Magnitude of bacteraemia is a predictor of mortality during 1 year of follow-up.

We evaluated magnitude of bacteraemia as a predictor of mortality, comprising all adult patients with a first-time mono-microbial bacteraemia. The number of positive bottles [1 (reference), 2, or 3] in the first positive blood culture (BC) was an index of magnitude of bacteraemia. We used Cox's regression analysis to determine age and comorbidity adjusted risk of mortality at days 0-7, 8-30, and 31-365. Of 6406 patients, 31.1% had BC index 1 (BCI 1), 18.3% BCI 2, and 50.6% BCI 3. BCI 3 patients had increased risk of mortality for days 0-7 (1.30, 95% CI 1.10-1.55) and days 8-30 (1.37, 95% CI 1.12-1.68), but not thereafter. However, in surgical patients mortality increased only beyond day 7 (8-30 days: 2.04, 95% CI 1.25-3.33; 31-365 days: 1.27, 95% CI 0.98-1.65). Thus, high magnitude of bacteraemia predicted mortality during the first month with a shift towards long-term mortality in surgical patients.