Misidentification of Brevibacterium casei as Propionibacterium acnes Isolated from the Blood of a Patient with Malignant Lymphoma

Brevibacterium spp. are Gram-positive, irregularly rod-shaped, strictly aerobic bacteria that resemble corynebacteria. Since they are a part of normal skin flora, they have been regarded as apathogenic, and human infections related to them are very rare. A 46-year-old man previously diagnosed with diffuse large B-cell lymphoma presented with fever without a definitive infectious source. Blood cultures from both peripheral blood and a central venous catheter showed that only aerobic bottles grew contaminants, while anaerobic bottles did not. Although the automated microbial identification system indicated Propionibacterium acnes, the isolated species was identified as B. casei by 16S rRNA sequence analysis. Our case emphasizes the utilization of 16S rRNA sequence analysis when the result from an automated system does not correspond with other laboratory findings. This is the first case of catheter-related blood stream infection due to B. casei identified by 16S rRNA sequence analysis. (Ann Clin Microbiol 2014;17:95-98)