First case of a bloodstream infection caused by the genus Brachybacterium.

An 83-year-old previously self-sufficient man was referred to our hospital for a fever, severe tenderness over the lumbar spine, and elevated C-reactive protein levels. Computed tomography revealed fluid collection in the intervertebral space of L3/4. Gram-positive, short rod-shaped bacteria were isolated from two sets of blood cultures. A 16S rRNA sequence analysis of an isolate showed a similarity of 98.1% to the nearest type strain Brachybacterium squillarum JCM 16464. Biochemical characteristics of the presently isolated strain differed from those of the most closely related species of the genus Brachybacterium. The patient was successfully discharged on day 73 of admission with antimicrobial therapies and showed no recurrence during outpatient visits. Brachybacterium spp. have mainly been isolated from the environment, and human Brachybacterium infections have rarely been documented to date. To our knowledge, this is the first clinical isolation of Brachybacterium sp. as a causative pathogen of bloodstream infection.