infection control & hospital epidemiology october 2015, vol. 36, no. 10 original article
Prevalence of and Risk Factors for Multidrug-Resistant Acinetobacter baumannii Colonization Among High-Risk Nursing Home Residents
Lona Mody, MD, MSc;1,2 Kristen E. Gibson, MPH;1 Amanda Horcher, MPH;3 Katherine Prenovost, PhD;4
Sara E. McNamara, MPH, MT(ASCP);1 Betsy Foxman, PhD;3 Keith S. Kaye, MD, MPH;5 Suzanne Bradley, MD;6 on behalf of the Targeted Infection Prevention Study Team, Ann Arbor, Michigan
objective. To characterize the epidemiology of multidrug-resistant (MDR) Acinetobacter baumannii colonization in high-risk nursing home (NH) residents.
design. Nested case-control study within a multicenter prospective intervention trial. setting. Four NHs in Southeast Michigan.
participants. Case patients and control subjects were NH residents with an indwelling device (urinary catheter and/or feeding tube) selected from the control arm of the Targeted Infection Prevention study. Cases were residents colonized with MDR (resistant to ≥3 classes of antibiotics) A. baumannii; controls were never colonized with MDR A. baumannii.
methods. For active surveillance cultures, specimens from the nares, oropharynx, groin, perianal area, wounds, and device insertion site(s) were collected upon study enrollment, day 14, and monthly thereafter. A. baumannii strains and their susceptibilities were identified using standard microbiologic methods.
results. Of 168 NH residents, 25 (15%) were colonized with MDR A. baumannii. Compared with the 143 controls, cases were more functionally disabled (Physical Self-Maintenance Score >24; odds ratio, 5.1 [95% CI, 1.8–14.9]; P<.004), colonized with Proteus mirabilis (5.8 [1.9–17.9]; P<.003), and diabetic (3.4 [1.2–9.9]; P<.03). Most cases (22 [88%]) were colonized with multiple antibiotic-resistant organisms and 16 (64%) exhibited co-colonization with at least one other resistant gram-negative bacteria.
conclusion. Functional disability, P. mirabilis colonization, and diabetes mellitus are important risk factors for colonization with MDR A. baumannii in high-risk NH residents. A. baumannii exhibits widespread antibiotic resistance and a preference to colonize with other antibiotic-resistant organisms, meriting enhanced attention and improved infection control practices in these residents.
Infect. Control Hosp. Epidemiol. 2015;36(10):1155–1162
Acinetobacter baumannii is a gram-negative bacterium that causes a wide range of monomicrobial and polymicrobial infections, including bacteremia, pneumonia, urinary tract infections, deep wound infections, and osteomyelitis.1–5 One of the largest challenges in treating A. baumannii infec- tions is the organism’s capacity to rapidly acquire antibiotic resistance.1–3,6–12 Pan-resistant A. baumannii isolates have emerged, including isolates resistant to carbapenems, colistin, and polymyxins, rendering these strains virtually untreatable.1,3,6,8,9,12–17 Certain strains of A. baumannii have the ability to form biofilms and persist in the environment,18–20 including on
horizontal surfaces and medical devices such as urinary catheters and intravenous lines, facilitating the organism’s spread from patient to patient via the hands of healthcare workers.10–21 Resistance to disinfectants further contributes to the persistence of the A. baumannii in the environment and the development of endemics and epidemics in long-term and acute care facilities, sometimes requiring the closure of entire wings to contain the outbreaks and stop spread.1,3,6,8,12,15,22,23 Multidrug-resistant (MDR) A. baumannii were initially
confined to acute care hospitals. Recently,MDR A. baumannii has been reported to cause infection among hospitalized older adults in long-term care settings, especially in those with
Affiliations: 1. Division of Geriatric and Palliative Care Medicine, University of Michigan Medical School, Ann Arbor, Michigan; 2. Geriatrics Research
Education and Clinical Center, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan; 3. Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, Michigan; 4. Veterans Affairs Center for Clinical Management Research, Ann Arbor, Michigan; 5. Division of Infectious Diseases, Detroit Medical Center and Wayne State University, Detroit, Michigan; 6. Infectious Diseases Section, Veterans Affairs Ann Arbor Healthcare System and the University of Michigan Medical School, Ann Arbor, Michigan.
© 2015 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2015/3610-0005. DOI: 10.1017/ice.2015.143 Received March 6, 2015; accepted May 6, 2015; electronically published June 15, 2015
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