A case of bloodstream infection caused by Ruminococcus gnavus without gastrointestinal involvement

We report a case of bloodstream infection due to Ruminococcus gnavus (R. gnavus) associated with pelvic abscess in a 74-year-old female patient undergoing radiotherapy for cervical cancer. Gram staining of positive anaerobic blood cultures revealed short chains of gram-positive cocci. Matrixassisted laser desorption ionization time-of-flight mass spectrometry was performed directly on the blood culture bottle, and 16S rRNA sequencing identified the bacterium as R. gnavus. There was no leakage from the sigmoid colon to rectum on enterography, and R. gnavus was not found in the culture of her pelvic abscess. After the administration of piperacillin/tazobactam, her condition markedly improved. This patient with R. gnavus infection demonstrated no gastrointestinal involvement, whereas past published cases reported diverticulitis or intestinal damage. It is possible that bacterial translocation of R. gnavus occurred from the gut microbiota, due to damage to the intestinal tract caused by radiation.

Automated summary

We present a case of bloodstream infection caused by Ruminococcus gnavus (R. gnavus) in a 74-year-old female undergoing radiotherapy for cervical cancer, with pelvic abscess. The identification of the bacterium was confirmed through matrix-assisted laser desorption ionization time-of-flight mass spectrometry and 16S rRNA sequencing. The patient did not show gastrointestinal involvement, contrary to previous cases reporting diverticulitis or intestinal damage, suggesting a possible bacterial translocation from the gut microbiota due to radiation-induced intestinal tract damage.