A lot, and almost nothing.
The microbiome is the vast population of microorganisms (mainly bacteria) that live in a site like the intestinal tract, respiratory tract or on the skin. While we often think about bacteria as causes of disease, they’re also critical for our survival. The overall population of microorganisms (the microbiome) provides many benefits to the host (be it a person or animal), but how it interacts with the body is complex and poorly understood.
I’ve been working on microbiota for quite a few years and I think I understand a fair bit about it, but I also think I understand little about it in the grand scheme of things. People often think it’s this cutting edge new technology (it is) that can tell us a lot about ourselves or our patients (it can) and guide medical decisions (not yet). The problem is, there’s a difference between information and knowledge. If you give me a fecal sample (or sample from any other site), I can tell you lots about what’s in it. I can tell you how that fits on a population level with normal or healthy groups. But, I can’t say much with confidence about that individual.
While we’re getting more and more information about the microbiome in healthy and sick animals and people, we don’t really know what we’re looking at. There’s a wide variety of “normal” microbiomes, not just one. If you take 100 healthy dogs and 100 dogs with inflammatory bowel disease, there will be some clear differences between the overall groups. However, some of the sick dogs will have microbiomes that look just like normal dogs, and some perfectly healthy individuals will have microbiomes that I’d consider completely screwed up.
Also, while we get reams of data, and there are lots of ways to analyse them, we still don’t really know what the most important elements are. Is it the overall richness (number of different bacterial species)? Their diversity? The presence of specific bugs? Ratios of specific bugs or groups?
There are still many other issuses as well. For example, does a single sample tells us the whole story? Do data from one geographic region apply to another? Do we need to account for diet, age and various other factors? Should a healthy vegan’s microbiota, for example, be expected to be the same as a healthy meat eater? How good is testing feces when disease occurs higher up in the intestinal tract?
Lots of questions still need answers. This isn’t meant to dismiss the importance of the field. Like many other groups, we continue to work to try to figure out the microbiome. However, we need to make sure we stay grounded and remember how little we actually “know”.
You can pay to get your dog’s (or your) microbiome tested, get recommendations about whether it’s “normal,” and sometimes be sold treatments as a result of that interpretation. You can buy products to “protect” your microbiome (without much or any evidence behind them). However, remember that marketing often outpaces evidence.
The microbiome’s a wonderful thing. I can’t wait until we understand it better.