Multi-year comparison of VITEK® MS and 16S rRNA gene sequencing performance for the identification of rarely encountered anaerobes causing invasive human infections in a large Canadian region: can our laboratory abandon 16S rRNA gene sequencing?

Clinical and microbiological characteristics of Ruminococcus gnavus bacteremia and intra-abdominal infection

OBJECTIVES

Ruminococcus gnavus is a rare human pathogen, and clinical data on R. gnavus infection are insufficient. This retrospective study aimed to investigate the clinical characteristics of R. gnavus infections.

METHODS

This study included 13 cases of bacteremia and three cases of non-bacteremia infections caused by R. gnavus. We evaluated the patient data, infection source, clinical outcomes, and antimicrobial susceptibility of R. gnavus isolates for these cases.

RESULTS

The median age of patients was 75 years (range 47-95), and eight patients were female. Twelve cases were presumed to have an intra-abdominal infection source, and the remaining four cases had an unknown infection source. The most common underlying conditions were immunosuppression (seven cases), solid tumors (seven cases), and history of gastrointestinal surgery (five cases). Thirteen patients exhibited gastrointestinal problems (dysfunction, bleeding, intra-abdominal infection, or inflammation). Multiple pathogens were observed in six cases, and fatal outcomes were recorded in three cases. Antimicrobial susceptibility data were available for eight isolates, all of which exhibited low minimum inhibitory concentrations to penicillin (≤0.03 μg/mL), ampicillin-sulbactam (≤0.5 μg/mL), piperacillin-tazobactam (≤4 μg/mL), and metronidazole (≤0.5-1 μg/mL).

CONCLUSION

Ruminococcus gnavus is frequently associated with an intra-abdominal infection source, and treatment strategies should consider the possibility of multiple pathogens.