Magnitude of bacteraemia is associated with increased mortality in non-typhoid salmonellosis: a one-year follow-up study.

We examined whether the number of positive bottles in a routinely used three-bottle blood culture (BC) set predicted one-year mortality in adult patients with non-typhoid Salmonella (NTS). Data from 1994 through 2003 in North Jutland County, Denmark, were retrieved from health databases and medical records. We used the number of positive BC bottles as an index of magnitude of NTS bacteraemia: Index 0 (reference) patients had a negative BC coincident with an NTS-positive faecal culture and index 1, 2, or 3 patients had increasing levels of NTS bacteraemia. For all patients and for patients with gastroenteritis we computed Kaplan-Meier curves to summarize survival over time and Cox regression analysis to estimate mortality in crude analyses and in analyses adjusted for comorbidity and age. There were 115, 43, 21, and 41 patients with index 0, 1, 2, and 3, respectively. One-year cumulative mortality was 4.4%, 14.0%, 28.6%, and 41.5% for indices 0 to 3. Adjusted one-year mortality rate ratios (with 95% confidence intervals) were 1.7 (0.5-5.8), 5.2 (1.5-17.4), and 5.3 (1.9-14.9) for index 1, 2, and 3 patients, respectively. These estimates remained robust for patients with gastroenteritis. We conclude that higher magnitude of bacteraemia predicted one-year mortality in NTS patients.