Ruminococcus gnavus bacteraemia showing morphological diversity on Gram staining: a case report and literature review

Access Microbiol. 2023 Jun 22;5(6):acmi000442. doi: 10.1099/acmi.0.000442. eCollection 2023.


Ruminococcus gnavus , a Gram-positive anaerobic coccus, is a common constituent of the human gut microbiota but rarely causes any disease in humans. Herein, we report a case of R. gnavus bacteraemia in an immunocompromised 73-year-old man with sigmoid colon perforation. R. gnavus is usually reported as Gram-positive diplococci or short chains on Gram staining; however, in our patient, a blood isolate showed Gram-positive cocci in long chains, and organisms from an anaerobic subculture showed morphological diversity. This case provides insight into the morphological diversity of R. gnavus , which might help with the recognition of these bacteria in the preliminary identification stage on Gram staining.

Keywords: Gram staining; Ruminococcus gnavus; bacteraemia; matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Publication types

  • Case Reports