Francisella tularensis infection: variable clinical aspects with persistent pulmonary nodules presentation, a case series of human tularemia in Franche-Comté, France

Abstract

Tularemia is a zoonotic infectious disease caused by the facultative intracellular Gram-negative bacterium Francisella tularensis. Depending on the transmission route of this agent tularemia can present itself as a local infection or a systemic disease. We describe herein three cases of confirmed tularemia in immunocompetent patients during the summer of 2019; two patients with unusual respiratory presentation and pulmonary nodules on imaging, following exposure to aerosols. The third patient was a hunter presenting with a classical ulceroglandular form occurring 4 days after a tick bite in Bourgogne Franche-Comté. All patients were diagnosed from the results of positive F. tularensis PCR (or universal PCR targeting the 16S ribosomal ribonucleic acid gene) and/or seroconversion. The patient with ulceroglandular form received antibiotics, with a complete recovery. The two patients with pneumonic tularemia recovered without antibiotic treatment. However, pulmonary nodules persisted on follow-up CT months later, despite overall clinical recovery.

Keywords: Diagnosis; Exposure; Franche-Comté; Francisella tularensis; Polymerase Chain Reaction; Serology; Tick bite; Tularemia.