Clinical characteristics, treatment and outcomes of MRSA bacteraemia in the elderly

Objectives: To compare clinical and microbiological characteristics, treatment and outcomes of MRSA bacteraemia among elderly and younger patients. Material and methods: Prospective study conducted at 21 Spanish hospitals including patients with MRSA bacteraemia diagnosed between June/2008 and December/2009. Episodes diagnosed in patients aged 75 or more years old (≥75) were compared with the rest of them (<75). Results: Out of 579 episodes of MRSA bacteraemia, 231 (39.9%) occurred in patients ≥75. Comorbidity was significantly higher in older patients (Charlson score ≥4: 52.8 vs. 44%; p = .037) as was the severity of the underlying disease (McCabe ≥1: 61.9 vs. 43.4%; p < .001). In this group the acquisition was more frequently health-care related (43.3 vs. 33.9%, p = .023), mostly from long-term care centers (12.1 vs. 3.7%, p < .001). An unknown focus was more frequent among ≥75 (19.9 vs. 13.8%; p = .050) while severity at presentation was similar between groups (Pitt score ≥3: 31.2 vs. 27.6%; p = .352). The prevalence of vancomycin resistant isolates was similar between groups, as was the appropriateness of empirical antibiotic therapy. Early (EM) and overall mortality (OM) were significantly more frequent in the ≥75 group (EM: 12.1 vs. 6%; p = .010 OM: 42.9 vs. 23%; p < .001). In multivariate analysis age ≥75 was an independent risk factor for overall mortality (aOR: 2.47, CI: 1.63-3.74; p < .001). Conclusion: MRSA bacteraemia was frequent in patients aged ≥75 of our cohort. This group had higher comorbidity rates and the source of infection was more likely to be unknown. Although no differences were seen in severity or adequacy of empiric therapy, elderly patients showed a higher overall mortality.