Multidrug-resistant Acinetobacter baumannii: an emerging pathogen among older adults in community hospitals and nursing homes

Abstract

Background: Drug-resistant Acinetobacter species are problematic in tertiary-care hospitals. We describe the epidemiology, resistance patterns, and outcomes of older adults with Acinetobacter infection in community hospitals.

Methods: We queried the microbiology databases of the Oakwood Healthcare System (4 hospitals with 632, 259, 199, and 168 beds) for clinical Acinetobacter cultures obtained in 2003-2008. Patients aged 60 years who were admitted from home or nursing homes were included. We recorded the initial Acinetobacter isolate and susceptibility to 8 antibiotics. Cultures obtained 48 h after hospitalization were categorized as "nosocomial." Administrative databases provided patients' origins (home or nursing home) and discharge destinations (home, nursing home, long-term acute-care facility, another hospital, or hospice care or death).

Results: During the 6-year period, 560 community-dwelling (mean age +/- standard deviation, 74 +/- 8.6 years) and 280 nursing home-dwelling (78 +/- 9.1 years) patients had Acinetobacter isolated. During this period, Acinetobacter prevalence increased 25% (P<.001, by trend test). In comparison of 2003 with 2008, Acinetobacter resistance to imipenem and ampicillin/sulbactam increased (from 1.8% to 33.1%; P<.001), as did "panresistance" (ie, resistance to all 8 antibiotics; increase from 0.0% to 13.6%; P<.001). Although resistance was stable in community-acquired isolates (resistance to approximately 4.2 antibiotics), resistance increased among nursing home-acquired and nosocomial-acquired isolates (from 4.5 to 5.7 and from 5.0 to 6.0 antibiotics, respectively; P<.01). At discharge, only 25% of community-dwelling and 50% of nursing home-dwelling patients returned to their place of origin; the remainder required higher levels of care or died. After adjustment for age, length of stay, and origin, resistance to each additional antibiotic predicted a >20% increased risk for discharge to higher levels of care or death (odds ratio, 1.23; 95% confidence interval, 1.11-1.36).

Conclusions: The prevalence and resistance of Acinetobacter species are increasing in the community. Patients with resistant isolates are selectively discharged to nursing homes and long-term acute-care facilities, introducing resistance to new facilities.