Longitudinal Assessment of Multidrug-Resistant Organisms in Newly Admitted Nursing Facility Patients: Implications for an Evolving Population

Abstract

Background: The spread of multidrug-resistant organisms (MDROs) is a global concern, and much about transmission in healthcare systems remains unknown. To reduce hospital stays, nursing facilities (NFs) have increasingly assumed care of post-acute populations. We estimate the prevalence of MDRO colonization in NF patients on enrollment and discharge to community settings, risk factors for colonization, and rates of acquiring MDROs during the stay.

Methods: We conducted a prospective, longitudinal cohort study of newly admitted patients in 6 NFs in southeast Michigan using active microbial surveillance of multiple anatomic sites sampled at enrollment, days 14 and 30, and monthly thereafter for up to 6 months.

Results: We enrolled 651 patients and collected 7526 samples over 1629 visits, with an average of 29 days of follow-up per participant. Nearly all participants were admitted for post-acute care (95%). More than half (56.8%) were colonized with MDROs at enrollment: methicillin-resistant Staphylococcus aureus (MRSA), 16.1%; vancomycin-resistant enterococci (VRE), 33.2%; and resistant gram-negative bacilli (R-GNB), 32.0%. Risk factors for colonization at enrollment included prolonged hospitalization (>14 days), functional disability, antibiotic use, or device use. Rates per 1000 patient-days of acquiring a new MDRO were MRSA, 3.4; VRE, 8.2; and R-GNB, 13.6. MDRO colonization at discharge was similar to that at enrollment (56.4%): MRSA, 18.4%; VRE, 30.3%; and R-GNB, 33.6%.

Conclusions: Short-stay NF patients exhibit a high prevalence of MDROs near the time of admission, as well as at discharge, and may serve as a reservoir for spread in other healthcare settings. Future interventions to reduce MDROs should specifically target this population.

Figure 1.

Patient enrollment. Flow of data from eligible to final enrolled analytic sample. Among the 456 patients with follow-up, 446 were seen on day 14, 248 on day 30, 96 on day 60, 67 on day 90, 46 on day 120, 39 on day 150, and 36 on day 180. Total days of follow-up for the sample of 456 patients was 18717 days.

Figure 2.

Colonization with multidrug-resistant organisms on enrollment and discharge. A, Bars indicate proportion of patients colonized at enrollment and discharge among all 651 patients enrolled in the study. For those who were discharged after only 1 visit, the enrollment visit is considered in both the enrollment and discharge samples. The capped error bars indicate 95% confidence interval (CI). B, Bars and 95% CI error bars indicate proportion of patients colonized at enrollment and discharge, but among only those patients with >1 visit, allowing distinct admission and discharge samples (n = 456). Abbreviations: MDRO, multidrug-resistant organism; MRSA, methicillin-resistant Staphylococcus aureus; R-GNB, resistant gram-negative bacilli; VRE, vancomycin-resistant enterococci.

Figure 3.

Colonization at sampled body sites on enrollment. Circles representing each body site are sized and shaded proportionately to colonization prevalence at that body site, using a multiplier of 1.5 to determine diameter and color saturation.

Figure 4.

Longitudinal changes in multidrug-resistant organism colonization status. Each “n” indicates the number of patients with a given colonization status on study enrollment. Arrow bars indicate patients’ colonization status change from admission to discharge. For example, 70 patients who had multiple visits were colonized with methicillin-resistant Staphylococcus aureus at enrollment. Of those, 64.3% (n = 45) remained colonized at discharge, represented by the top horizontal arrow. The remaining 37.5% (n = 25) spontaneously decolonized and clear on discharge, represented by the arrow originating in the top left corner (colonized, enrollment) and terminating in the bottom right (not colonized, discharge). Abbreviations: MDRO, multidrug-resistant organism; MRSA, methicillin-resistant Staphylococcus aureus; R-GNB, resistant gram-negative bacilli; VRE, vancomycin-resistant enterococci.