Invasive infections with Fusobacterium necrophorum including Lemierre's syndrome: an 8-year Swedish nationwide retrospective study

Objectives: We aimed to evaluate the nationwide incidence and a potential increase in invasive infections with Fusobacterium necrophorum. Secondly, we aimed to describe epidemiology, clinical characteristics and outcomes for the different presentations: Lemierre's syndrome (LS), invasive head and neck-infection without LS and invasive non-head and neck-infection. Methods: A retrospective multicentric population-based study of all invasive infections with F. necrophorum diagnosed in Sweden from 2010 to 2017 with 6 months of follow-up was performed through reviews of medical records. Invasive infections were defined and identified by a positive blood culture or sequencing of 16S rDNA, targeted PCR or culture from normally sterile sites. Incidence calculations were performed, including comparisons between 2010-13 and 2014-17, age groups and clinical presentations. Patient and infection characteristics, treatment and clinical outcomes were analysed. Results: Invasive infections with F. necrophorum were diagnosed in 300 cases in Sweden 2010-17. The incidence increased from 2.9 to 5.0 cases/million/year from 2010-13 to 2014-17 (p 0.001). A total of 104/300 (35%) patients developed LS, 102/300 (34%) invasive head and neck infection without LS and 94/300 (31%) invasive non-head and neck infection. The median age was 20, 25 and 64 years, respectively. Among patients with LS 72/96 (75%) had thrombocytopenia on admission, 86/104 (83%) had sepsis, 19/104 (18%) developed septic shock and 45/104 (43%) needed intensive care. 30-day mortality in LS was 2/104 (2%). Conclusion: We describe an increased incidence of invasive infections with F. necrophorum in Sweden and highlight its full spectrum of invasive clinical presentations. LS, in particular, causes considerable morbidity in young and previously healthy patients. (C) 2019 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.