Stomach Microflora: Helicobacter and Bacteria
Author: Thomas C. Weiss : Contact: Disabled World
Information regarding Helicobacter pylori, a Gram-negative, micro-aerophilic bacterium found in the stomach.
The fact that around 50% of the people in the world are infected with the stomach bacteria called, 'Helicobacter pylori,' or, 'H. pylori,' is perhaps astounding, yet it causes disease in only about 10% of the people infected. Additional bacteria living in people's stomachs might be a key factor in whether or not H. pylori causes disease according to a study led by scientists at the University of California, Santa Cruz. Karen Ottemann, Professor and Chair of microbiology and environmental toxicology at U.C. Santa Cruz stated, "People tend to think of the stomach as a relatively sterile environment, but it's actually populated with microbes."
Helicobacter - A genus of Gram-negative bacteria possessing a characteristic helical shape. They were initially considered to be members of the Campylobacter genus. The Helicobacter genus contains about 35 species.
Helicobacter Pylori - Previously named Campylobacter pylori, is a Gram-negative, microaerophilic bacterium found in the stomach, and may be present in other parts of the body, such as the eye.
Researchers in Karen's laboratory were studying H. Pylori infections in mice when they noticed that mice from two different suppliers had different responses to the infection - even though they were the same strain of mouse and therefore genetically identical. Examining the bacteria in the stomachs of mice or, 'stomach microflora,' they found differences between the mice from different suppliers. The researchers then used antibiotics to alter the stomach microflora in mice from a single supplier; again - they again found changes in response to H. pylori. Karen said, "We found that something about the pre-existing microflora, before H. pylori comes into the mouse, changes the mouse's response to the infection."
The findings were published in the journal, 'Infection and Immunity,' and have potential implications for treatment of human infections. The bacteria in the stomachs of mice and people are broadly the same, not necessarily at the species level, yet the same types of bacteria are present in both according to Karen. H. pylori infections can cause ulcers and stomach cancer, although the majority of those infected do not develop any disease.
There is also evidence that H. pylori may protect against diseases such as asthma and esophageal cancer. Due to these reasons, people are only treated for the infection if they develop symptoms of it. With an increased understanding of the effects of the stomach microflora, it may be possible to predict whether someone is likely to develop disease and should be treated for an H. pylori infection. Karen said, "It would be nice if we could predict who would get disease. The other possibility is that we might be able to identify some bacteria that could be used as a probiotic to dampen H. pylori disease."
At this time, it remains unclear which bacteria are responsible for changing the response to H. pylori infections in mice. Concentrating on mice from a single supplier, Karen's team used genetic profiling techniques to identify greater than ten-thousand types of bacteria present in the stomachs of mice, of which around two-thousand were found in all of the mice they sampled. The researchers treated some of the mice with antibiotics, which did not eliminate stomach bacteria - yet substantially changed the composition of the stomach microflora.
The altered microflora dampened the inflammatory response to H. pylori infection. When researchers looked for differences in the stomach microfloras of mice with and without inflammatory disease, they discovered more than four-thousand differences; either species present in one group and not another, or differences in the abundances of certain species. Additional work is required to identify which differences in bacterial composition are responsible for the differences in response to H. pylori. Karen stated, "The results do point to some potential candidates for a protective effect, such as Clostridium species, some of which are known to influence inflammation in the intestine."
Helicobacter pylori - A Specialized Bacteria
There are only a few bacteria specialized to survive in a person's stomach. For the majority of other bacteria, the stomach is a bottle neck and the majority will perish when they stay inside the stomach for too long, or when pH is too low. Food particles; however, may temporarily increase the pH so that bacteria can sneak through with a meal someone has consumed. In this manner, food-borne pathogens reach a person's intestines, where they are fine.
The few bacteria that have the ability to survive in a person's stomach produce specific enzymes that increase the pH around them. Helicobacter pylori is the only example proven stomach bacteria so far to live preferentially in the stomach. The enzyme they produce is Urease. They have the ability to survive long enough to reach the epithelial cells that line a person's stomach and they live in the niches between these cells. The pH of these niches is fairly neutral so while the stomach bacteria can survive the acidity - they would rather get away from it entirely.
The medications a person is prescribed to get rid of H. pylori are antibiotics. The antibiotics have specific antibacterial activity and kill the bacteria without harming an person's stomach tissue. Antibiotics are acid-resistant.
Helpful and Harmful Bacteria
Bacteria usually linked to stomach ulcers and even cancer might turn out to actually protect people from infections that are dangerous. Diarrheal diseases kill thousands of children every single year - mainly in developing countries. German scientists are suggesting that the stomach bacteria H. pylori, which is carried by a large portion of the human population from childhood through the rest of life, might help a person's body to fight off the other bugs that cause them.
Over the past several years, H. pylori has become recognized as one of the most common human pathogens. H. pylori colonize the gastric mucosa of nearly everyone exposed to poor hygienic conditions from childhood. It also is often found with a lower frequency in groups of high socioeconomic status. The stomach bacteria H. pylori causes chronic active gastritis and is a major factor in the pathogenesis of duodenal ulcers and - to a lesser extent, gastric ulcers. The presence of this bacterium is now recognized as a risk factor for lymphoma and gastric adenocarcinoma. Despite these facts, the majority of infections people experience appear without clinical consequences.
- H. pylori is of primary importance for medicine, but non-pylori Helicobacter species (NPHS), which naturally inhabit mammals (except humans) and birds, have been detected in human clinical specimens.
- At least half the world's population is infected by the H. pylori bacterium, making it the most widespread infection in the world.
- Up to 85% of people infected with H. pylori never experience symptoms or complications.
- Acute infection may appear as an acute gastritis with abdominal pain (stomach ache) or nausea. Where this develops into chronic gastritis, the symptoms, if present, are often those of non-ulcer dyspepsia: stomach pains, nausea, bloating, belching, and sometimes vomiting or black stool.
- H. pylori is contagious, although the exact route of transmission is not known.
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