Clostridium symbiosum

Clostridium symbiosum (Blautia symbiosum) is a gut bacterium with emerging clinical significance, particularly in colorectal cancer (CRC) and coronary artery disease (CAD). 

While it contributes to gut health by producing short-chain fatty acids, its altered abundance has been linked to disease states.

What is Clostridium symbiosum?

Clostridium symbiosum (Blautia symbiosum) is an anaerobic, Gram-positive gut bacterium. Though primarily a commensal organism, research has linked it to colorectal cancer (CRC), coronary artery disease (CAD), and, in rare cases, bacteremia.

Clostridium symbiosum (Blautia symbiosum) produces short-chain fatty acids (SCFAs) like butyrate, which support gut health. It also produces some branched-chain amino acids, although this is linked with CRC pathogenesis.

Originally classified under Clostridium, it has since been reclassified to the Blautia genus, though older literature still references its former name.

Role in Colorectal Cancer

C. symbiosum is enriched in CRC tumor tissues and associated with increased adenoma recurrence. It promotes tumorigenesis by producing branched-chain amino acids (BCAAs), which enhance cholesterol synthesis and activate Sonic Hedgehog (SHH) signaling, leading to increased cancer stemness. 

Fecal C. symbiosum may be valuable as a noninvasive biomarker for early CRC detection, outperforming conventional screening tools like FIT and carcinoembryonic antigen (CEA), according to one research paper.

Association with Coronary Artery Disease

Research indicates that C. symbiosum contributes to CAD by modulating bile acid metabolism and immune function, promoting the development of CAD. 

It promotes secondary bile acid production, disrupting cholesterol homeostasis and leading to vascular dysfunction. Additionally, it induces systemic inflammation through Th17 activation and gut barrier disruption, exacerbating arterial stiffness.

Rare Cases of Bacteremia

A single case report documented C. symbiosum bacteremia in a patient with metastatic colon cancer, highlighting its potential as an opportunistic pathogen in immunocompromised individuals. Due to its atypical Gram-negative staining, identification required 16S rRNA sequencing.

Clinical Implications

While C. symbiosum is not a routine clinical target, its role in CRC and CAD suggests potential for microbiota-based interventions. It may serve as a biomarker for disease risk assessment and a target for therapies aimed at modifying gut microbial composition.

Who Should Be Tested for Clostridium symbiosum?

C. symbiosum levels are mainly measured in microbiome research, not routine clinical practice. Studies assess its role in:

Inflammatory and Metabolic Conditions

Variability in C. symbiosum levels has been linked to colorectal cancer and coronary artery disease, and may influence metabolic issues.

Diet and Microbiome Interventions

Research that explores how diet, probiotics, and other interventions impact C. symbiosum and gut health may involve testing for C. symbiosum.

Testing for Clostridium symbiosum: Procedure and Interpretation

Testing for Clostridium symbiosum is typically done through stool sample analysis. This test can be conducted using various methods, such as PCR, next-generation sequencing (NGS), or culture-based techniques. 

A stool sample is collected and analyzed to quantify the presence of C. symbiosum. and assess its relative abundance compared to other gut bacteria.

Always consult the ordering provider or laboratory company prior to sample collection, as special preparation, such as avoiding antibiotics or probiotics, may be necessary in the days leading up to sample collection.

Normal Reference Range

Normal reference ranges for Clostridium symbiosum can vary based on the laboratory and the microbiome composition of the healthy population. Generally, the goal is to maintain a balanced ratio of Clostridium symbiosum alongside other beneficial gut flora.

Clinical Significance of Elevated Clostridium symbiosum

High C. symbiosum levels have been associated with the presence of blood in stool and have been investigated as a potential biomarker for colorectal cancer (CRC). Elevated levels may indicate disruptions in gut microbiome composition and could contribute to metabolic imbalances through altered butyrate production, changes in bile acid metabolism and lipid processing, or other microbial interactions.

Clinical Significance of Decreased Clostridium symbiosum

Low C. symbiosum levels may reflect a reduction in certain butyrate-producing bacteria, which can negatively impact gut barrier integrity and overall colonic health. 

Since butyrate is essential for colonocyte function and anti-inflammatory responses, a decrease in C. symbiosum could be linked to inflammatory bowel conditions or dysbiosis-related disorders.

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