Secondary bile salts may be novel biomarkers of C. difficile recurrence
Patients with recurrent Clostridium difficile infection had distinct bile acid and microbiome profiles compared with healthy controls and patients with first Clostridium difficile infection, according to research published in Alimentary Pharmacology and Therapeutics. These findings led researchers to suggest that secondary bile salts may have potential as a novel biomarker for recurrence.
“The mechanism of recurrent CDI remains unknown, though bile salts have been implicated. The intestinal microbiota metabolizes bile acids, a process that if disrupted by antibiotics may be critical to initiation of CDI,” Jessica R. Allegretti, MD, MPH, from the Crohn’s and Colitis Center and Harvard Medical School, Brigham and Women's Hospital told Healio Gastroenterology. “This study aimed to assess bile salt profiles in three distinct groups of patients — recurrent CDI, first episode CDI and healthy controls — to better understand the role bile salts play in pathogenesis of recurrent CDI and to gain further understanding as to which bacteria may be responsible for this important function. Additionally, we performed random forest regression to identify predictors of group membership.”
Jessica R. Allegretti
Allegretti and colleagues collected blood and stool samples from 20 patients with first CDI, 19 patients with recurrent CDI being screened for fecal transplantation, and 21 controls. Samples from the first CDI arm were collected before patients received antibiotic treatment, whereas samples from the recurrent CDI arm were collected while they were receiving stable doses of chronic oral vancomycin. Participants in the control arm had not been exposed to antibiotics for at least 3 months.
Researchers then analyzed blood plasma and stool samples for bile salt metabolomics profiles, and performed 16S rRNA amplicon sequencing to determine the microbiota composition of the stool samples.
“We found that secondary bile acids, which are protective, were significantly elevated in controls compared with both CDI groups in stool and blood,” Allegretti said.
The median secondary bile acids lithocholate and deoxycholate were significantly higher in the stool samples of controls compared with both first CDI (P < .0001 and P = .0003, respectively) and recurrent CDI arms (both P < .0001). Deoxycholate was also significantly higher in first vs. recurrent CDI patients (P = .017).
Median deoxycholic acid was significantly higher in the blood samples of controls compared with both first CDI (P < .0001) and recurrent CDI patients (P = .05), and was also significantly higher in the blood samples of first vs. recurrent CDI patients (P = .003).
“Conversely, primary bile acids, which can induce germination, were elevated in the recurrent group,” Allegretti said.
The primary bile acids cholate and chenodeoxycholate were significantly higher in the stool samples of the recurrent CDI arm compared with controls (P = .0002 and P = .02, respectively).
16S rRNA gene analyses showed significant differences in microbial alpha diversity across groups, which were most pronounced in recurrent CDI patients vs. controls (adjusted P < .001), but also significant between first and recurrent CDI patients and between first CDI patients and controls (both adjusted P < .05). There were also significant differences in beta-diversity between all groups (P = .001) and significant differences in relative abundances at the taxa level.
Using PICRUSt analyses, the researchers also found significant differences in predicted abundances of bacterial bile salt hydrolase genes between groups. Finally, using random forest regression, the researchers differentiated recurrent and first CDI patients 84.2% of the time using bile acid ratios, with stool deoxycholate to glycoursodeoxycholate ratio as the best predictor.
“Plasma deoxycholate (a secondary bile acid) was a strong predictor of disease state and may be utilized as a possible biomarker of recurrence,” Allegretti said. “This study further elucidates the role of bile salts in the pathogenesis of recurrent CDI and identifies possible novel biomarkers for recurrent disease.” – by Adam Leitenberger
Disclosure: The researchers report no relevant financial disclosures.