The Bacteria That Controls Our Health

As doctors, we treat the patient and their symptoms. We treat them in isolation, as a person, their symptoms, medication to target their heart, lungs, kidney and so on. But we are not alone. In fact, each of us is outnumbered. Living on us and inside us are billions and trillions of little microorganisms. Bacteria, fungi, viruses, they live in our skin, our gut, our lungs, and they appear to play a large part in the diseases that affect us. Cancer, autoimmune disorders, even neurological disorders like Parkinson’s Disease.

Here we will talk a bit about the bacteria in your gut, and how they can affect you and the diseases you have.

YOUR GUT AND CANCER

The gut microbiome is becoming an increasingly more important and recognised part of our health, with some professionals going as far as calling it the last discovered organ. Evermore research has gone into understanding how the complex mix of bacteria and other microbes interact and influence our health.

One of the most famous examples was the discovery of a bacteria called Helicobacter pylori that resides in our stomach. Previously it was thought stress was the key cause for stomach ulcers. Two Australian researchers discovered screw shaped bacteria in the lining of ulcers and insisted that a simple mix of antibiotics could cure this common illness, but their explanation fell on deaf ears. To prove the critics wrong, one researcher drank a broth of this bacteria, giving himself ulcers as a direct result, and soon claimed the Nobel Prize. Not all links between gut bacteria and disease are this simple, however.

Recent research has shown that many bacteria present in our gut biome may have a role in cancer. Some produce DNA damaging toxins, carcinogenic metabolites, promote cancer through inflammation and even make tumours more resistant to chemotherapy drugs.

One bacteria, B fragilis, a known cause of diarrhoea in young children, was found to increase the development of bowel cancer by calling immune cells to the gut lining and creating inflammation that would lead to an increased risk of cancer. E coli can damage DNA through toxins F nucleatum helps proliferate cancer cells in the gut. 

Comparing the gut bacteria in different auto-immune diseases has also shown there to be associations between some species of bacteria and immune conditions. Similarly, the presence of some types of bacteria has been shown to have an anti-inflammatory effect.

It is thought in this case that the proteins made by the offending bacteria are too similar to some human proteins, and cause confusion for the body’s immune cells. They become activated against the bacteria, but inadvertently target human cells and proteins that to them appear similar to the bacteria. A lack of tolerance and a pro-inflammatory state is driven by these gut bacteria can be a serious issue.

GOOD NEWS

It's not all doom and gloom with bacteria, however. We know they play an extremely important part in keeping us healthy as well as sometimes causing disease. In hospitals, we often give patients extremely strong antibiotics to treat their infection. Unfortunately, this can destroy the bacteria in our gut. This leads to the rampant proliferation of a bacteria known as C difficile, leading to severe inflammation of the gut, diarrhoea and significantly worse outcomes for the patient.

Treating this condition can be very difficult, as it might need further antibiotics, stronger antibiotics, and it can be very uncomfortable for the patient. One proposed treatment was faecal transplant. A crazy idea of transferring faeces from a healthy patient to one with C diff colitis. Except this crazy theory proved to be too good, much better than the conventional antibiotic therapy. The trial was stopped as it was unethical to withhold the faecal transplant from the control group, and everyone was given the treatment to help them recover.

Scientists are now working on specific blends of bacteria to treat certain conditions. Some have even engineered bacteria with specific functions. A team in Singapore have created a strain of bacteria that can secrete an enzyme that converts natural substances in digested vegetables in the gut to molecules that can inhibit tumour growth. This was shown to help shrink colon cancer tumours in mice.

Another team even demonstrated bacteria that could sense signs of a disease, for instance, growth of bacteria known to cause harm, and in turn produce antimicrobial substances to destroy that bacteria. It had success in clearing infections in worms and mice. Another team designed bacteria that could sense signs of inflammatory bowel disease, and produce a marker protein that can be detected in the patient's stools. Such tests could help diagnose a notoriously tricky condition that affects many people.

EXPECTATIONS

Of course its tricky to make such bacteria, and can be even trickier to test its safety in patients. The insight into microbiomes above is not meant to influence current treatment, but instead, show a guide of what we could expect in the future. It is an exploration of how our knowledge is advancing and looking beyond the obvious, beyond what is in front of us, and instead of understanding every part of our body is in a relationship with itself, the microbes that colonise it, and the environment we interact with. Looking beyond the obvious can help us finally understand how complex diseases initiate, propagate, and hopefully how they can be managed or even treated.

It's interesting how the bacteria in our gut is a good place to start.