Bloodstream Infections in the Elderly: Effects of Nursing Homes on Antimicrobial-Resistant Bacteria

Objectives: Emergency room visits by nursing home patients with bloodstream infections (BSIs) are not uncommon and pose challenges to clinicians when selecting appropriate antimicrobial agents. This research aims to discover distinct bacteriology in nursing home patients by focusing particularly on antimicrobial-resistant bacteria. Methods: This retrospective study enrolled patients aged 65 years or older who had documented positive blood culture reports between May 2006 and June 2008. Patients were further categorized into subgroups according to nursing home history and the timely trend of hospital exposure. Results: The adjusted risk of BSIs associated with nursing home exposure was significantly higher in Methicillin-resistant Staphylococcus aureus (odds ratio (OR) 2.0; 95% CI 1.5–2.8), Methicillin-resistant coagulase-negative Staphylococcus species (OR 1.7; 95% CI 1.2–2.5), and Enterobacteriaceae-extended spectrum β-lactamase-producing Enterobacteriaceae (OR 2.4; 95% CI 1.5–3.9), but not in Pseudomonas aeruginosa (OR 1.4; 95% CI 0.9–2.2) or Acinetobacter baumannii (OR 0.9; 95% CI 0.5–1.5). Conclusion: Host environments—nursing home or hospital exposure—were shown to be more significant than medical comorbid conditions for acquiring antimicrobial-resistant pathogens. Each unique environment increased the risk for acquiring some pathogens, but not all. In addition, these environmental factors may also exert cumulative effects toward some specific pathogens