. Two significant risk factors involved administration of quinolones before MICU admission and IV vancomycin at any time before or after MICU admission. This finding suggests that antibiotic restriction policies in settings such as the ICU, where many patients receive antibiotics prior to unit admission, might be less effective than expected since risk was incurred prior to unit admission.

This study had several limitations. The sample size was moderate and data were collected retrospectively. In addition, less than half (46%) of the patients had complete data for all parts of the surveillance monitoring protocol in terms of obtaining a rectal culture within 48 hours of admission and weekly thereafter until unit discharge. Consequently, some patients may have been colonized at admission but not identified. Nevertheless, failure to identify such patients would be unlikely to influence the association with VRE acquisition and admission to a specific room. An easily modifiable risk factor, room contamination deserves greater scrutiny as a variable that increases risk for VRE acquisition. The cleaning procedure used was standard (phenolic disinfectant on all room surfaces, cleaning for 20-30 minutes), but obviously inadequate. Of note, in an attempt to eliminate environmental contamination as a risk factor, the unit instituted a policy of cleaning rooms in a more thorough manner that took approximately 4 hours to complete. After this change, no environmental samples (10 per room) were positive for VRE.

Dr. Hoffman, Department of Acute/Tertiary Care School of Nursing University of Pittsburgh