Persistent Bacteremia Due to Brevibacterium Species in an Immunocompromised Patient

Nonfermenting coryneform bacteria identified as Brevibacterium species that are isolated from clinical specimens are usually considered to be contaminants from the skin flora. Their clinical significance has rarely been reported, partially because it remains difficult to reliably identify Brevibacterium species (these species are frequently misidentified as Corynebacterium species). Nevertheless, biochemical identification with use of the API-Coryne gallery (bioMerieux, Marcy l'Etoile, France) combined with three additional tests (degradation of tyrosine and xanthine and hydrolysis of casein) can be useful for rapid differentiation between Brevibacterium and other related genera (Corynebacterium and Rhodococcus). Definite identification of such strains requires the use of chemotaxonomic markers such as chromatographic analyses of the cell wall for the presence of meso-diaminopimelic acid in the peptidoglycan, absence of arabinose and mycolic acids, and the presence of major amounts of dihydrogenated menaquinones with eight isoprene units. We describe an immunocompromised patient with persistent bacteremia due to Brevibacterium species. The strain was identified with use of the API-Coryne strip as Rhodococcus equi (83.7% identification [id]). Brevibacterium species (14.6% id), or Corynebacterium group B (1.3% id). The results of the three additional tests were consistent with the presence of Brevibacterium, and definite identification was made with use of complementary chemotaxonomic characters.