Clostridioides difficile carriage in animals and the associated changes in the host fecal microbiota

The relationship between the gut microbiota and Clostridioides difficile, and its role in the severity of C. difficile infection in humans is an area of active research. Intestinal carriage of toxigenic and non-toxigenic C. difficile strains, with and without clinical signs, is reported in animals, however few studies have looked at the risk factors associated with C. difficile carriage and the role of the host gut microbiota. Here, we isolated and characterized C. difficile strains from different animal species (predominantly canines (dogs), felines (cats), and equines (horses)) that were brought in for tertiary care at North Carolina State University Veterinary Hospital. C. difficile strains were characterized by toxin gene profiling, fluorescent PCR ribotyping, and antimicrobial susceptibility testing. 16S rRNA gene sequencing was done on animal feces to investigate the relationship between the presence of C. difficile and the gut microbiota in different hosts. Here, we show that C. difficile was recovered from 20.9% of samples (42/201), which included 33 canines, 2 felines, and 7 equines. Over 69% (29/42) of the isolates were toxigenic and belonged to 14 different ribotypes including ones known to cause CDI in humans. The presence of C. difficile results in a shift in the fecal microbial community structure in both canines and equines. Commensal Clostridium hiranonis was negatively associated with C. difficile in canines. Further experimentation showed a clear antagonistic relationship between the two strains in vitro, suggesting that commensal Clostridia might play a role in colonization resistance against C. difficile in different hosts.

Chronic opioid use is associated with altered gut microbiota and predicts readmissions in patients with cirrhosis

BACKGROUND

Opioid use is epidemic in cirrhosis, which could precipitate hepatic encephalopathy (HE) potentially through gut dysbiosis and inflammation.

AIM

To define the effect of opioids on readmissions and on gut microbiota composition and functionality.

METHODS

Cohort 1 had 200 cirrhotic in-patients (with/without opioid use) followed prospectively through the index hospitalisation and 6 months post discharge. Readmissions (HE-related/unrelated) were compared between patients discharged on opioids compared to the rest, including using a multi-variable analysis. Cohort 2 consisted of 72 cirrhotics on chronic opioids who were age/model for end-stage liver disease (MELD) and prior HE-balanced with 72 cirrhotics not on opioids. Stool microbiota composition (multi-tagged sequencing), predicted functionality (PiCRUST), endotoxemia and systemic inflammation (IL-6, IL-17) were compared.

RESULTS

Cohort 1: Chronic opioid use was statistically similar between those admitted with/without HE, and was judged to be an HE precipitant in <5% of cases during the index hospitalisation. Of the 144 patients alive at 6 months, 82 were readmitted. The opioid users had a significantly higher all cause (69% vs. 48%, P = 0.008), but not HE-related readmissions (30% vs. 41%, P = 0.30). On regression, opioid therapy and female gender were predictive of readmission independent of MELD score and previous HE. Cohort 2: Significant dysbiosis was noted in the opioid cohort, especially in HE+opioid patients with lower autochthonous taxa and Bacteroidaceae relative abundance. PiCRUST showed highest aromatic amino acid and endotoxin production in opioid users. Opioid users also had higher endotoxemia and IL-6 but not IL-17.

CONCLUSION

Chronic opioid use in cirrhosis is associated with increased endotoxemia, dysbiosis and all-cause readmissions.

HCV eradication does not impact gut dysbiosis or systemic inflammation in cirrhotic patients

BACKGROUND

Eradication of hepatitis C virus (HCV) is increasing but its residual impact on the pro-inflammatory milieu in cirrhosis, which is associated with gut dysbiosis, is unclear.

AIM

To define the impact of sustained virological response (SVR) on gut dysbiosis and systemic inflammation in HCV cirrhosis patients.

METHODS

Cirrhotic out-patients with HCV with/without SVR (achieved >1 year prior) and age-matched healthy controls underwent serum and stool collection. Serum was analysed for IL-6, TNF-α and endotoxin while stool microbiota analysis was performed using multitagged pyrosequencing. Microbial comparisons were made using UNIFRAC and cirrhosis dysbiosis ratio (lower score indicates dysbiosis). Comparisons were performed between cirrhotics with/without SVR and controls vs. cirrhotic patients.

RESULTS

A total of 105 HCV cirrhotics and 45 age-matched healthy controls were enrolled. Twenty-one patients had achieved SVR using pegylated interferon + ribavrin a median of 15 months prior. No significant differences on demographics, cirrhosis severity, concomitant medications or diabetes were seen between cirrhotics with/without SVR. There was no significant difference in overall microbiota composition (UNIFRAC P = 0.3) overall or within specific microbial families (cirrhosis dysbiosis ratio median 1.3 vs. 1.0, P = 0.45) between groups with/without SVR. This also extended towards IL-6, TNF-α and endotoxin levels. Both cirrhosis groups, however, had significant dysbiosis compared to healthy controls [UNIFRAC P = 0.01, cirrhosis dysbiosis ratio (1.1 vs. 2.9, P < 0.001)] along with higher levels of endotoxin, IL-6 and TNF-α.

CONCLUSIONS

Gut dysbiosis and a pro-inflammatory systemic milieu, are found in HCV cirrhosis regardless of SVR. This persistent dysbiosis could contribute towards varying rates of improvement after HCV eradication in cirrhosis.