When Does Commensal Flora Matter?

Introduction

Hello, my name is Dr. Cheryl Burdette. I'm the clinical director of Origins Incubator. Today, we looked at some of the nuances around stool testing. One of the things we delve into is “What should we do when we order a stool test (because we feel that this might be the reason for a patient’s symptoms, such as abdominal pain, constipation, bloating) and what we get back is something that shows no pathogens, no bacteria that pathogenic bacteria is present, but an imbalance of commensal flora?” How meaningful is that to us? 

Commensal Flora

We've all seen this issue. Maybe we have somebody who's highly symptomatic, or for sure there's going to be a big bad pathogen that comes back. When we ordered the test, what we actually see is there's the absence of a pathogen, but some flora that can be normal, yet might be overgrowing. And, how associated is this with pathology? Could it be responsible for significant symptoms, even though it's an imbalance of relatively normal flora? 

A Reason for Pathology

The answer to that can be a yes. The reason for that is because it's not always about just the bacteria itself, but what it produces. And when we see an overgrowth of imbalanced flora, it's often gram-negative bacteria, and it's often producers of lipopolysaccharides (LPS). Even if you're not that bad of a bacterium, but you are overgrowing, now there's too much LPS, and that lipopolysaccharide, as we know is, of course, a toxin, a metabolic toxin, responsible for metabolic endotoxemia. This can damage lipids and be the reason they're oxidized, can damage the heart and be the reason that there's damage there, and can damage insulin receptors and contribute to insulin resistance. So absolutely, there can be a reason for pathology. 

Autoimmunity

And, of course, another big player that LPS plays a role is in terms of autoimmunity. It increases things like toll-like receptors, so that the immune system is more inflamed. Those receptors can even be increased on the GI mucosa itself, making the mucosal lining even more reactive. In addition to that, those lipopolysaccharides can decrease the activity of Regulatory T Cells (Treg). Treg cells are the ones that put the immune system back in balance. A hallmark of many autoimmune conditions is that these Treg functions are low. 

Conclusion

So, we wrestled with questions like imbalance of normal bacteria or commensal flora and thought about which conditions can have a greater impact in guiding us to know when to prioritize it clinically.

If you would like to join in on these helpful conversations, contact us anytime at Origins Incubator.