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

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.