Serratia Bacteraemia in the North Denmark Region: A Population-Based Study (2010-2024).

Population-based data on Serratia bacteraemia are limited. We conducted a population-based cohort study of patients with a first-time episode of Serratia bacteraemia in the North Denmark Region between 1 January 2010 and 30 June 2024 (catchment population ~590,000). Clinical and microbiological data were obtained from medical records and the regional microbiological database. A total of 188 patients were identified. The median age was 70 years (IQR 60-78), 66% were male and 48% had a high Charlson Comorbidity Index score (≥ 3). The annual incidence remained stable at 2.1 per 100,000 person-years (95% CI 1.8-2.5). Bacteraemia was community-acquired in 38% of patients, healthcare-associated in 2% and hospital-acquired in 37%. The most common foci of infection were the urinary tract (25%), hepatobiliary tract (20%) and respiratory tract (14%), while a focus was not identified in 28% of patients. Thirty-day all-cause mortality was 24%. In an exploratory adjusted Poisson regression analysis, increasing age (RR 1.02, 95% CI 1.00-1.05) and high comorbidity (RR 2.58, 95% CI 1.01-6.63) were associated with increased mortality, whereas acquisition was not. Serratia bacteraemia predominantly affected older patients with substantial comorbidity and was associated with considerable mortality. Host-related factors appeared to be important determinants of outcome.