Helicobacter pylori

Helicobacter pylori is a species of gram-negative bacteria that lives in the human stomach.

It belongs to the Helicobacter genus and is famous for its ability to survive in very harsh environments. While over half of the global population is infected, many people remain asymptomatic, meaning they show no signs of illness. However, certain virulent strains can cause serious health issues by colonizing the stomach lining. This bacterium is unique because it is the only known bacterium capable of causing cancer.

To survive the stomach's intense acidity, H. pylori uses several specialized biological mechanisms. Its body has a helical or spiral shape, which helps it move through the thick, viscous mucus layer.

The bacteria use flagella, which are tail-like structures, to swim through this protective mucus. Once they reach the less acidic areas, they use a protein called urease to help them thrive. Urease is a major component of the bacterium, representing about 10% of its total protein weight.

This enzyme allows the bacteria to manage the environment around them.

The infection often progresses through several distinct stages known as Correa's cascade. It typically begins with gastritis, which is the inflammation of the stomach lining. If the infection is not cleared, it can become chronic gastritis. This prolonged inflammation can lead to atrophic gastritis, where the stomach lining begins to thin. Eventually, this damage can result in peptic ulcers in the stomach or the duodenum, which is the first part of the small intestine.

At the final stages, the risk of developing gastric cancer becomes significantly higher.

For many years, the cause of stomach ulcers was a mystery to the medical community. While some researchers like John Lykoudis had noted links between bacteria and ulcers, the true cause was not formally proven until later. In 1983, Australian physician-scientists Barry Marshall and Robin Warren described H. pylori as the causal agent of gastric ulcers.

Their work changed how doctors treat digestive diseases. Because of this monumental discovery, Marshall and Warren were awarded the Nobel Prize in Physiology or Medicine in 2005.

The impact of H. pylori on global health is significant and measurable. It is estimated that the bacterium is responsible for approximately 89% of all gastric cancers. Furthermore, it is linked to 5.5% of all cancer cases worldwide. While many people carry the bacteria without issue, about 1% to 3% of infected individuals will develop gastric cancer in their lifetime. This is much higher than the 0.13% rate seen in people without the infection.

Because the infection often lacks symptoms, many cases of gastric cancer are diagnosed at an advanced stage.

Beyond cancer, H. pylori is linked to various other medical conditions. These extragastric complications include anemia caused by iron or vitamin B12 deficiencies. It has also been linked to diabetes mellitus, cardiovascular illness, and certain neurological disorders. Interestingly, the relationship between the bacterium and the body is complex. Some studies suggest an inverse association, meaning the bacteria might offer a protective effect against asthma, esophageal cancer, or inflammatory bowel disease.

Some researchers even believe non-pathogenic strains might help regulate appetite or stomach acid.

Modern science continues to study the complex genome and biology of this bacterium. The genome of the 26695 strain contains about 1.7 million base pairs and 1,576 genes. Scientists use tools like single-cell transcriptomics to understand how the bacteria turn certain genes on or off.

In 2023, it was estimated that two-thirds of the world's population was infected, though this number is declining. This decline is due to better living standards and medical treatments, such as antibiotics and proton-pump inhibitors. By studying these tiny organisms, researchers hope to better manage their effects on human health.