Publications

Abstract : Background and objectives: Multidrug-resistant gram-negative bacteria are rapidly spreading throughout the world. The epidemiology of multidrug-resistant gram-negative bacteria in patients who require chronic hemodialysis has not been previously studied. Design, setting, participants, & measurements: A prospective cohort study of an outpatient hemodialysis unit was conducted. Serial surveillance cultures for multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus were collected from patients who were undergoing chronic hemodialysis. Results: Nineteen (28%) of the 67 enrolled patients were colonized with one or more antimicrobial-resistant bacteria at study enrollment. Eleven (16%), nine (13%), and three (5%) patients were colonized with multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus, respectively. Independent risk factors associated with harboring multidrug-resistant gram-negative bacteria at enrollment were residence in a long-term care facility and antibiotic exposure for ≥7 d in the previous 3 mo. Twenty-two (40%) of 55 patients who had follow-up cultures acquired at least one antimicrobial-resistant bacterium. A total of 20, 15, and 13% of patients acquired multidrug-resistant gram-negative bacteria, vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureus, respectively. Antibiotic exposure was the only independent risk factor for multidrug-resistant gram-negative bacteria acquisition. Endogenous multidrug-resistant gram-negative bacteria acquisition was detected among 69% of acquired multidrug-resistant gram-negative bacterial strains. Conclusions: The prevalence and acquisition of multidrug-resistant gram-negative bacteria surpassed that of vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus. Endogenous acquisition, as opposed to patient-to-patient spread, was the predominant mechanism of acquisition. Residence in a long-term care facility and antibiotic exposure may be important factors promoting the spread of multidrug-resistant gram-negative bacteria among this patient population. Rates of antibiotic-resistant bacteria are among the highest in patients who require chronic hemodialysis (1). Vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) are among the antimicrobial-resistant bacteria that have been intensely investigated in this patient population (1–3). In the past few years, however, a concerning increase in the prevalence of infections caused by multidrug-resistant gram-negative bacteria (MDRGN) has been documented in other patient populations (4–6). Infections that are caused by these MDRGN are associated with up to five times higher mortality rates compared with infections that are caused by susceptible gram-negative bacteria (7). Among chronic hemodialysis patients, approximately 25% of blood stream infections are caused by gram-negative bacteria (8), and this percentage is increasing steadily (9). Despite these rising rates, antimicrobial resistance among gram-negative bacteria has not been previously investigated in the population of those who undergo chronic hemodialysis. A prospective surveillance study was therefore performed to describe the clinical epidemiology of MDRGN among patients who require chronic hemodialysis. The goals of this study were (1) to determine the percentage of chronic hemodialysis patients who are colonized with MDRGN and compare these rates with VRE and MRSA colonization, (2) to identify the risk factors that are associated with MDRGN colonization, and (3) to determine the mechanism of MDRGN acquisition. For achieving these goals, cultures were obtained at three intervals from patients who were receiving chronic hemodialysis at an outpatient unit to determine whether they were colonized with MDRGN, VRE, or MRSA at enrollment and whether they acquired these antimicrobial-resistant bacteria over time. To understand the transmission dynamics of these antimicrobial-resistant bacteria and identify clonal spread, we performed DNA fingerprinting using pulsed-field gel electrophoresis (PFGE).