Unusual Case of Spondylodiscitis due to Listeria monocytogenes

A 92 year-old man was admitted to the emergency unit at Nantes University hospital for fever and acute low back pain since one week associated with a systemic inflammatory response syndrome and oliguria. His medical history included arterial hypertension, heart failure and arrhythmia, gastric ulcer and hip arthroplasty. He did not recall gastrointestinal symptoms or specific trauma to his skin. On admission, he had a temperature of 38.2°C and normal blood pressure. General examination was normal apart from low back pain and paraspinal muscle spasm. He had no sign of meningoencephalitis. Blood tests showed a total white cell count of 7.47 G.L-1 with normal neutrophil count (82.7%) and lymphopenia (7.6%) and an elevated C-reactive protein level of 190.8 mg.L-1. Three aerobic and anaerobic blood cultures (Bactec FX, Becton, Dickinson, Sparks, MD, USA) were performed on the peripheral site over the course of 24 h. The two first aerobic blood cultures were positive after 22h of incubation and yielded Gram-positive bacilli. The etiological agent of this bacteremia was identified as Listeria monocytogenes only one hour later after the Gram staining thanks to a modified driven hemolysis method using MALDI-TOF mass spectrometry [1]. After 24h of incubation, the bacterial identification was confirmed by using the hemolytic colony on blood agar plate (bioMerieux, Marcy l’Etoile, France). Esculine test was rapidly positive. According to French Listeria National center, multiplex PCR showed that this strain belonged to the serotype-associated group 4b complex (serotypes 4b, 4d, and 4e). Despite recommendations in invasive listeriosis, lumbar puncture (to objective paucisymptomatic meningoencephalitis) was not achieved in this case given the patient’s age and location of infection [2]. Two days after admission, magnetic resonance imaging of the lumbar spine revealed a multifocal spondylodiscitis with global (L4-L5) and focal (L3-L4 and L5-S1) hyper intensity of the discus in T2 and abnormal hypo-intensity of the adjacent plate of the L3–L4 discus on T1 (Fig. 1). Transthoracic echocardiography did not found any evidence for infective endocarditis. Antibiotic therapy with continuous intravenous amoxicillin (200 mg/kg daily) during six days and gentamicin (5 mg/kg in one daily injection) during four days was started. In vitro susceptibility testing was performed using the Ivyspring