Incidence and prognosis of nontyphoid Salmonella bacteraemia in Denmark:: a 10-year county-based follow-up study

The aim of this study was to examine the incidence and prognosis of nontyphoid Salmonella bacteraemia in a well-defined population in which complete follow-up investigations had been performed. All patients with nontyphoid Salmonella bacteraemia from 1994 through 2003 in North Jutland County, Denmark, were eligible for the study. Annual incidence rates were calculated for 10-year age groups. The North Jutland County Bacteraemia Database (inclusion of subjects), medical hospital records, the Prescription Registry (redemption of prescription drugs), and the Central Population Registry (deaths) were used as data sources. The outcomes were mortality within 30 and 180 days of the first nontyphoid-Salmonella-positive blood sample. Cox proportional-hazards regression analysis was performed, first with age and comorbidity as evidenced by Charlson index scores, and second with selected clinical and laboratory prognostic variables potentially related to nontyphoid Salmonella bacteraemia per se. A total of 111 non-typhoid Salmonella bacteraemia patients were included in the study. The incidence rate (mean 2.3/100,000 person-years) increased steadily from 1.9/100,000 person-years in the 40-49-year age group to 14.6/100,000 person-years in those > 90 years. Twelve (11%) and 24 (22%) patients died within 30 and 180 days, respectively. Cox regression analyses showed that increasing age and, to a higher degree, increasing levels of comorbidity were independently associated with an unfavourable outcome, whereas none of the clinical or laboratory variables studied were strong independent prognostic factors. In conclusion, the presence of comorbid diseases and old age were independently associated with mortality, whereas clinical and laboratory variables were less important.