Spondylodiscitis caused by Citrobacter koseri: a case report

Citrobacter species are ubiquitous environmental gram-negative bacilli that rarely cause severe infections in immunocompetent adults. Spondylodiscitis caused by Citrobacter koseri is an exceptionally rare clinical entity, with fewer than 15 cases reported in the literature. We report a case of community-acquired Citrobacter koseri spondylodiscitis to highlight the diagnostic and therapeutic management of this unusual pathogen.

A 77-year-old Tunisian woman presented with acute inflammatory dorsal back pain and fever. Laboratory evaluation revealed elevated inflammatory markers. Magnetic resonance imaging (MRI) of the spine demonstrated spondylodiscitis at the T9-T10 level with associated non-compressive epiduritis and paravertebral soft tissue phlegmon. Screening for common infectious foci, including urine cultures and echocardiography, was negative. Blood cultures and a computed tomography (CT)-guided disco-vertebral biopsy both isolated Citrobacter koseri. The patient was successfully treated with a specific antibiotic regimen comprising intravenous ceftazidime and ciprofloxacin for 3 weeks, followed by oral ciprofloxacin and trimethoprim-sulfamethoxazole for a total duration of 3 months. At the 3-month follow-up, the patient had achieved a complete clinical and biological recovery.

This case underscores that Citrobacter koseri can cause spontaneous bacterial spondylodiscitis even in elderly patients from the community with no identifiable urinary or biliary infection. It highlights the importance of definitive microbiological diagnosis via biopsy or blood culture to guide targeted antibiotic therapy. Conservative management with prolonged fluoroquinolone-based regimens can lead to excellent outcomes in patients without neurological deficits.