Bloodstream infections in a geriatric cohort: a population-based study.

PURPOSE: Health care-associated infections are those that do not meet the definition of nosocomial but are acquired by patients with extensive exposure to the health care system placing them at higher risk for resistant organisms. This category is particularly common among elderly patients. The objective of this study was to describe and compare the epidemiologic characteristics of community-acquired, health care-associated and nosocomial bloodstream infections in a geriatric population.
METHODS: A population-based, retrospective study of all patients aged 65 years or greater with positive blood cultures (n=636) identified between January 1, 2003 and December 31, 2005 in Olmsted County, Minnesota. Exposures and clinical information were ascertained through complete chart review, utilizing the resources of the Rochester Epidemiology Project. A total of 347 incident patients with bloodstream infection were identified. Bloodstream infections were described as community-acquired, health care-associated or nosocomial using standardized definitions. Variables analyzed included source, isolate, risk factors, and mortality.
RESULTS: The distribution of bloodstream infection cases that were community-acquired, health care-associated, and nosocomial was 159 (46%), 151 (44%), and 37 (10%), respectively. The prevalence of methicillin-resistant Staphylococcus aureus among S. aureus isolates was 54% and 44% for health care-associated and nosocomial cases, respectively. Fourteen-day mortality among bloodstream infection cases was the same in health care-associated and nosocomial infections (15% vs 14%), and was less in community-acquired (6%) cases (P=.04).
CONCLUSIONS: The category of health care-associated infection identified a unique group of geriatric patients at increased risk of methicillin-resistant Staphylococcus aureus infection and with increased mortality.