Effects of hyperbaric conditions on fecal microbiota

Effects of Hyperbaric Oxygen Therapy for Clostridioides difficile-associated Colitis: A Retrospective Study

Objectives

Clostridioides difficile (CD) is an anaerobic spore-forming Gram-positive rod that is a major cause of antibiotic-associated diarrhea. Hyperbaric oxygen therapy (HBO) is a well-established treatment for Clostridium perfringens, but there are no reports that have examined the efficacy of HBO against CD, which is also an anaerobic bacterium.

Methods

In this study, we retrospectively examined whether HBO therapy affects the prognosis following CD infections (CDI). This study included 92 inpatients diagnosed with CDI at our hospital between January 2013 and December 2022. Of these, 16 patients received HBO therapy. The indications for HBO therapy were stroke in five patients, ileus in four patients, cancer in two patients, acute peripheral circulatory disturbance in two patients, and others in three patients. The mean observation period was 5.4 years.

Results

In the univariate analysis, there was no significant difference in severity, mortality, hospitalization, or overall survival between patients who did and did not receive HBO therapy. However, the HBO group had a significantly lower recurrence rate (0% vs. 22.4%, p=0.0363) and a shorter symptomatic period (6.2 vs. 13.6 days, p=0.0217).

Conclusions

HBO may have beneficial effect on CDI by shortening the symptomatic period and preventing recurrence.

The Host-Microbiome Response to Hyperbaric Oxygen Therapy in Ulcerative Colitis Patients

BACKGROUND & AIMS

Hyperbaric oxygen therapy (HBOT) is a promising treatment for moderate-to-severe ulcerative colitis. However, our current understanding of the host and microbial response to HBOT remains unclear. This study examined the molecular mechanisms underpinning HBOT using a multi-omic strategy.

METHODS

Pre- and post-intervention mucosal biopsies, tissue, and fecal samples were collected from HBOT phase 2 clinical trials. Biopsies and fecal samples were subjected to shotgun metaproteomics, metabolomics, 16s rRNA sequencing, and metagenomics. Tissue was subjected to bulk RNA sequencing and digital spatial profiling (DSP) for single-cell RNA and protein analysis, and immunohistochemistry was performed. Fecal samples were also used for colonization experiments in IL10-/- germ-free UC mouse models.

RESULTS

Proteomics identified negative associations between HBOT response and neutrophil azurophilic granule abundance. DSP identified an HBOT-specific reduction of neutrophil STAT3, which was confirmed by immunohistochemistry. HBOT decreased microbial diversity with a proportional increase in Firmicutes and a secondary bile acid lithocholic acid. A major source of the reduction in diversity was the loss of mucus-adherent taxa, resulting in increased MUC2 levels post-HBOT. Targeted database searching revealed strain-level associations between Akkermansia muciniphila and HBOT response status. Colonization of IL10-/- with stool obtained from HBOT responders resulted in lower colitis activity compared with non-responders, with no differences in STAT3 expression, suggesting complementary but independent host and microbial responses.

CONCLUSIONS

HBOT reduces host neutrophil STAT3 and azurophilic granule activity in UC patients and changes in microbial composition and metabolism in ways that improve colitis activity. Intestinal microbiota, especially strain level variations in A muciniphila, may contribute to HBOT non-response.

The composition of the human fecal microbiota might be significantly associated with fecal SCFA levels under hyperbaric conditions

The fecal microbiota and short-chain fatty acids (SCFAs) play important roles in the human body. This study examined how hyperbaric conditions affect the fecal microbiota and fecal SCFAs. Fecal samples were obtained from 12 divers at three points during deep-diving training (before the diving training, at 2.1 MPa, and after decompression). At 2.1 MPa, the changes in the frequency of Clostridium cluster IV and fecal iso-valerate levels were positively correlated, and the changes in the frequencies of Bacteroides and Clostridium subcluster XIVa were inversely correlated. After decompression, positive correlations were detected between the changes in the frequency of Bifidobacterium and fecal n-valerate levels and between the changes in the fecal levels of iso-butyrate and iso-valerate. On the other hand, inverse correlations were detected between the changes in the frequency of Clostridium cluster IX and fecal iso-butyrate levels, between the changes in the frequency of Clostridium cluster IX and fecal iso-valerate levels, and between the changes in the frequencies of Bacteroides and Clostridium cluster IV plus subcluster XIVa. During the study period, the changes in fecal iso-butyrate and iso-valerate levels were positively correlated, and inverse correlations were seen between the changes in the frequency of Clostridium cluster IV and fecal propionate levels and between the changes in the frequencies of Prevotella and Clostridium subcluster XIVa. These findings suggest that hyperbaric conditions affect the fecal microbiota and fecal SCFA levels and that intestinal conditions reversibly deteriorate under hyperbaric conditions.