Multidrug-resistant gram-negative bacteria in a long-term care facility: Prevalence and risk factors

OBJECTIVES: To quantify the prevalence, risk factors, and mode of transmission associated with colonization by multidrug-resistant gram-negative bacteria (MDRGN) in the long-term care (LTC) setting. DESIGN: Cross-sectional. SETTING: Four nursing units in a 648-bed LTC facility in Boston, Massachusetts. PARTICIPANTS: Eighty-four long-term care residents. MEASUREMENTS: Nasal and rectal swabs were obtained to determine colonization with MDRGN; if present, molecular typing was performed. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) was also determined. Demographic and clinical characteristics were obtained from the medical record. Multivariable analysis was used to identify factors independently associated with MDRGN colonization. RESULTS: A total of 51%, 28%, and 4% subjects were colonized with MDRGN, MRSA, and VRE, respectively. After multivariable adjustment, advanced dementia (adjusted odds ratio (AOR)=2.9, 95% confidence interval (CI)=1.2-7.35, P=.02) and nonambulatory status (AOR=5.7, 95% CI=1.1-28.9, P=.04) were the only independent risk factors for harboring MDRGN. Molecular typing indicated person-to-person transmission. CONCLUSION: Colonization with MDRGN is common in the LTC setting. A diagnosis of advanced dementia is a major risk factor for harboring MDRGN.