Food isn’t the only thing in your stomach
Katrina Stefanik (12:00 Micro) found this news article via Science Daily describing how a bacterium can cause disease in the human stomach, and probably NOT a disease you were thinking of. Some of her background information came from the National Cancer Institute’s website as well. Here is an article I found about Helicobacter pylori that tells a little bit different story; it seems that H. pylori in the human gut can act to suppress the appetite, which suggests that reduction of the numbers of this bacteria might be linked to increases in childhood obesity. Remember folks–in medicine we like to have nice, neat little connections between things, however in reality the interactions between things are FAR more complicated that you might imagine. Here is Katrina’s report:
Microbiology is making me wary of all these little microbes running around and infecting everything and everybody with their diseases! Now I know, Dr. Singleton, that you mentioned not all microbes are negative, as our textbook unfortunately portrays…but I’m not really getting a welcoming feeling from these little guys! Something that caught my attention as I was browsing the internet talked about wonderful stomach bacteria which compromise the human immune system to trigger disease. It is better known as Helicobacter pylori and creates life-long stomach infections such as duodenal ulcers or stomach cancer.
The human stomach is a very acidic place in the body, but H. pylori are clever bacteria. In order to survive the adverse conditions of the stomach, H. pylori emit an enzyme better known as urease. Urease converts the chemical urea to ammonia; this neutralizes the acidity of the stomach. The bacterium is then able to survive in this environment. H. pylori also demonstrates a helical shape (Helico=helical!), which allows it to bury into a less acidic mucus layer of the stomach. Our immune cells do recognize this foreigner, but since it is in the stomach, they are unable to reach it.
Healthy bodies produce an antimicrobial component in the stomach lining called ‘human beta defensin 1’; these guys assist in preventing bacterial infection. When 54 stomach tissue biopsies were taken from at the Queens Medicle Centre in Nottingham, it was found that diseased patients with H. pylori had TEN times less ‘human beta defensin 1’ than healthy patients! The patients with the highest amount of bacteria in their stomach lining also demonstrated a low amount of the ‘human beta defensin 1.’ So what does this mean? It is obvious that H. pylori must repress the making of our bacteria-fighting soldiers.
In a unique process, H. pylori creates cagT4SS; this is a molecular ‘syringe’ in which bacterial products are instilled into the stomach lining cells. After this injection, chemical pathways are activated to decrease ‘human beta defensin 1’ creation. Oh- it gets better. As if that wasn’t good enough for the bacteria, they found that the same activated pathways are involved in the stimulation of an inflammatory response. What this entails is that while bacterial strains are flourishing under favorable conditions and diseasing us, they are also causing us tissue damage.
According to the article, more than half the of world’s population contain H. pylori. It is quite troubling to think that probably someone in my immediate or extended family has this bacteria hanging around in the mucosal lining of their stomach. Heck- it might even be me! Fortunately, for most people, the infection is asymptomatic. This means that there are carriers of the disease, but these people are not experiencing the symptoms or implications. Phew! However, 1-2 percent of the infected will develop gastric cancer. When gastric cancer becomes apparent to the patient, it is often too late and the cancer is too far developed. Because of this, survival rates are seemingly very low.
I definitely enjoyed reading about this and talking about it. As a future nurse, this makes me much more appreciative of these microscopic organisms and their enormous effect on patients.