Antibiotic-resistant bloodstream infections in hospitalized patients: specific risk factors in a high-risk population?

BACKGROUND: The aim of this study was to explore characteristics that are associated with bloodstream infections due to specific multiresistant microorganisms (methicillinresitant Staphylococcus aureus, MRSA; vancomycin-resistant enterococci, VRE; third-generation cephalosporin-resistant Enterobacteriaceae) or Candida spp. in hospitalized patients. PATIENTS AND METHODS: All patients who experienced a bloodstream infection with one of the aforementioned pathogens between September 1999 and October 2001 were included into a statistical analysis of independent risk factors. The possible impact of previous antibiotic and antifungal therapies was evaluated.
RESULTS: Of the study population, 22% had two or more episodes with different pathogens. In the 314 patients with a single bloodstream infection MRSA was isolated in 189 patients, VRE in 31, Enterobacteriaceae in 13, and Candida spp. in 80 patients. Crude mortality was high in the study population (overall 40%) and varied between 33% (MRSA bacteremia only) and 58% (VRE bacteremia only). Patients who yielded more than one of the pathogens under surveillance had crude mortalities ranging from 41% to 83% (all four pathogens). In this group of high-risk patients, the following factors were independently associated with the individual pathogen: prior chemotherapy (OR 4.88 CI(95) 1.50-15.87) and bronchoscopy (OR 3.17 CI(95) 1.05-9.52) for VRE patients; burns (OR 4.50 CI(95) 0.90-22.73), presence of a tracheostomy (OR 4.22 CI(95) 1.15-15.38) and acute dialysis (OR 3.62 CI(95) 0.99-13.16) for patients with Enterobacteriaceae; and an underlying malignant disease (OR 1.98 CI95 0.99-3.97), performance of a bowel endoscopy (OR 2.80 CI(95) 1.27-6.13) and presence of a central venous catheter (CVC) (OR 12.34 CI(95) 1.63-90.91) for patients with candidemia.
CONCLUSION: Patients with bacteremia due to VRE, Enterobacteriaceae or Candida spp. had more severe risk factors associated with the respective pathogen than patients with MRSA bacteremia.