Parvimonas micra as a rare cause of spondylodiscitis - case series from a single centre

BACKGROUND: The anaerobe Parvimonas micra is usually recovered as part of the normal flora or in polymicrobial infections of odontogenic or gastrointestinal origin. P. micra has rarely been described as the causative organism of pyogenic spondylodiscitis. Here we report multiple cases of spondylodiscitis caused by this organism and compare their clinical features with the published literature. METHODS: We performed a retrospective review of all institutional cases with P. micra spondylodiscitis between 01 June 2012 and 31 May 2019. For comparison, the literature was searched for studies reporting vertebral infections with P. micra in adult patients. RESULTS: Over 7 years, six cases were identified: one with a polymicrobial infection (with P. micra and Fusobacterium nucleatum) and five with P. micra as the only pathogen isolated. The six patients with P. micra infections were between 63 and 82 years old (median 72 years) and presented with persistent lower back pain. Common findings were infection of the lumbar spine region (in 6/6 cases) and recent dental inflammation (4/6 cases). 3/6 patients had previously undergone decompressive spinal surgery due to spinal stenosis (2 to 11 years before). In 4/6 cases the organism was detected in blood cultures drawn at admission. Treatment consisted of antibiotics for all patients and additional decompressive surgery due to abscess formation in half the cases. Outcomes were mostly favourable, but persistent pain was a common complaint after resolution of infection. CONCLUSIONS: P. micra is a rare cause of spondylodiscitis. Nevertheless, recent dental procedures with subsequent back pain should lead to the consideration of possible anaerobic causes of spondylodiscitis. Heightened awareness of this pathogen and improvements in diagnostic methods might lead to higher detection rates.