Robinsoniella peoriensis bacteremia in a patient with colorectal cancer: a case report and literature review

Robinsoniella peoriensis, an anaerobic, Gram-positive bacillus within the phylum Firmicutes and family Lachnospiraceae, is a putative commensal anaerobe of the human gut and an infrequent cause of opportunistic infection, including severe bloodstream infections (BSI). We report a case of BSI due to R. peoriensis and analyze its pertinent clinical and microbiological characteristics. The patient was a 71-year-old male who developed BSI secondary to anastomotic leakage following laparoscopic radical resection for rectal adenocarcinoma. Anaerobic blood cultures obtained on postoperative day 4 signaled positive after 96 h of incubation. The isolate was identified as R. peoriensis by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Whole-genome sequencing revealed a notably diverse array of antimicrobial resistance genes, as well as two virulence-associated genes (tufA and groEL). Etest-based antimicrobial susceptibility testing demonstrated susceptibility to vancomycin, piperacillin-tazobactam, meropenem, and imipenem; intermediate resistant to clindamycin; and resistant to penicillin. The infection was effectively controlled after clinicians promptly initiated empirical therapy with meropenem monotherapy, and the patient eventually recovered and was discharged. This case highlights that R. peoriensis infection can be associated with disruption of the intestinal mucosal barrier, as may occur following surgery for malignancy. A marked discordance between the genotypic resistance profile and phenotypic susceptibility was observed, emphasizing the critical role of standardized in vitro susceptibility testing to guide therapy. Carbapenems (e.g., meropenem) represent an effective therapeutic option for such infections. Due to the rarity of Robinsoniella peoriensis infections, our literature review identified only 22 previously documented cases, we aim to provide insights to aid in the diagnosis and treatment of infections caused by this rare pathogen.