Eubacterium callanderi bacteremia: A case report

Abstract

Eubacterium species are a group of obligated anaerobic gram-positive bacilli that are recognized as commensals of the gastrointestinal tract flora. Cases of bacteremia mediated by Eubacterium are rare. This report describes a case of bacteremia caused by Eubacterium callanderi in an 82-year-old female with a history of a cecal perforation secondary to an obstructing sigmoid stricture. The results showed the utility of using whole genome sequencing to identify the causative agent and underlined the significance to identify anaerobic organisms in diagnostic microbiology practice and to perform antimicrobial susceptibility testing to guide therapy and enhance patient outcomes.

Keywords: Anaerobic bacteremia; Eubacterium callanderi bacteremia.

Fig. 1

(A) Eubacterium callanderi isolated from the patient’s positive blood culture plated on anaerobic blood agar (CDC) incubated anaerobically. (B) Gram stain of Eubacterium callanderi from culture 1000X magnification.

Fig. 2

Phylogenetic analysis of E. callanderi isolate 2 (AR240121, light red). (A) Phylogenetic tree of the case isolate compared to reference genomes of Eubacterium species to include E. maltosivorans, E. limosum and E. callanderi. The case isolate is genetically most closely related to E. callanderi. (B) Phylogenetic tree of the case isolate compared to genomes of E. limosum (highlighted in blue) and E. callanderi (highlighted in green). The case isolate is genetically most closely related to a cluster of E. callanderi strains. Interestingly, another genome (GCA 018363665, is annotated and classified as E. limosum but clustered with the E. callanderi strains. This is likely due to a misannotation since the genus is not well defined and many strains often undergo reassignment.